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Homocysteine‐lowering interventions for preventing cardiovascular events

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References

References to studies included in this review

BVAIT 2009 {published data only}

Hodis HN, Mack WJ, Dustin L, Mahrer PR, Azen SP, Detrano R, BVAIT Research Group. High‐dose B vitamin supplementation and progression of subclinical atherosclerosis: a randomized controlled trial. Stroke 2009;40(3):730‐6. [PUBMED: 19118243]

CHAOS 2002 {published data only}

Baker F, Picton D, Blackwood S, Hunt J, Erskine M, Dyas M, et al. Blinded comparison of folic acid and placebo in patients with ischaemic heart disease: an outcome trial. Circulation 2002;106(Suppl II):741.

FOLARDA 2004 {published data only}

Liem AH, van Boven AJ, Veeger NJ, Withagen AJ, Robles de Medina RM, Tijssen JG, et al. Efficacy of folic acid when added to statin therapy in patients with hypercholesterolemia following acute myocardial infarction: a randomised pilot trial. International Journal of Cardiology 2004;93:175‐9. [PUBMED: 14975544 ]

GOES 2003 {published data only}

Liem A, Reynierse‐Buitenwerf GH, Zwinderman AH, Jukema JW, van Veldhuisen DJ. Secondary prevention with folic acid: effects on clinical outcomes. Journal of the American College of Cardiology 2003;41:2105‐13. [PUBMED: 12821232]
Liem A, Reynierse‐Buitenwerf GH, Zwinderman AH, Jukema JW, van Veldhuisen DJ. Secondary prevention with folic acid: results of the Goes extension study. Heart 2005;91:1213‐4. [PUBMED: 16103563]

HOPE‐2 2006 {published data only}

Lonn E, Held C, Arnold JM, Probstfield J, McQueen M, HOPE‐2 Investigators. Rationale, design and baseline characteristics of a large, simple, randomized trial of combined folic acid and vitamins B6 and B12 in high‐risk patients: the Heart Outcomes Prevention Evaluation (HOPE)‐2 trial. Canadian Journal of Cardiology 2006;22(1):47‐53. [PUBMED: 16450017]
Lonn E, Yusuf S, Arnold MJ, Sheridan P, Pogue J, Micks M, et al. Homocysteine lowering with folic acid and B vitamins in vascular disease. New England Journal of Medicine 2006;354:1567‐77. [PUBMED: 16531613]
Saposnik G, Ray J, Sheridan P, McQueen M, Lonn E. Homocysteine lowering therapy and stroke risk, severity and disability: results from the HOPE‐2 trial. Stroke 2009;40(4):e131. [DOI: 10.1161]
Saposnik G, Ray JG, Sheridan P, McQueen M, Lonn E, Heart Outcomes Prevention Evaluation Investigators. Homocysteine‐lowering therapy and stroke risk, severity, and disability: additional findings from the HOPE 2 trial. Stroke2009; Vol. 40, issue 4:1365‐72. [PUBMED: 19228852]

NORVIT 2006 {published data only}

Bonaa KH, Njolstad I, Ueland PM, Schirmer H, Tverdal A, Steigen T, et al. Homocysteine lowering and cardiovascular events after acute myocardial infarction. New England Journal of Medicine 2006;354:1578‐88. [PUBMED: 16531614]

SEARCH 2010 {published data only}

Armitage JM, Bowman L, Clarke RJ, Wallendszus K, Bulbulia R, Study of the Effectiveness of Additional Reductions in Cholesterol and Homocysteine (SEARCH) Collaborative Group. Effects of homocysteine‐lowering with folic acid plus vitamin B12 vs placebo on mortality and major morbidity in myocardial infarction survivors: a randomized trial. JAMA 2010;303:2486‐94. [PUBMED: 20571015]
Clinical Trial Service Unit & Epidemiological Studies Unit. SEARCH Study Protocol. https://www.ctsu.ox.ac.uk/research/research‐archive/searchs/search‐study‐protocol/view (accessed 7 January 2015):1‐36.
Group Search Collaborative. Study of the Effectiveness of Additional Reductions in Cholesterol and Homocysteine (SEARCH) Collaborative Group. Intensive lowering of LDL cholesterol with 80 mg versus 20 mg simvastatin daily in 12 064 survivors of myocardial infarction: a double‐blind randomised. Lancet 2011;377(9760):126. [PUBMED: 21067805]

SU.FOL.OM3 2010 {published data only}

Andreeva VA, Touvier M, Kesse‐Guyot E, Julia C, Galan P, Hercberg S. B vitamin and/or ω‐3 fatty acid supplementation and cancer: ancillary findings from the supplementation with folate, vitamins B6 and B12, and/or omega‐3 fatty acids (SU.FOL.OM3) randomized trial. Archives of Internal Medicine 2012;172(7):540‐7. [PUBMED: 22331983]
Blacher J, Czernichow S, Paillard F, Ducimetiere P, Hercberg S, Galan P, on behalf of the SU.FOL.OM3 Study Research Group. Cardiovascular effects of B‐vitamins and/or N‐3 fatty acids: the Su.Fol.OM3 trial. International Journal of Cardiology 2013;167(2):508‐13. [PUBMED: 22365647]
Galan P, Briancon S, Blacher J, Czernichow S, Hercberg S. The SU.FOL.OM3 Study: a secondary prevention trial testing the impact of supplementation with folate and B‐vitamins and/or Omega‐3 PUFA on fatal and non fatal cardiovascular events, design, methods and participants characteristics. Trials 2008;9:35. [PUBMED: 18544171]
Galan P, Briancon S, Blacher J, Czernichow S, Hercberg S. The scientific basis of the SU.FOL.OM3 study: a secondary intervention trial of folate, B6 and B12 vitamins and/or omega 3 fatty acid supplements in the prevention of recurrent ischemic events [Bases scientifiques de l’étude SUFOLOM3: essai de prévention secondaire visant à tester l’impact d’une supplémentation en folates, vitamines B6 et B12 et/ou acides gras oméga‐3 dans la prévention de la récidive de pathologies ischémiques]. Sang Thrombose Vaisseaux 2009;21(4):207‐13. [ISSN 0999‐7385]
Galan P, Kesse‐Guyot E, Czernichow S, Briancon S, Blacher J, Hercberg S. Effects of B vitamins and omega 3 fatty acids on cardiovascular diseases: a randomised placebo controlled trial. BMJ 2011;342:36. [ISSN 0959‐8146]
Galan P, Kesse‐Guyot E, Czernichow S, Briancon S, Blacher J, Hercberg S, SU.FOL.OM3 Collaborative Group. Effects of B vitamins and omega 3 fatty acids on cardiovascular diseases: a randomised placebo controlled trial. BMJ 2010;341:1‐9. [PUBMED: 21115589]
Galan P, de Bree A, Mennen L, Potier de Courcy G, Preziozi P, Bertrais S, et al. Background and rationale of the SU.FOL.OM3 study: double‐blind randomized placebo‐controlled secondary prevention trial to test the impact of supplementation with folate, vitamin B6 and B12 and/or omega‐3 fatty acids on the prevention of recurrent ischemic events in subjects with atherosclerosis in the coronary or cerebral arteries. Journal of Nutrition, Health & Aging 2003;7(6):428‐35. [PUBMED: 14625623]
Szabo de Edelenyi F, Vergnaud AC, Ahluwalia N, Julia C, Hercberg S, Blacher J, et al. Effect of B‐vitamins and n‐3 PUFA supplementation for 5 years on blood pressure in patients with CVD. British Journal of Nutrition 2012;107(6):921‐7. [PUBMED: 21801476]
Vesin C, Galan P, Gautier B, Czernichow S, Hercberg S, Blacher J. Control of baseline cardiovascular risk factors in the SU‐FOL‐OM3 study cohort: does the localization of the arterial event matter?. European Journal of Cardiovascular Prevention and Rehabilitation 2010;17(5):541‐8. [PUBMED: 20216318]

VISP 2004 {published data only}

Elias GA, Patel RK, Chen WM, Mychaleckyj JC, Hsu FC, Worrall BB, et al. Association of a transcobalamin 2 (TCN2) variant located in the 3UTR with post‐stroke homocysteine level in subjects from the vitamin intervention for stroke prevention trial. Stroke. 2010; Vol. 41(4):e335. [ISSN 0039‐2499]
Elkhatib SD, Hsu FC, Pemberton BL, Sale MM, Worrall BB. Sex differences in genetic associations with homocysteine in the vitamin intervention for stroke prevention (VISP) trial. Stroke 2011;42(3):e187. [ISSN 0039‐2499]
Sale MM, Hsu FC, Mychaleckyj JC, Rich SS, Furie KL, Worrall BB. A variant in the adenosine 2B receptor gene is associated with homocysteine levels and stroke severity in African American subjects from the vitamin intervention for stroke prevention (VISP) trial. Stroke 2010;41(4):e334. [ISSN: 0039‐2499]
Spence JD, Bang H, Chambless LE, Stampfer MJ. Vitamin intervention for stroke prevention trial: an efficacy analysis. Stroke 2005;36(11):2404‐9. [PUBMED: 16239629]
Toole JF, Malinow MR, Chambless LE, Spence JD, Pettigrew LC, Howard VJ, et al. Lowering homocysteine in patients with ischemic stroke to prevent recurrent stroke, myocardial infarction, and death: the Vitamin Intervention for Stroke Prevention (VISP) randomized controlled trial. JAMA 2004;291:565‐75. [PUBMED: 14762035]

VITATOPS 2010 {published data only}

Cavalieri M, Schmidt R, Chen C, Mok V, de Freitas GR, Song S, et al. B vitamins and magnetic resonance imaging‐detected ischemic brain lesions in patients with recent transient ischemic attack or stroke: the VITAmins TO Prevent Stroke (VITATOPS) MRI‐substudy. Stroke 2012;43(12):3266‐70. [PUBMED: 23093615]
Dusitanond P, Eikelboom JW, Hankey GJ, Thom J, Gilmore G, Loh K, et al. Homocysteine‐lowering treatment with folic acid, cobalamin, and pyridoxine does not reduce blood markers of inflammation, endothelial dysfunction, or hypercoagulability in patients with previous transient ischemic attack or stroke: a randomized substudy of the VITATOPS trial. Stroke 2005;36(1):144‐6. [PUBMED: 15569860]
Group Vitatops Study. The VITATOPS (VITAmins TO Prevent Stroke) trial: rationale, design and progress of an international, large simple, randomised trial of homocysteine‐lowering multivitamin therapy in patients with recent transient attack or stroke [Abstract]. Internal Medicine Journal. 2007; Vol. Suppl 4:A110.
Hankey GJ. The vitamins to prevent stroke (VITATOPS) trial: results of a double‐blind, placebo‐controlled, randomised trial of B‐vitamin therapy in 8,164 patients with recent transient ischaemic attack or stroke. Cerebrovascular Diseases. 2010; Vol. 29:11. [DOI: 10.1159/000321266]
Hankey GJ, Eikelboom JW, Yi Q, Lees KR, Chen C, Xavier D, et al. Treatment with B vitamins and incidence of cancer in patients with previous stroke or transient ischemic attack: results of a randomized placebo‐controlled trial. Stroke 2012;43(6):1572‐7. [PUBMED: 22474057]
Potter K, Hankey GJ, Green DJ, Eikelboom J, Jamrozik K, Arnolda LF. The effect of long‐term homocysteine‐lowering on carotid intima‐media thickness and flow‐mediated vasodilation in stroke patients: a randomized controlled trial and meta‐analysis. BMC Cardiovascular Disorders 2008;8:24. [PUBMED: 18803866]
Potter K, Lenzo N, Eikelboom JW, Arnolda LF, Beer C, Hankey GJ. Effect of long‐term homocysteine reduction with B vitamins on arterial wall inflammation assessed by fluorodeoxyglucose positron emission tomography: a randomised double‐blind, placebo‐controlled trial. Cerebrovascular Diseases 2009;27(3):259‐65. [PUBMED: 19202330]
Saposnik G. The role of vitamin B in stroke prevention: a journey from observational studies to clinical trials and critique of the VITAmins TO Prevent Stroke (VITATOPS). Stroke 2011;42(3):838‐42. [PUBMED: 21273566]
The VITATOPS Trial Study Group. B vitamins in patients with recent transient ischaemic attack or stroke in the VITAmins TO Prevent Stroke (VITATOPS) trial:a randomised, double‐blind, parallel, placebo‐controlled trial. Lancet Neurology 2010;9(9):855–65. [PUBMED: 20688574]
VITATOPS Trial Study Group, Hankey GJ, Algra A, Chen C, Wong MC, Cheung R, et al. VITATOPS, the VITAmins TO prevent stroke trial: rationale and design of a randomised trial of B‐vitamin therapy in patients with recent transient ischaemic attack or stroke (NCT00097669) (ISRCTN74743444). International Journal of Stroke 2007;2(2):144‐50. [PUBMED: 18705976]

WAFACS 2008 {published data only}

Albert CM, Cook NR, Gaziano JM, Zaharris E, MacFadyen J, Danielson E, et al. Effect of folic acid and B vitamins on risk of cardiovascular events and total mortality among women at high risk for cardiovascular disease: a randomized trial. JAMA 2008;299(17):2027‐36. [PUBMED: 18460663]
Glynn RJ, Manson JE, Women’s Antioxidant and Folic Acid Cardiovascular Study Group. Effect of folic acid and B vitamins on the occurrence of venous thromboembolism: a randomized trial in women at high cardiovascular risk. Circulation 2008;118:S1137.
Redbeg RF, Block PC. A randomized trial of folic acid and B‐vitamins in the secondary prevention of cardiovascular events in women: results from the Women's Antioxidant and Folic Acid Cardiovascular Study (WAFACS). ACC Cardiosource Review Journal 2006;16(7):52‐8.
Song Y, Cook NR, Albert CM, Van Denburgh M, Manson JE. Effect of homocysteine‐lowering treatment with folic acid and B vitamins on risk of type 2 diabetes in women: a randomized, controlled trial. Diabetes 2009;58(8):1921‐8. [PUBMED: 19491213]
Song Y, Cook NR, Albert CM, Van Denburgh M, Manson JE. Effect of homocysteine‐lowering treatment with folic acid and B vitamins on risk of type 2 diabetes mellitus in women: a randomized controlled trial. Circulation. 2009; Vol. 119:E273. [ISSN 0009‐7322]
Zhang SM, Cook NR, Albert CM, Gaziano JM, Buring JE, Manson JE. Effect of combined folic acid, vitamin B6, and vitamin B12 on cancer risk in women: a randomized trial. JAMA 2008;300(17):2012‐21. [PUBMED: 18984888]

WENBIT 2008 {published data only}

Bleie Ø, Strand E, Ueland PM, Vollset SE, Refsum H, Igland J, et al. Coronary blood flow in patients with stable coronary artery disease treated long term with folic acid and vitamin B12. Coronary Artery Disease 2011;22(4):270‐8. [PUBMED: 21389855]
Ebbing M, Bleie Ø, Ueland PM, Nordrehaug JE, Nilsen DW, Vollset SE, et al. Mortality and cardiovascular events in patients treated with homocysteine‐lowering B vitamins after coronary angiography: a randomized controlled trial. JAMA 2008;300:795‐804. [PUBMED: 18714059]
Ebbing M, Bonaa KH, Arnesen E, Ueland PM, Nordrehaug JE, Rasmussen K, et al. Combined analyses and extended follow‐up of two randomized controlled homocysteine‐lowering B‐vitamin trials. Journal of Internal Medicine 2010;268(4):367‐82. [PUBMED: 20698927]
Loland KH, Bleie O, Blix AJ, Strand E, Ueland PM, Refsum H, et al. Effect of homocysteine‐lowering B vitamin treatment on angiographic progression of coronary artery disease: a Western Norway B Vitamin Intervention Trial (WENBIT) substudy. American Journal of Cardiology 2010;105(11):1577‐84. [PUBMED: 20494665]

References to studies excluded from this review

Bazzano 2006 {published data only}

Bazzano LA, Reynolds K, Holder KN, He J. Effect of folic acid supplementation on risk of cardiovascular diseases: a meta‐analysis of randomized controlled trials. JAMA 2006;296:2720‐6.

Clarke 2010 {published data only}

Clarke R, Halsey J, Lewington S, Lonn E, Armitage J, Manson JAE, for the B‐Vitamin Treatment Trialists’ Collaboration. Effects of lowering homocysteine levels with B vitamins on cardiovascular disease, cancer, and cause‐specific mortality: Meta‐analysis of 8 randomized trials involving 37 485 individuals. Archives of Internal Medicine 2010;170(18):1622‐31. [PUBMED: 20937919]

Cui 2010 {published data only}

Cui R, Iso H, Date C, Kikuchi S, Tamakoshi A. Dietary folate and vitamin b6 and B12 intake in relation to mortality from cardiovascular diseases: Japan Collaborative Cohort Study. Stroke 2010;41(6):1285‐9. [PUBMED: 20395608]

Deshmukh 2010 {published data only}

Deshmukh US, Joglekar CV, Lubree HG, Ramdas LV, Bhat DS, Naik SS, et al. Effect of physiological doses of oral vitamin B12 on plasma homocysteine: a randomized, placebo‐controlled, double‐blind trial in India. European Journal of Clinical Nutrition 2010;64(5):495‐502. [PUBMED: 20216560]

Durga 2011 {published data only}

Durga J, Bots ML, Schouten EG, Grobbee DE, Kok FJ, Verhoef P. Effect of 3 y of folic acid supplementation on the progression of carotid intima‐media thickness and carotid arterial stiffness in older adults. American Journal of Clinical Nutrition 2011;93(5):941‐9. [PUBMED: 21430116]

Earnest 2012 {published data only}

Earnest CP, Kupper JS, Thompson AM, Guo W, Church T. Complementary effects of multivitamin and omega‐3 fatty acid supplementation on indices of cardiovascular health in individuals with elevated homocysteine. International Journal for Vitamin and Nutrition Research 2012;82(1):41‐52. [PUBMED: 22811376]

Ebbing 2009 {published data only}

Ebbing M, Bonaa KH, Nordrehaug JE, Ueland PM, Arnesen E, Refsum H, et al. Combined results and long‐term follow‐up in NORVIT and WENBIT with 6837 coronary artery disease patients: homocysteine‐lowering B‐vitamin treatment does not prevent major cardiovascular events. Journal of Internal Medicine 2009;30(4):184. [PUBMED: 20698927]

Ebbing 2009a {published data only}

Ebbing M, Bonaa KH, Nygard O, Arnesen E, Ueland PM, Nordrehaug JE, et al. Cancer incidence and mortality after treatment with folic acid and vitamin B12. JAMA 2009;302(19):2119‐26. [PUBMED: 19920236]

FINEST 2006 {published data only (unpublished sought but not used)}

Nevado J. Folate intervention in non‐ST elevation myocardial infarction and unstable angina: a randomised placebo‐controlled trial [2006]. http://controlled‐trials.com/ISRCTN30249553/homocysteine (accessed 12 October 2007).

Green 2010 {published data only}

Green TJ, Skeaff CM, McMahon JA, Venn BJ, Williams SM, Devlin AM, et al. Homocysteine‐lowering vitamins do not lower plasma S‐adenosylhomocysteine in older people with elevated homocysteine concentrations. British Journal of Nutrition 2010;103(11):1629‐34. [PUBMED: 20089204]

Holmes 2011 {published data only}

Holmes MV, Newcombe P, Hubacek JA, Sofat R, Ricketts SL, Cooper J, et al. Effect modification by population dietary folate on the association between MTHFR genotype, homocysteine, and stroke risk: a meta‐analysis of genetic studies and randomised trials. Lancet 2011;378(9791):584‐94. [PUBMED: 21803414]

Huang 2012 {published data only}

Huang T, Chen Y, Yang B, Yang J, Wahlqvist ML, Li D. Meta‐analysis of B vitamin supplementation on plasma homocysteine, cardiovascular and all‐cause mortality. Clinical Nutrition 2012;31(4):448‐54. [PUBMED: 22652362]
Huang T, Li D. Reply to Fang SK‐‐Meta‐analysis of B vitamin supplementation on plasma homocysteine, cardiovascular and all‐cause mortality. Clinical Nutrition 2013;32(2):315‐6. [PUBMED: 23391457]
Zhou C, Wu J, Fang S. Meta‐analysis of B vitamin supplementation on plasma homocysteine, cardiovascular and all‐cause mortality. Clinical Nutrition 2013;32(2):314. [PUBMED: 23433911]

Huo 2012 {published data only}

Huo Y, Qin X, Wang J, Sun N, Zeng Q, Xu X, et al. Efficacy of folic acid supplementation in stroke prevention: new insight from a meta‐analysis. International Journal of Clinical Practice 2012;66(6):544‐51. [PUBMED: 22607506]

Imasa 2009 {published data only}

Imasa MS, Gomez NT, Nevado JB. Folic acid‐based intervention in non‐ST elevation acute coronary syndromes. Asian Cardiovascular & Thoracic Annals 2009;17(1):13‐21. [PUBMED: 19515873]

Jardine 2012 {published data only}

Jardine MJ, Kang A, Zoungas S, Navaneethan SD, Ninomiya T, Nigwekar SU, et al. The effect of folic acid based homocysteine lowering on cardiovascular events in people with kidney disease: systematic review and meta‐analysis. BMJ 2012;344:e3533. [PUBMED: 22695899]

Ji 2013 {published data only}

Ji Y, Tan S, Xu Y, Chandra A, Shi C, Song B, et al. Vitamin B supplementation, homocysteine levels, and the risk of cerebrovascular disease: a meta‐analysis. Neurology 2013;81(15):1298‐307. [PUBMED: 24049135]

Lange 2004 {published data only}

Lange H, Suryapranata H, De Luca G, Börner C, Dille J, Kallmayer K, et al. Folate therapy and in‐stent restenosis after coronary stenting. New England Journal of Medicine 2004;350:2673‐81. [PUBMED: 15215483]

Lee 2010 {published data only}

Lee M, Hong KS, Chang SC, Saver JL. Efficacy of homocysteine lowering therapy with folic acid in stroke prevention: a meta‐analysis of randomized controlled trials. Stroke. 2010; Vol. 41:e291. [ISSN: 0039‐2499]
Lee M, Hong KS, Chang SC, Saver JL. Efficacy of homocysteine‐lowering therapy with folic acid in stroke prevention: a meta‐analysis. Stroke 2010;41(6):1205‐12. [PUBMED: 20413740]

Lonn 2007 {published data only}

Lonn E. Homocysteine in the prevention of ischemic heart disease, stroke and venous thromboembolism: therapeutic target or just another distraction?. Current Opinion in Hematology 2007;14(5):481‐7. [PUBMED: 17934354]

Mager 2009 {published data only}

Mager A, Orvin K, Koren‐Morag N, Lev IE, Assali A, Kornowski R, et al. Impact of homocysteine‐lowering vitamin therapy on long‐term outcome of patients with coronary artery disease. American Journal of Cardiology 2009;104(6):745‐9. [PUBMED: 19733705]

Manolescu 2010 {published data only}

Manolescu BN, Oprea E, Farcasanu IC, Berteanu M, Cercasov C. Homocysteine and vitamin therapy in stroke prevention and treatment: a review. Acta Biochimica Polonica 2010;57(4):467‐77. [PUBMED: 21140003]

Mei 2010 {published data only}

Mei W, Rong Y, Jinming L, Yongjun L, Hui Z. Effect of homocysteine interventions on risk of cardiocerebrovascular events: a meta‐analysis of randomized controlled trials. Circulation 2010;122(2):e140‐1.
Mei W, Rong Y, Jinming L, Yongjun L, Hui Z. Effect of homocysteine interventions on the risk of cardiocerebrovascular events: a meta‐analysis of randomised controlled trials. International Journal of Clinical Practice 2010;64(2):208‐15. [PUBMED: 19912385]

Méndez‐González 2010 {published data only}

Mendez‐González J, Rodríguez‐Millán E, Julve J, Blanco‐Vaca F. Vitamin treatments that lower homocysteine concentration: can they decrease cerebrovascular disease in primary prevention? [Tratamientos vitamínicos para disminuir la concentración de homocisteína: reducen el riesgo de enfermedad cerebrovascular en prevención primaria?]. Revista de Neurologia 2010;50(4):235‐44. [PUBMED: 20198596]

Miller 2010 {published data only}

Miller ER, Juraschek S, Pastor‐Barriuso R, Bazzano LA, Appel LJ, Guallar E. Meta‐analysis of folic acid supplementation trials on risk of cardiovascular disease and risk interaction with baseline homocysteine levels. American Journal of Cardiology 2010;106:517‐27. [PUBMED: 20691310]

Moghaddasi 2010 {published data only}

Moghaddasi M, Mamarabad M. Homocysteine, vitamin B12 and folic acid levels in cerebrovascular accident: a case‐control study. Journal of Neurology 2009;256(Suppl 2):S171.
Moghaddasi M, Mamarabadi M, Mirzadeh S, Freydoonnejad AA, Razjouyan H. Homocysteine, vitamin B12 and folate levels in Iranian patients with ischemic stroke. Neurological Research 2010;32(9):953‐6. [PUBMED: 20433777]

Ntaios 2009 {published data only}

Ntaios G, Savopoulos C, Grekas D, Hatzitolios A. The controversial role of B‐vitamins in cardiovascular risk: an update. Archives of Cardiovascular Diseases 2009;102(12):847‐54. [PUBMED: 19963194]

Ntaios 2010 {published data only}

Ntaios G, Savopoulos C, Karamitsos D, Economou I, Destanis E, Chryssogonidis I, et al. The effect of folic acid supplementation on carotid intima‐media thickness in patients with cardiovascular risk: a randomized, placebo‐controlled trial. International Journal of Cardiology 2010;143(1):16‐9. [PUBMED: 19201496]

PACIFIC 2002 {published data only}

Neal B, MacMahon S, Ohkubo T, Tonkin A, Wilcken D, PACIFIC Study Group. Dose‐dependent effects of folic acid on plasma homocysteine in a randomized trial conducted among 723 individuals with coronary heart disease. European Heart Journal 2002;23:1509‐15. [MEDLINE: 12395803]

Pan 2012 {published data only}

Pan Y, Guo LL, Cai LL, Zhu XJ, Shu JL, Liu XL, et al. Homocysteine‐lowering therapy does not lead to reduction in cardiovascular outcomes in chronic kidney disease patients: a meta‐analysis of randomised, controlled trials. British Journal of Nutrition 2012;108(3):400‐7. [PUBMED: 22244447]

Rautiainen 2010 {published data only}

Rautiainen S, Akesson A, Levitan EB, Morgenstern R, Mittleman MA, Wolk A. Multivitamin use and the risk of myocardial infarction: a population‐based cohort of Swedish women. American Journal of Clinical Nutrition 2010;92(5):1251‐6. [PUBMED: 20861174]

Sharifi 2010 {published data only}

Sharifi F, Fakhrzadeh H, Mirarefin M, Pourebrahim R, Nouri M, Forouzanfar MH, et al. The effects of high‐dose folic acid on blood pressure of hypertensive adults with hyperhomocysteinemia: a randomized double‐blind placebo controlled clinical trial (Tehran homocysteine survey). Iranian Journal of Diabetes and Lipid Disorders 2010;9:13‐20.

Shidfar 2009 {published data only}

Shidfar F, Homayounfar R, Fereshtehnejad SM, Kalani A. Effect of folate supplementation on serum homocysteine and plasma total antioxidant capacity in hypercholesterolemic adults under lovastatin treatment: a double‐blind randomized controlled clinical trial. Archives of Medical Research 2009;40(5):380‐6. [PUBMED: 19766902]

Sudchada 2012 {published data only}

Sudchada P, Saokaew S, Sridetch S, Incampa S, Jaiyen S, Khaithong W. Effect of folic acid supplementation on plasma total homocysteine levels and glycemic control in patients with type 2 diabetes: a systematic review and meta‐analysis. Diabetes Research and Clinical Practice 2012;98(1):151‐8. [PUBMED: 22727498]

Swiss 2002 {published data only}

Schnyder G, Roffi M, Flammer Y, Pin R, Hess OM. Effect of homocysteine‐lowering therapy with folic acid, vitamin B12, and vitamin B6 on clinical outcome after percutaneous coronary intervention: the Swiss Heart study: a randomized controlled trial. JAMA 2002;288:973‐9. [PUBMED: 12190367]

Tighe 2011 {published data only}

Tighe P, Ward M, McNulty H, Finnegan O, Dunne A, Strain J, et al. A dose‐finding trial of the effect of long‐term folic acid intervention: implications for food fortification policy. American Journal of Clinical Nutrition 2011;93(1):11‐8. [PUBMED: 20980493]

Vesin 2007 {published data only}

Vesin C, Mairesse S, Iaria P, Blacher J. Efficacy of folic acid in prevention of cerebrovascular disease [Efficacite de l’acide folique dans la prevention cerebrovasculaire]. Medecinedes Maladies Metaboliques 2007;1:50‐2. [EMBASE: 2007490543]

Wang 2007 {published data only}

Wang X, Qin X, Demirtas H, Li J, Mao G, Huo Y, et al. Efficacy of folic acid supplementation in stroke prevention: a meta‐analysis. Lancet 2007;369:876‐82. [PUBMED: 17544768]

Wang 2012 {published data only}

Wang ZM, Zhou B, Nie ZL, Gao W, Wang YS, Zhao H, et al. Folate and risk of coronary heart disease: a meta‐analysis of prospective studies. Nutrition, Metabolism, and Cardiovascular Diseases 2012;22(10):890‐9. [PUBMED: 21924595]

Wierzbicki 2007 {published data only}

Wierzbicki AS. Homocysteine and cardiovascular disease: a review of the evidence. Diabetes & Vascular Disease Research 2007;4(2):143‐50. [PUBMED: 17654449]

Yang 2012 {published data only}

Yang HT, Lee M, Hong KS, Ovbiagele B, Saver JL. Efficacy of folic acid supplementation in cardiovascular disease prevention: an updated meta‐analysis of randomized controlled trials. European Journal of Internal Medicine 2012;23(8):745‐54. [PUBMED: 22884409]

Zappacosta 2013 {published data only}

Zappacosta B, Mastroiacovo P, Persichilli S, Pounis G, Ruggeri S, Minucci A, et al. Homocysteine lowering by folate‐rich diet or pharmacological supplementations in subjects with moderate hyperhomocysteinemia. Nutrients 2013;5(5):1531‐43. [PUBMED: 23698160]

Zhang 2009 {published data only}

Zhang C, Zhu HL. Effect of B vitamins supplementation on cardiovascular and cerebrovascular disease by lowering plasma homocysteine concentration: a meta‐analysis [Chinese]. Chinese Journal of Evidence‐Based Medicine 2009;1:55‐62. [ISSN: 1672‐2531]

Zhang 2013 {published data only}

Zhang C, Chi FL, Xie TH, Zhou YH. Effect of B‐vitamin supplementation on stroke: a meta‐analysis of randomized controlled trials. PloS One 2013;8(11):e81577. [PUBMED: 24282609]

Zhou 2011 {published data only}

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Characteristics of studies

Characteristics of included studies [ordered by study ID]

Jump to:

BVAIT 2009

Methods

Multicentre study: yes
Country: USA

Intention‐to‐treat: yes (an intention‐to‐treat analysis was performed for all participants who had carotid ultrasonography at baseline and at least 1 follow‐up visit, page 731)

Unit of randomisation: patients

Follow‐up period (years): B vitamins group (3.14 (0.48 to 4.56) versus placebo group (3.07 (0.46 to 5.0))

Participants

Eligibility: 5309

Randomised: 506 (254 vitamins versus 252 placebo)

  • Age (years)

Overall: 61.4
B vitamins group: 61.7 (± 10.1)

Placebo group: 61.1 (± 9.6)

  • Gender (men):

Overall: 61%
B vitamins group: 61%

Placebo group: 61%

  • Inclusion criteria:

  1. Men and postmenopausal women 40 years old

  2. Fasting tHcy 8.5 mol/L

  3. No clinical signs/symptoms of cardiovascular disease (CVD)

  • Exclusion criteria:

  1. Fasting triglycerides > 5.64 mmol/L (500 mg/dL)

  2. Diabetes mellitus or fasting serum glucose > 6.99 mmol/L (126 mg/dL)

  3. Systolic blood pressure ≥ 160 mm Hg and/or diastolic blood pressure ≥ 100 mm Hg

  4. Untreated thyroid disease

  5. Creatinine clearance < 70 mL/min

  6. Life‐threatening illness with prognosis 5 years

  7. 5 alcoholic drinks daily

Interventions

  • HLI‐intervention: folic acid (5 mg), vitamin B12 (0.4 mg) and vitamin B6 (50 mg, daily supplementation)

  • Control: placebo

  • Treatment duration: initial 2.5‐year treatment period was extended on average 1 to 2 years

Outcomes

  • Primary:

Rate of change in the right distal carotid artery intima media thickness

  • Secondary:

Changes in calcium in the coronary arteries and abdominal aorta

  • Safety:

  1. Deaths

  2. Cardiovascular events

  3. Cerebrovascular events

  4. Arterial revascularisation procedures

  5. Cancers

  6. Occurrence of white blood cell count below the laboratory normal limit (4000 cells/μL)

Notes

  • Identifier: NCT00114400

  • Conducted between 6 November 2000 and 1 June 2006

  • A priori sample estimation: yes

  1. Quote: "Sample size based on carotid artery intima media thickness progression required 176 subjects/arm to detect a moderate effect size of 0.30 at 0.05 significance (2‐sided) with 0.80 power. A total of 506 subjects were recruited to accommodate anticipated dropouts and initiation of lipid‐lowering medications on‐trial." (page 731)

  • Financial disclosures: not reported

  • Other disclosures: none

  • Funding/support: Grant R01AG‐17160 from the National Institute on Aging, National Institutes of Health. Leiner Health Products provided the B vitamin supplements and placebo

We sent an email to the main author of this trial in order to get the type cardiovascular event data by comparison group (4 March 2012)

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Quote: "Computer‐generated random numbers were used to assign participants" (page 731)

Allocation concealment (selection bias)

Low risk

Quote: "Computer‐generated random numbers were used to assign participants" (page 731)

Blinding of participants and personnel (performance bias)
All outcomes

Low risk

Quote: "Participants, clinical staff, imaging specialists, and data monitors were masked to treatment assignment." (page 731)

Blinding of outcome assessment (detection bias)
All outcomes

Low risk

Quote: "...imaging specialists, ... were masked to treatment assignment." (page 731). & "Scans were analyzed without knowledge of treatment assignment using validated calcium scoring software" (for secondary outcome)" (page 731)

Comments: the main outcomes were to assess the impact of the HLI on reduction of subclinical atherosclerosis progression

Incomplete outcome data (attrition bias)
All outcomes

Low risk

  • B vitamins group

  1. Lost to follow‐up (n = 27): brain tumour (n = 1), medical problems (n = 2), refused methionine test (n = 1), active military duty (n = 1), too busy (n = 22)

  2. Discontinued intervention (n = 8): attributed intervention to a medical problem (n = 1), medical problem (n = 2), wanted to take vitamins (n = 1), too busy (n = 4)

  • Placebo group

  1. Lost to follow‐up (n = 27): died (n = 2), medical problems (n = 4), refused methionine test (n = 1), active military duty (n = 1), too busy (n = 19)

  2. Discontinued Intervention (n = 7): attributed intervention to a medical problem (n = 1), medical problem (n = 3), wanted to take vitamins (n = 2), too busy (n = 1)

  • Evaluable included in analysis:

  1. B vitamins group: 97.6% (248/254)

  2. Placebo group: 96% (242/252)

  • Completed the initially planned (2.5‐year trial period): 8.1% (446/506): (88% (223/446) B vitamin; 88% (223/446) placebo)

Selective reporting (reporting bias)

Low risk

The study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified. We also checked www.clinicaltrials.gov and the ID number was: NCT00114400

Other bias

Low risk

CHAOS 2002

Methods

Multicentre study
Follow‐up period: mean of 1.7 years

Participants

1882 patients randomised (folic acid: 942 versus placebo: 940 patients)

  • Gender: not reported

  • Age: not reported

  • Homocysteine levels at baseline (treatment group) (μmol/L): 11.2 ± 6.9 μmol/L

  • Inclusion criteria (1 of the following):

  1. Positive coronary angiogram

  2. Admission with MI or unstable angina

  • Exclusion criteria: not reported

Interventions

  • Intervention: folic acid 5 mg per day

  • Control: placebo in addition to usual drugs

Treatment duration: 2 years

Outcomes

Composite outcome: MI, revascularisation, death from cardiovascular cause

Notes

  • Sponsors: not available

  • Other: data not yet fully published. Results in the table correspond to conference proceedings

Homocysteine levels were only collected in 2 participating centres

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Unclear risk

Described as randomised

Insufficient information about the sequence generation process to permit judgement of 'Low risk' or 'High risk' Data not yet fully published. Results in the table correspond to conference proceedings

Allocation concealment (selection bias)

Unclear risk

Insufficient information about the sequence generation process to permit judgement of 'Low risk' or 'High risk' Data not yet fully published. Results in the table correspond to conference proceedings

Blinding of participants and personnel (performance bias)
All outcomes

Unclear risk

Described as double‐blinded. However, the information was obtained from the final report (abstract)

Insufficient information to permit judgement of 'Low risk' or 'High risk'

Blinding of outcome assessment (detection bias)
All outcomes

Unclear risk

Described as double‐blinded. However, the information was obtained from the final report (abstract)

Insufficient information to permit judgement of 'Low risk' or 'High risk'

Incomplete outcome data (attrition bias)
All outcomes

Unclear risk

Flow of participants during trial was not reported. Data not yet fully published. Results in the table correspond to conference proceedings

Selective reporting (reporting bias)

Low risk

The study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified

Other bias

Unclear risk

Insufficient information to assess whether an important risk of bias exists

FOLARDA 2004

Methods

Multicentre study

Country: The Netherlands
Follow‐up period: 1 year

Participants

283 randomised patients (folic acid: 140 versus standard care: 143)

  • Gender (% men): folic acid: 69% versus standard care: 70%

  • Age (mean): folic acid: 59 years versus standard care: 59

  • Homocysteine levels at baseline: not reported

  • Inclusion criteria (1 of the following):

  1. Myocardial infarction

  2. Total cholesterol value at admission or within 24 hours after onset of symptoms: > 6.5 μmol/L (251 mg/dL)

  3. Elevation of CK‐MB at least 2 times upper the limit of normal function

  4. Markedly increased chest pain lasting more than 30 minutes or classical ECG changes

  • Exclusion criteria:

  1. Age under 18 years,

  2. Use of lipid‐lowering agents within the previous 3 months

  3. High triglyceride levels > 4.5 μmol/L

  4. Known familial dyslipidaemia

  5. Low vitamin B12 levels

  6. Hyperhomocysteinaemia (total plasma homocysteine > 18 μmol/L) or a known disturbed methionine loading test (total plasma homocysteine > 47 μmol/L)

  7. Severe renal failure (serum creatinine > 180 μmol/L)

  8. Hepatic disease

  9. Severe heart failure (New York Heart Association class IV)

  10. Scheduled percutaneous coronary intervention or coronary artery bypass graft operation

Interventions

  • Intervention:

Folic acid: 5 mg per day
Treatment was initiated at least 1 day prior to hospital discharge, and no later of 14 days after the MI. The treatment continued for 1 year. Patients in this group also received statin therapy (fluvastatin, 40 mg per day). The clinician had at their discretion the prescription of additional prophylactic medication (aspirin, beta‐blocking agents and/or ACE inhibitors)

  • Control:

Standard care: statin therapy (fluvastatin, 40 mg per day). The clinician had at their discretion the prescription of additional prophylactic medication (aspirin, beta‐blocking agents and/or ACE inhibitors)

  • Treatment duration: 1 year

Outcomes

  1. Cardiovascular death (sudden death, fatal recurrent MI, fatal stroke and other cardiovascular deaths)

  2. Non‐cardiovascular death

  3. Recurrent MI

  4. Recurrent ischaemia requiring hospitalisation or revascularisation

Notes

Study phase: III

  • A priori sample estimation: sample size calculation to detect (80% power and 5% significance level) a 50% reduction in clinical events in that kind of patients, assuming a 1‐year event rate of 30%. These numbers resulted in an estimation of 120 patients per group. Analyses conducted on ITT basis

  • Sponsors: AstraZeneca, The Netherlands, Working Group on Cardiovascular research, The Netherlands. One author is an Established Investigator of the Netherlands Heart Foundation

  • Other: author did not perform homocysteine‐level measures during the study

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Unclear risk

Quote: "patients were randomised..."

Insufficient information about the sequence generation process to permit judgement of 'Low risk' or 'High risk'

Allocation concealment (selection bias)

Unclear risk

Insufficient information to permit judgement of 'Low risk' or 'High risk'

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Quote: "... treatment with open label folic acid [...] or not"

Blinding of outcome assessment (detection bias)
All outcomes

Low risk

Quote: "An Independent Data and Safety Monitoring Committee adjudicated all major clinical events."

Incomplete outcome data (attrition bias)
All outcomes

High risk

23 patients discontinued treatment and no information is given

Selective reporting (reporting bias)

Low risk

The study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified

Other bias

Unclear risk

Insufficient information to permit judgement of 'Low risk' or 'High risk'

GOES 2003

Methods

Single‐centre study

Country: The Netherlands
Follow‐up period: 1 year

Participants

593 randomised patients (folic acid: 300 versus standard care: 293)

  • Gender (% men): folic acid: 76% versus standard care: 80%

  • Age (mean ± SD): folic acid: 64.9 ± 9.9 versus standard care: 65.5 ± 9.7

  • Homocysteine levels at baseline: not reported

  • Inclusion criteria:

  1. Myocardial infarction

  2. Coronary artery lesions (> 60%) on coronary angiography

  3. Percutaneous coronary intervention

  4. Coronary artery bypass graft surgery

  5. Patients had to be stable, with no invasive vascular procedures scheduled

  6. Statin therapy for at least 3 months

  7. Taking any form of vitamin B‐containing medication, regularly or sporadically

  • Exclusion criteria:

  1. Age < 18 years

  2. History of low vitamin B12 levels

  3. Therapy for hyperhomocysteinaemia

  4. Severe renal failure, or any other treatment for renal disease

  5. Hepatic disease

  6. Severe heart failure (New York Heart Association functional class IV)

  7. Serious illness that would exclude follow‐up time of at least 3 years

Interventions

  • Intervention: folic acid: 0.5 mg per day

  • Control group: standard care

  • Intensive follow‐up and treatment of risk factors, with counselling provided by a qualified nurse. Statin dosage was increased when necessary. Dietary counselling was provided and smoking discouraged

  • Treatment duration: not reported

Outcomes

  • Primary (composite):

  1. Composite: vascular death (sudden death, fatal recurrent MI, fatal stroke and other cardiovascular deaths)

  2. Non‐cardiovascular death

  3. Recurrent acute coronary syndromes

  4. Invasive coronary procedures

  5. Cerebrovascular accident or transient ischaemic attack

  6. Any other vascular surgery (carotid endarterectomy, abdominal aneurysmectomy, or peripheral vascular surgery including limb amputation for vascular reasons)

  • Secondary:

  1. Hospitalisation for unstable angina

Notes

  • Study phase: III

  • A priori sample size estimation: (80% power and 5% significance level) to detect a 50% reduction in clinical events in that type of patients, assuming a 2‐year event rate of 15%. These numbers resulted in an estimation of 300 patients per group. Analyses conducted on ITT basis

  • Sponsors: trial with public funding (Stichting Paracard)

  • Other: the trial allowed the entry of patients taking vitamin B supplementation. These patients showed higher levels of serum folate and lower levels of homocysteine

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Quote: "A computer program randomly allocated patients [...] to treatment"

Allocation concealment (selection bias)

Unclear risk

No information reported about this domain

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Quote: "... treatment with open label folic acid [...] or standard care."

Blinding of outcome assessment (detection bias)
All outcomes

Low risk

Quote: "Adjudication of all clinical events was performed by an independent end point monitoring committee unaware of treatment arm."

Incomplete outcome data (attrition bias)
All outcomes

Low risk

After randomisation, 12 patients per group withdrew from the study but were followed up and included in the final analysis

Selective reporting (reporting bias)

Low risk

The study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified

Other bias

Unclear risk

Insufficient information to permit judgement of 'Low risk' or 'High risk'

HOPE‐2 2006

Methods

Multicentre international study (13 countries; 145 centres)
Follow‐up period: 5 years

Participants

5522 patients randomised (vitamin: 2758 versus placebo group: 2764 patients)

  • Gender (% men): vitamin: 71.1% versus placebo: 72.4%

  • Age (mean ± SD): vitamin: 68.8 ± 7.1 versus placebo: 68.9 ± 6.8

  • Homocysteine level at baseline: 12.2 μmol/L (1.6 mg/L)

  • Inclusion criteria:

  1. Men and women aged > 55 years

  2. History of vascular disease (coronary, cerebrovascular or peripheral vascular) or diabetes and additional risk factors for atherosclerosis, irrespective of their homocysteine levels, from countries with mandatory folate fortification of food (Canada and the United States) and countries without mandatory folate fortification (Brazil, western Europe and Slovakia)

  • Exclusion criteria:

  1. Patients taking vitamin supplements containing more than 0.2 mg of folic acid per day

Interventions

Intervention:

  • Multivitamin therapy with 2.5 mg of folic acid, 50 mg of vitamin B6 and 1 mg of vitamin B12 per day

Control:

  • Matching placebo daily

Treatment duration: 5 years

Outcomes

Primary outcome (composite):

  • Death from cardiovascular causes, myocardial infarction, stroke

  • Secondary outcomes:

  • Total ischaemic events (composite of death from cardiovascular causes, myocardial infarction, stroke, hospitalisation for unstable angina and revascularisation)

  • Death from any cause

  • Hospitalisation for unstable angina or congestive heart failure

  • Revascularisation

  • Incidence and death for cancer

  • Other outcomes: transient ischaemic attacks, venous thromboembolic events, fractures

Notes

  • Study phase: III, registered (ClinicalTrials.gov number NCT00106886)

  • Sample calculation a priori: yes. Sample size calculation to detect between a 17% and a 20% reduction (80% and 90% power, respectively) in the risk rate of the primary endpoint over 5 years of follow‐up (assuming an annual event rate of 4% in the placebo group). These numbers resulted in an estimation of 5000 patients. Analyses conducted on ITT basis

  • Sponsors: public funding (Canadian Institutes of Health Research). The study medication was provide by Jamieson Laboratories. They were not involved in the design, execution, analysis or reporting of the trial results

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Quote: "The study used central telephone randomization"

Allocation concealment (selection bias)

Low risk

Centralised telephone randomisation (accessible 24 hours a day)

Blinding of participants and personnel (performance bias)
All outcomes

Low risk

Quote: "All study investigators, personnel, and participants were unaware of the randomization procedure and the treatment assignments."

Vitamins manufactured to be indistinguishable in colour, weight or ability to be dissolved in water

Blinding of outcome assessment (detection bias)
All outcomes

Low risk

This trial assessed objective outcomes

Incomplete outcome data (attrition bias)
All outcomes

Low risk

21 patients in the treatment group and 16 in the placebo group did not complete the study
Vital status known for 99.3% of the sample

Selective reporting (reporting bias)

Low risk

The study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified

Other bias

Low risk

NORVIT 2006

Methods

Multicentre study

Country: Norway

Follow‐up period: 3.5 years

Participants

3749 patients randomised (folic acid, vitamins B6 and B12: 937 versus folic acid, vitamin B12: 935 versus vitamin B6: 934 versus placebo: 943)

  • Gender (% men):

Folic acid, vitamins B6 and B12: 73%
Folic acid, vitamin B12: 74%
Vitamin B6: 73%
Placebo: 75%

  • Age (mean ± SD, years)

Folic acid, vitamins B6 and B12: 63.6 ± 11.9
Folic acid, vitamin B12: 63.2 ± 11.6
Vitamin B6: 62.5 ± 11.7
Placebo: 62.6 ± 11.4 years

  • Inclusion criteria:

  1. Men and women aged 30 to 85 years,

  2. History of acute MI within 7 days before randomisation

  • Exclusion criteria:

  1. Coexisting disease associated with a life expectancy < 4 years

  2. Prescribed treatment with B vitamins or untreated vitamin B deficiency

  3. Inability to follow the protocol, as judged by the investigator

Interventions

  • Intervention:

  1. Folic acid (group 1): 0.8 mg; vitamin B12: 0.4 mg; vitamin B6: 40 mg per day

  2. Folic acid (group 2): 0.8 mg; vitamin B12: 0.4 mg per day

  3. Vitamin B6 (group 3): 40 mg per day

  • Control: placebo

Medication was delivered in single capsules taken once per day. For the first 2 weeks after study entry patients in groups 1 and 2 received an additional folic acid dose (5 mg) per day, whereas the other 2 groups received placebo

Treatment duration: not clearly described

Outcomes

  • Primary outcome (composite):

  1. Recurrent MI, stroke and sudden death attributed to coronary artery disease

  • Secondary outcomes:

  1. Myocardial infarction

  2. Unstable angina pectoris requiring hospitalisation

  3. Coronary revascularisation with percutaneous coronary intervention or coronary artery bypass grafting

  4. Stroke

  5. Death from any cause

Incident cases of cancer

Notes

  • Study phase: III, registered (ClinicalTrials.gov number NCT00266487)

  • A priori sample size estimation: yes. Sample size calculation to detect a 20% relative reduction in the rate of primary endpoint (assuming 25% of endpoints in the placebo group). These numbers resulted in an estimation of 3500 patients assuming 750 primary events

The calculation of the sample size was based on data from previous Scandinavian trials, assuming the 3‐year rate of the primary endpoint would be 25% in the placebo group. The planned enrolment of 3500 patients, with an average follow‐up of 3.0 years, was expected to result in 750 primary events and give the study statistical power of more than 90% to detect a 20% relative reduction in the rate of the primary endpoint, given a 2‐sided alpha value of 0.05

  • Sponsors: public and governmental funding. Supported by the Norwegian Research Council, the Council on Health and Rehabilitation, the University of Tromso, the Norwegian Council on Cardiovascular Disease, the Northern Norway Regional Health Authority, the Norwegian Red Cross, the Foundation to Promote Research into Functional Vitamin B12 Deficiency and an unrestricted private donation. The study medication was provide by Alpharma. The sponsors had no role in the design, conduct or reporting of the study

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Unclear risk

No information reported about this domain

Allocation concealment (selection bias)

Low risk

The manufacturer provided centrally study sites with blocks of medication assigned in numerical order

Blinding of participants and personnel (performance bias)
All outcomes

Low risk

All study personnel and participants were unaware of the treatment assignments

Vitamins were manufactured to be indistinguishable in colour, weight or ability to be dissolved in water

Blinding of outcome assessment (detection bias)
All outcomes

Low risk

Quote: "All end points were adjudicated by members of the end‐points committee, who were unaware of patients’ treatment assignments."

Incomplete outcome data (attrition bias)
All outcomes

Low risk

11% of patients stopped the medication
94% attended the final visit, but data on mortality were available for the entire sample. Incomplete outcome data for 20 patients
Patients that had not completed the planned follow‐up were followed up by phone or consulted for vital status

Selective reporting (reporting bias)

Low risk

The study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified

Other bias

Low risk

SEARCH 2010

Methods

Multicentre study (88 sites)
Country: United Kingdom

Intention‐to‐treat: yes

Unit of randomisation: patients were survivors of MI

Follow‐up period: 6.7 ± 1.5 person‐years

Participants

Clinical condition: survivors of myocardial infarction in secondary care hospitals

  1. Potential participants invited by mail: 83,237

  2. Attended screening visit: 34,780

  3. Entered pre‐randomisation run‐in‐phase: 19,190. Quote: "Run‐in treatment involved placebo vitamin tablets (and 20 mg simvastatin daily, which allowed baseline lipid levels to be assessed after all participants had received the same statin therapy) (page 2487)

  4. Randomised: 12,064 (folic acid and B12: 6033 versus placebo: 6031)

  • Gender (% men)

Men: 10,012
Women: 2052

  1. Folic acid and B12: 83%

  2. Placebo: 83%

  • Age (at randomisation)

Mean (SD) age of 64.2 (8.9) years

Folic acid and vitamin B12:

  1. < 60 years: 31%

  2. ≥ 60 years to < 70 years: 40%

  3. ≥ 70 years: 29%

Placebo:

  1. < 60 years: 31%

  2. ≥ 60 years to < 70 years: 40%

  3. ≥ 70 years: 29%

  • Inclusion criteria:

  1. Men and women

  2. Aged 18 to 80 years

  3. History of myocardial infarction

  4. Had no clear indication for folic acid

  5. Blood cholesterol levels of at least 135 mg/dL if already taking a statin medication or 174 mg/dL if not (to convert cholesterol to mmol/L, multiply by 0.0259)

  • Exclusion criteria:

  1. Chronic liver, renal or muscle disease

  2. History of any cancer (except non‐melanoma skin cancer)

  3. Use of potentially interacting medications

Interventions

  • Intervention: 1 tablet daily containing 2 mg folic acid plus 1 mg vitamin B12

  • Control: placebo

Both medications were supplied in specially prepared calendar packs (and, separately, using a 2 x 2 factorial design, either 80 mg or 20 mg simvastatin daily)

Outcomes

  • Primary outcome (composite):

  1. Incidence of first major vascular event, defined as non‐fatal MI or death from coronary heart disease, fatal or non‐fatal stroke, or any arterial revascularisation

  • Secondary outcomes:

  1. Major vascular events in the first year after randomisation (when little difference was anticipated) and, separately, in the later years of the treatment period

  2. Major vascular events among participants subdivided into 3 similar‐sized groups with respect to blood homocysteine levels at the end of the pre‐randomisation run‐in period (before any study vitamin treatment had been taken)

  3. Major vascular events in the presence of one or other of the allocated study simvastatin regimens

  4. Major coronary events, defined as non‐fatal MI, death from coronary disease, or coronary revascularisation

  5. Any type of stroke (excluding transient ischaemic attacks)

  • Tertiary outcomes:

  1. Total and cause‐specific mortality (considering vascular and non‐vascular causes separately)

  2. Vascular mortality excluding the first year after randomisation

  3. Coronary and non‐coronary revascularisation separately

  4. Confirmed haemorrhagic and other strokes separately

  5. Pulmonary embolus

  6. Total and site‐specific cancers

  7. Hospitalisations for various other causes

  8. Adverse effects of treatment

Notes

  • Identifier: ISRCTN 74348595

  • Reason for a pre‐randomisation run‐in phase: to limit subsequent randomisation to those likely to take the randomly allocated study treatment for several years (page 2487)

  • Conducted between September 1998 and June 2008

  • A priori sample estimation: yes

  1. Quote: "It was prespecified in the protocol that the steering committee could modify the study plans while still blinded to the event rates in each treatment group." (page 2488)

  2. Quote: "in 2004, blind to interim results for clinical outcomes, the steering committee decided to change the primary outcome from major coronary events to major vascular events and to continue until at least 2800 patients had had a confirmed major vascular event in order to have 90% power at P.05 to detect a 10% reduction in risk." (page 2489)

  3. Comment: assumptions for sample size estimation were based on Boushey 1995; Bowman 2007; HSC 2002 and SSSS 1994

  • Financial disclosures: reported

  • Funding/support: Quote: "The study was funded by Merck (manufacturers of simvastatin and suppliers of the vitamins). The CTSU also receives core support from the UK Medical Research Council and the British Heart Foundation." (page 2493)

  • Role of sponsors: Quote: "The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, and approval of the manuscript. The University of Oxford acted as the sponsor of the study." (page 2493)

  • Additional information: http://www.searchinfo.org/SEARCH_protocol.pdf

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Quote: "The central telephone randomization system used a minimization algorithm to balance the treatment groups with respect to major prognostic factors." (page 2487)

Allocation concealment (selection bias)

Low risk

Quote: "The central telephone randomization system used a minimization algorithm to balance the treatment groups with respect to major prognostic factors." (page 2487)

Blinding of participants and personnel (performance bias)
All outcomes

Low risk

Quote: " All such information was reviewed by coordinating center clinicians who were unaware of the study treatment allocation and events coded according to prespecified criteria" (page 2487)

Blinding of outcome assessment (detection bias)
All outcomes

Low risk

No blinding of outcome assessment, but the review authors judge that the outcome measurement is not likely to be influenced by lack of blinding

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Vitamin group: 98.9% (5970/6033) completed follow‐up
Placebo group: 99.1% (5975/6031) completed follow‐up

Selective reporting (reporting bias)

Low risk

The study protocol is available and all of the study's pre‐specified (primary and secondary) outcomes that are of interest in the review have been reported in the pre‐specified way

Other bias

Low risk

SU.FOL.OM3 2010

Methods

Multicentre study (257 sites)
Country: France

Intention‐to‐treat: yes. "All analyses were conducted according to the principle of intention to treat" (page 2)

Unit of randomisation: patients with a history of ischaemic heart disease or stroke

Follow‐up period: median: 4.7 years; mean 4.2 ± 1.0 years

Participants

Clinical condition: patients with a history of ischaemic heart disease or stroke

  1. Patients assessed for eligibility: 3374

  2. Randomised: 2501 (B vitamins plus omega 3 fatty acids: 620, omega 3 fatty acids: 633, B vitamins: 622, and placebo: 626)

  3. Complete follow‐up: 2222 (89%)

  • Gender (% men)

Men: 1987
Women: 514

  1. B vitamins plus omega 3 fatty acids: 79.5%

  2. Omega 3 fatty acids: 79.2%

  3. B vitamins: 79.9%

  4. Placebo: 79.2%

  • Age

Mean (SD) age of 60.9 (8.8) years.

  1. B vitamins plus omega 3 fatty acids: 60.5 (53.9 to 68.9)

  2. Omega 3 fatty acids: 60.41 (5.7 to 68.7)

  3. B vitamins: 60.7 (54.7 to 68.3)

  4. Placebo: 60.9 (54.5 to 68.1)

  • Inclusion criteria:

  1. Men and women

  2. Aged 45 to 80 years

  3. History of acute coronary or cerebral ischaemic event within the 12 months before randomisation

  • Exclusion criteria:

  1. Age (< 45 years or > 80 years)

  2. Ill‐defined diagnosis of cardiovascular disease

  3. Inability or unwillingness to comply with study treatment

  4. Disease or treatment that might interfere with metabolism of homocysteine or omega 3 fatty acids, in particular methotrexate for treating cancer or rheumatoid arthritis and chronic renal failure (plasma creatinine concentration > 200 mol/L or creatinine clearance < 40 mL/min)

  5. Individuals with transient ischaemic attacks

Interventions

  • Intervention: 1 tablet daily containing 5‐methyltetrahydrofolate (560 μg), vitamin B6 (3 mg) and B12 (20 μg)

  • Control: placebo

Furthermore: supplement containing omega 3 polyunsaturated fatty acids (600 mg of eicosapentaenoic acid and docosahexaenoic acid at a ratio of 2:1)

Outcomes

  • Primary outcome (composite):

  1. First major cardiovascular event: non‐fatal myocardial infarction, ischaemic stroke or death from cardiovascular disease (including fatal myocardial infarction, stroke, sudden death (within 1 hour of onset of acute symptoms in the absence of violence or accident), aortic dissection, cardiac failure or other fatal event defined by the medical committee as having a cardiovascular cause)

  • Secondary outcomes:

  1. Acute coronary syndrome without myocardial infarction

  2. Resuscitation from sudden death

  3. Coronary artery bypass surgery

  4. Coronary angioplasty

  5. Cardiac failure

  6. Ventricular arrhythmia

  7. Supraventricular arrhythmia

  8. Cardiac surgery of any kind, transient ischaemic attack

  9. Deep vein thrombosis

  10. Pulmonary embolism

  11. Carotid surgery or carotid artery angioplasty

  12. Peripheral arterial surgery or angioplasty

  13. Any vascular procedure

  14. Death from all causes

Notes

  • Identifier: ISRCTN 41926726

  • Conducted between 1 February 2003 and 1 June 2007

  • A priori sample estimation: yes

  1. Quote: "The sample size was calculated for the estimated eventrate of 0.087 in the placebo group, based on the event rates observed in previous trials in similar populations and in epidemiological studies. No interaction between B vitamins and omega 3 fatty acids was anticipated. The planned enrolment of 2500 participants with an average follow‐up of five years was expected to have more than 90% power to detect a 10% reduction in the relative risk of major vascular events associated with B vitamins or omega 3 fatty acids and a 19% reduction for the combination of omega 3 fatty acids and B vitamins, given a two sided α value of 0.05." (page 3)

Comment: assumptions were based on Galan et al (HSC 2002; SU.FOL.OM3 2010; Yusuf 2000)

  • Competing interest: reported

  • Funding/support: Quote: "The SU.FOL.OM3 trial was supported by the French Ministry of Research (R02010JJ), Ministry of Health (DGS), Sodexo, Candia, Unilever, Danone, Roche Laboratory, Merck EPROVA GS, and Pierre Fabre Laboratory." (page 8)

  • The supplements were provided without charge by Merck Eprova AG (5‐methyltetrahydrofolate), Roche Laboratory (vitamins B6 and B12), and Pierre Fabre (omega 3 fatty acids). The gelatin capsules were manufactured by Catalent Pharma Solutions (Beinheim, France) (page 2)

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Quote: "Randomisation was performed by means of a computerised block sequence stratified by three age groups (44 – 54, 55 – 64, and 65 – 80 years), sex, prior disease at enrolment (myocardial infarction, acute coronary syndrome, or ischaemic stroke) and recruitment centre. Permuted block randomisation (with block size randomly selected as 8) was used." (page 2)

Allocation concealment (selection bias)

Low risk

Quote: "Randomisation was performed by means of a computerised block sequence stratified by three age groups (44 – 54, 55 – 64, and 65 – 80 years), sex, prior disease at enrolment (myocardial infarction, acute coronary syndrome, or ischaemic stroke) and recruitment centre. Permuted block randomisation (with block size randomly selected as 8) was used." (page 2)

Blinding of participants and personnel (performance bias)
All outcomes

Low risk

Quote: "Patients, clinicians, trial coordinators, and outcome investigators were blinded to treatment allocation." (page 2)
Quote: "treatment capsules for one year (and repeated yearly) in an appropriately labelled package." (page 2)

Blinding of outcome assessment (detection bias)
All outcomes

Low risk

Quote: "... and outcome investigators were blinded to treatment allocation." (page 2)

Quote: "All events were adjudicated by two independent committees of cardiologists or neurologists who were blinded to treatment allocation." (page 3)

Incomplete outcome data (attrition bias)
All outcomes

Low risk

  1. B vitamins plus omega 3 fatty acids: 11.8% (547/620)

  2. Omega 3 fatty acids: 9.6% (572/633)

  3. B vitamins: 12.6% (542/622)

  4. Placebo: 10.4% (561/626)

Comments: reasons for losses were reported

Selective reporting (reporting bias)

Low risk

The study protocol is available and all of the study's pre‐specified (primary and secondary) outcomes that are of interest in the review have reported in the pre‐specified way. "This study is registered with Current Controlled Trials (No ISRCTN41926726" (page 3)

Other bias

Low risk

VISP 2004

Methods

Country: USA, Canada and Scotland

Multicentre international study

Follow‐up period: 2 years

Participants

3680 randomised (high‐dose: 1827 versus low‐dose: 1853)

Gender (% men): high‐dose: 62.3% versus low‐dose: 62.8%

Age (mean ± SD): high‐dose: 66.4 (10.8) versus low‐dose: 66.2 (10.8)

  • Inclusion criteria:

  1. Non‐disabling ischaemic stroke (Modified Rankin Stroke Scale 3): onset 120 days before randomisation. Focal neurological deficit of likely atherothrombotic origin, classified as ischaemic stroke by questionnaire/algorithm or confirmed as new cerebral infarction consistent with symptoms by cranial computed tomography or brain magnetic resonance imaging

  2. Total homocysteine level 25th percentile for North American stroke population

  3. Age: ≥ 35 years

  4. Accessibility for follow‐up

  5. Agreement to take study medication and not take other multivitamins or pills containing folic acid or vitamin B6

  6. Written informed consent

  • Exclusion criteria:

  1. Potential sources of emboli (atrial fibrillation within 30 days of stroke, prosthetic cardiac valve, intracardiac thrombus or neoplasm, or valvular vegetation)

  2. Other major neurological illness that would obscure evaluation of recurrent stroke

  3. Life expectancy 2 years

  4. Renal failure requiring dialysis

  5. Untreated anaemia or untreated vitamin B12 deficiency

  6. Systolic blood pressure 185 mm Hg or diastolic blood pressure 105 mm Hg on 2 readings 5 minutes apart at time of eligibility determination

  7. Refractory depression, severe cognitive impairment, or alcoholism or other substance abuse

  8. Use within the last 30 days of medications that affect total homocysteine level (methotrexate, tamoxifen, levodopa, niacin or phenytoin) or bile acid sequestrants that can decrease folate levels

  9. Childbearing potential

  10. Participation in another trial with active intervention

  11. General anaesthesia or hospital stay of 3 days, any type of invasive cardiac instrumentation or endarterectomy, stent placement, thrombectomy or any other endovascular treatment of carotid artery within 30 days prior to randomisation or scheduled to be performed within 30 days after randomisation

Interventions

  • High‐dose multivitamin therapy

2.5 mg folic acid; 0.4 mg vitamin B12; 25 mg vitamin B6 per day

  • Low‐dose multivitamin therapy

20 micrograms folic acid; 6 micrograms vitamin B12; 200 micrograms vitamin B6 per day

  • Co‐interventions:

  1. Risk factor control education

  2. Aspirin (325 mg/d)

Duration of treatment: not described

Outcomes

  • Primary outcome:

  1. Recurrent cerebral infarction

  • Secondary outcomes:

  1. Coronary heart disease, including: myocardial infarction requiring hospitalisation; coronary revascularisation; and fatal coronary heart disease

  2. Death

Notes

  • Study phase: III

  • A priori sample size estimation: yes. Sample size calculation (80% power at 0.05 significance level for a 2‐sided test) to detect a 30% reduction in the rate of primary endpoint over 2 years of follow‐up (assuming 8% of events in the first year and 4% in the second year, with 20% losses to follow‐up). These numbers resulted in an estimation of 1800 patients per group. Trialists planned up to 6 interim analyses

  • Sponsors: supported by the National Institute of Neurological Disorders and Stroke (grant RO1 NS34447). The study medication was provided by Roche Inc. They had no role in the design and conduct of the study; the collection, analysis and interpretation of the data; or the preparation, review or approval of the manuscript

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Unclear risk

The allocation of participants was programmed by the statistical co‐ordinating centre, encrypted and entered into a data entry program installed on a study computer at each site

Allocation concealment (selection bias)

Low risk

Allocation programmed by the statistical co‐ordinating centre. All the information on assignment were encrypted an entered in computers in study sites
After verification of eligibility participants were assigned in 1 of 20 medication codes

Blinding of participants and personnel (performance bias)
All outcomes

Low risk

The drug distributor centre bottled and distributed the vitamins, which were manufactured to be indistinguishable in colour, weight or ability to be dissolved in water

Blinding of outcome assessment (detection bias)
All outcomes

Low risk

The primary endpoint was reviewed by a local neurologist and 2 external independent review neurologists

Incomplete outcome data (attrition bias)
All outcomes

Unclear risk

132 patients in the low‐dose group and 133 in the high‐dose group were lost to follow‐up. Of these 18 and 13 patients respectively had no contact after randomisation, and were not included in the analysis. 186 patients in the low‐dose group and 179 in the high‐dose group discontinued the assigned treatment

Patients who had not completed the planned follow‐up were invited to an exit visit

Selective reporting (reporting bias)

Low risk

The study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified

Other bias

Low risk

VITATOPS 2010

Methods

Multicentre study: 123 medical centres (20 countries) from 4 continents
Follow‐up period (median and interquartile range, years): 3.4 (2.0 to 5.5)
Intention‐to‐treat: yes

Unit of randomisation: patients with recent stroke or transient ischaemic attack within the past 7 months

Participants

8164 randomised
4089 received folic acid and vitamins B (B6 and B12)
4075 received placebo

  • Age (mean ± SD; years)

  1. Overall: 62.6 ± 12.5

  2. Vitamin: 62.5 ± 12.6

  3. Placebo:  62.6 ± 12.4

  • Gender (men):

  1. Overall: 64%

  2. Vitamin: 64% (2614/4089)

  3. Placebo: 64% (2604/4075)

  • Inclusion criteria:

  1. Stroke (ischaemic or haemorrhagic) or transient ischaemic attack (eye or brain), as defined by standard criteria, within the past 7 months

  2. Patients with haemorrhagic stroke

  • Exclusion criteria:

  1. Taking folic acid, vitamin B6, vitamin B12 or a folate antagonist (e.g. methotrexate)

  2. Pregnant or women of childbearing potential

  3. Patients with limited life expectancy (e.g. because of ill health)

Interventions

  • Intervention:

  1. Folic acid: 2 mg/d

  2. Vitamin B6: 25 mg/d

  3. Vitamin B12: 0.5 mg/d

  • Control: placebo

Co‐interventions: not reported

Outcomes

  • Primary outcome (composite): whichever occurred first

  1. Non‐fatal stroke

  2. Non‐fatal myocardial infarction

  3. Death from any vascular causes

  • Secondary outcomes:

  1. Stroke (non‐fatal or fatal)

  2. Myocardial infarction (non‐fatal or fatal)

  3. Death from any vascular cause

  4. Death from any cause

  5. Revascularisation procedures

  6. The composite of non‐fatal stroke, non‐fatal myocardial infarction and death from any vascular cause

  7. Revascularisation procedures of the coronary, cerebral or peripheral circulation

Notes

  • Identifier numbers: NCT00097669 and ISRCTN74743444

  • Date of study: 19 November 1998 to 31 December 2008

  • A priori sample size estimation: yes. Quote: "equally sized intervention and placebo groups, a minimum follow‐up of 6 months for the last patient to be randomly allocated, an annual primary outcome event rate of 8% in the placebo group, and a 15% decrease in the relative risk of the primary outcome among patients assigned to B vitamins (i.e., 6.8% per year) compared with placebo. For a type 1 error of 5% and type 2 error of 20%, and assuming a mean follow‐up of 2 years, a sample size of 3982 patients was required in each treatment group." (page 857). Comment: assumption for estimating annual primary outcome event rate in the placebo groups was based on CAPRIE 1996

  • Sponsor: Australia National Health and Medical Research Council, UK Medical Research Council, Singapore Biomedical Research Council, Singapore National Medical Research Council, Australia National Heart Foundation, Royal Perth Hospital Medical Research Foundation and Health Department of Western Australia

  • Rol of Sponsor: "The sponsors of the study had no role in study design, data collection, data analysis, data interpretation, the writing of the report, or in the decision to submit the paper for publication. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication." (page 858)

  • Conflicts of interest: reported

  • Vitamin tablets and matching placebo tablets were supplied by Blackmores, Australia (page 864)

  • All investigator‐reported outcomes and adverse events were audited by a masked adjudication committee (page 857)

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Quote: "Random allocation was done by use of a central 24 hrs telephone service or an interactive website by use of random permuted blocks stratified by hospital" (page 856)

Allocation concealment (selection bias)

Low risk

Quote: "Random allocation was done by use of a central 24 hrs telephone service or an interactive website by use of random permuted blocks stratified by hospital" (page 856)

Blinding of participants and personnel (performance bias)
All outcomes

Low risk

Quote: "Patients, clinicians, trial coordinators, and outcome investigators were masked to treatment allocation" (page 856)

Quote: "had the same colour and coating" (page 856)

Blinding of outcome assessment (detection bias)
All outcomes

Low risk

Quote: "...and outcome investigators were masked to treatment allocation" (page 856)

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Loss to final follow‐up:
Global: 8.6% (702/8164)
B vitamins group: 8.5% (348/4089)
Placebo group: 8.7% (354/4075)

Comment: reasons for losses were reported

Selective reporting (reporting bias)

Low risk

The study protocol is not available but it is clear that published reports include all expect outcomes, including those that were pre‐specified. This trial is registered with ClinicalTrials.gov, NCT00097669 and Current Controlled Trials, ISRCTN74743444." (page 858)

Other bias

Low risk

WAFACS 2008

Methods

Multicentre study

Country: USA
Follow‐up period: 7.3 years

Participants

N: 5442 randomised patients (vitamin group: 2721 patients; placebo group: 2721 patients)

  • Gender: women health professionals

  • Age (mean (SD)) years

Active group: 62.8 (8.8)
Control group: 62.8 (8.8)

  • Inclusion criteria

  1. Women

  2. Age: 40 years or older

  3. Postmenopausal or had no intention of becoming pregnant

  4. History of CVD or had at least 3 cardiac risk factors

  • Exclusion criteria:

  1. Cancer (excluding non‐melanoma skin cancer) within the past 10 years

  2. Serious non‐cardiovascular disease

  3. Warfarin or other anticoagulants use

Interventions

  • Intervention:

Folic acid: 2.5 mg; vitamin B12: 1 mg; vitamin B6: 50 mg per day

  • Control:

Matching placebo per day

  • Co‐interventions: vitamin C, vitamin E, ß‐carotene

  • Treatment duration: not clearly reported

Outcomes

  • Primary (composite):

  1. Incident myocardial infarction, stroke, coronary revascularisation procedures (coronary artery bypass grafting or percutaneous coronary intervention) and cardiovascular mortality

  • Secondary:

  1. Myocardial infarction rate

  2. Stroke rate

  3. Total coronary heart disease events (myocardial infarction, coronary revascularisation and death from coronary heart disease)

Notes

  • Study phase: III, registered (ClinicalTrials.gov number NCT00000541)

  • The information in this table was kindly supplied by Dr. Nancy Cook who was the statistician for the WACS and WAFACS studies (23 June 2008)

The WACS study was a 2 x 2 x 2 factorial trial of 3 antioxidants, vitamins C, E and beta‐carotene. Randomisation of the 8171 participants into the 8 treatment groups took place from June 1995 to October 1996, and was conducted using blocks of size 16 within 5‐year age groups. The folate/B6/B12 arm was added in April 1998, and the 5442 participants who were willing and eligible were randomised (at one time) using blocks of size 8 within strata defined by age and the other treatment arms. Participants were sent yearly supplies of calendar packs containing the study medications or matching placebo pills that were identical in appearance. All medical records were reviewed by an Endpoints Committee that was blinded to treatment assignment

  • A priori sample size estimation: sample size with 91.5% power to detect a 20% reduction in the primary endpoint (major vascular events). For the endpoints of total CHD (defined as non‐fatal MI, CHD death or revascularisation), MI and stroke, the minimum detectable risk reduction with 80% power ranges from 19% to 32%. A 2‐sided significance level of 0.05 was used

  • Sponsor: public funding and from several industry sources. Grant HL47959 from the National Heart, Lung, and Blood Institute of the National Institutes of Health. Vitamin E and its placebo were supplied by Cognis Corporation (La‐Grange, Illinois)

  • All other agents and their placebos were supplied by BASF Corporation (Mount Olive,New Jersey). Pill packaging was provided by Cognis and BASF. They did not participate in the design and conduct of the study; collection, management, analysis and interpretation of the data; and preparation, review or approval of the manuscript

  • Other: the analyses of the endpoints were done only for these confirmed outcomes. However, there were an additional 43 recorded deaths for total mortality

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Block randomisation with a block size of 8 generated by computer, stratified by age

Allocation concealment (selection bias)

Low risk

Central randomisation. Patients were sent yearly supplies of calendar packs containing their medication or matching placebos identical in appearance

Blinding of participants and personnel (performance bias)
All outcomes

Low risk

All study investigators, personnel and participants were unaware of the participants' treatment assignments
Patients were sent packs containing medication or matching placebos identical in appearance

An independent committee monitored the "safety and overall quality and scientific integrity" of the trial, which was blinded to treatment assignment
All the information was supplied by Nancy Cook (WACS statistician, 23 June 2008)

Blinding of outcome assessment (detection bias)
All outcomes

Low risk

An independent committee monitored the "safety and overall quality and scientific integrity" of the trial, which was blinded to treatment assignment
All the information was supplied by Nancy Cook (WACS statistician, 23 June 2008)

Comments: this trial had objective outcomes

Incomplete outcome data (attrition bias)
All outcomes

Unclear risk

Unknown vital status for 194 patients in the folic acid group and 207 patients in the placebo group. All the patients were included in the primary analysis, but how was not described

Selective reporting (reporting bias)

Low risk

The study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified

Other bias

Low risk

WENBIT 2008

Methods

Multicentre study

Country: Norway

Follow‐up period: 4 years

Participants

3096 patients randomised (folic acid, vitamins B6 and B12: 772 versus folic acid, vitamin B12: 772 versus vitamin B6: 772 versus placebo: 780)

  • Gender (% men)

  1. Folic acid, vitamins B6 and B12: 81.2%

  2. Folic acid, vitamin B12: 80.4%

  3. Vitamin B6: 80.2%

  4. Placebo: 76.5%

  • Age (mean ± SD, years):

  1. Folic acid, vitamins B6 and B12: 61.7 ± 10.3

  2. Folic acid, vitamin B12: 61.3 ± 10.0

  3. Vitamin B6: 61.4 ± 9.7

  4. Placebo: 62.0 ± 9.9

  • Inclusion criteria:

  1. Age: 18 years or older

  2. Undergoing coronary angiography for suspected coronary artery disease and/or aortic valve stenosis at the 2 university hospitals in western Norway

  • Exclusion criteria:

  1. Unavailability for follow‐up

  2. Participation in other trials

  3. History of alcohol abuse, serious mental illness or cancer

Interventions

  • Intervention:

  1. Folic acid (group 1): 0.8 mg; vitamin B12: 0.4 mg; vitamin B6: 40 mg per day

  2. Folic acid (group 2): 0.8 mg; vitamin B12: 0.4 mg per day

  3. Vitamin B6 (group 3): 40 mg per day

  • Control: placebo

  • Co‐interventions: statins, insulin, aspirin, clopidogrel, beta‐blockers, ACE inhibitors/ARBs, calcium channel blockers, loop diuretics, oral antidiabetics, medication for chronic obstructive pulmonary disease

Duration of treatment: not described

Outcomes

  • Primary outcome (composite):

  1. All‐cause death, non‐fatal acute myocardial infarction, acute hospitalisation for unstable angina pectoris and non‐fatal thromboembolic stroke

  • Secondary outcomes:

  1. Acute myocardial infarction

  2. Acute hospitalisation for angina pectoris

  3. Stable angina pectoris with angiographically verified progression

  4. Myocardial revascularisation procedures

  5. Stroke

  6. Incident cases of cancer

Notes

  • Study phase: III, registered (ClinicalTrials.gov number NCT00354081)

  • A priori sample size estimation: sample of 3088 participants to detect a 20% reduction in the primary endpoint during 4 years of follow‐up with a statistical power of 80% at a 2‐sided significance level of 0.05

  • Sponsors: the Advanced Research Program and Research Council of Norway, the Norwegian Foundation for Health and Rehabilitation, the Norwegian Heart and Lung Patient Organisation, the Norwegian Ministry of Health and Care Services, the Western Norway Regional Health Authority, the Department of Heart Disease at Haukeland University Hospital, Locus for Homocysteine and Related Vitamins at the University of Bergen, Locus for Cardiac Research at the University of Bergen, the Foundation to Promote Research Into Functional Vitamin B12 Deficiency, Bergen, Norway, and Alpharma Inc, Copenhagen, Denmark

  • The study medication was provide by Alpharma, which had no access to study data and did not participate in data analysis or interpretation, or in the preparation, review or approval of the manuscript

  • Other: the first 90 participants were randomised before undergoing angiography in order to ensure no effects on blood indexes from the invasive procedure. Subsequent participants were randomised after baseline angiography

  • This trial was stopped due to no beneficial effects and a suggested increased risk of cancer from B vitamin treatment

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Unclear risk

2 x 2 factorial design with block randomisation, with a block size of 20

Allocation concealment (selection bias)

Low risk

Centralised independently by the manufacturer (Alpharma)

Study nurses received coded boxes provided to participants in numerical order. The codes were kept by the manufacturer until eligibility data were complete

Blinding of participants and personnel (performance bias)
All outcomes

Low risk

Vitamins were manufactured to be indistinguishable in colour, weight or ability to be dissolved in water. Endpoints adjudicated by an independent committee unaware of patient's assignment

Blinding of outcome assessment (detection bias)
All outcomes

Low risk

Quote: "end‐points committees were unaware of the treatment allocation"

Incomplete outcome data (attrition bias)
All outcomes

High risk

6 patients (0.2% from the sample) withdrew consent to participate in the trial and were excluded from the analysis. Due to the media impact of the NORVIT interim results 692 patients were asked to stop the medication Outcome data available for 86% of patients at the final visit

Selective reporting (reporting bias)

Low risk

The study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified

Other bias

Low risk

ACE: angiotensin‐converting enzyme
ARB: angiotensin receptor blockers
CAD: coronary artery disease
CHD: coronary heart disease
CK‐MB: creatine kinase‐MB
CVD: cardiovascular disease
ECG: electrocardiogram
HLI: homocysteine‐lowering interventions
ITT: intention‐to‐treat
MI: myocardial infarction
RCT: randomised controlled trial
SD: standard deviation
t‐Hcy: total homocysteine

Characteristics of excluded studies [ordered by study ID]

Jump to:

Study

Reason for exclusion

Bazzano 2006

Systematic review

Clarke 2010

Systematic review

Cui 2010

Observational study

Deshmukh 2010

Randomised clinical trial that did not assess patient‐oriented outcomes and excluded the pre‐defined outcomes for this Cochrane Review

Durga 2011

Randomised clinical trial that did not assess patient‐oriented outcomes and excluded the pre‐defined outcomes for this Cochrane Review

Earnest 2012

Randomised clinical trial with follow‐up of less than 1 year

Ebbing 2009

Combined analyses of NORVIT 2006 and WENBIT 2008

Ebbing 2009a

Combined analyses of NORVIT 2006 and WENBIT 2008

FINEST 2006

Randomised clinical trial with follow‐up of less than 1 year

Green 2010

Randomised clinical trial that did not assess patient‐oriented outcomes and excluded the pre‐defined outcomes for this Cochrane Review

Holmes 2011

Meta‐analysis of genetic studies and randomised trials

Huang 2012

Systematic review

Huo 2012

Systematic review

Imasa 2009

Randomised clinical trial with follow‐up of less than 1 year

Jardine 2012

Systematic review in people with kidney disease

Ji 2013

Systematic review of randomised clinical trials

Lange 2004

Randomised clinical trial with follow‐up of less than 1 year

Lee 2010

Systematic review

Lonn 2007

Narrative review

Mager 2009

Observational study

Manolescu 2010

Narrative review

Mei 2010

Systematic review of randomised clinical trials including pre‐existing cardio‐cerebrovascular or renal disease patients

Miller 2010

Systematic review

Moghaddasi 2010

Case‐control study

Méndez‐González 2010

Narrative review

Ntaios 2009

Narrative review

Ntaios 2010

Randomised clinical trial that did not assess patient‐oriented outcomes such as was pre‐defined for this Cochrane Review

PACIFIC 2002

Randomised clinical trial with follow‐up of less than 1 year

Pan 2012

Systematic review

Rautiainen 2010

Observational study

Sharifi 2010

Randomised clinical trial that did not assess patient‐oriented outcomes and excluded the pre‐defined outcomes for this Cochrane Review

Shidfar 2009

Randomised clinical trial that evaluated the effects of folate supplementation on lowering homocysteine levels and changes in total antioxidant capacity in asymptomatic hypercholesteraemic adults under lovastatin treatment. It did not include the pre‐defined outcomes for this Cochrane Review

Sudchada 2012

Systematic review

Swiss 2002

Randomised clinical trial with follow‐up of less than 1 year

Tighe 2011

Randomised clinical trial that evaluated the effects of folate supplementation on lowering homocysteine levels. It did not include the pre‐defined outcomes for this Cochrane Review

Vesin 2007

Narrative review

Wang 2007

Systematic review

Wang 2012

Systematic review

Wierzbicki 2007

Narrative review

Yang 2012

Systematic review

Zappacosta 2013

Randomised clinical trial that did not assess patient‐oriented outcomes and excluded the pre‐defined outcomes for this Cochrane Review

Zhang 2009

Systematic review

Zhang 2013

Systematic review

Zhou 2011

Systematic review

Data and analyses

Open in table viewer
Comparison 1. Homocysteine‐lowering treatment versus other (any comparisons)

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Myocardial infarction Show forest plot

12

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

Analysis 1.1

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 1 Myocardial infarction.

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 1 Myocardial infarction.

1.1 Homocysteine‐lowering versus placebo

11

43780

Risk Ratio (M‐H, Random, 95% CI)

1.02 [0.95, 1.10]

1.2 Homocysteine‐lowering treatment at high dose versus low dose

1

3649

Risk Ratio (M‐H, Random, 95% CI)

0.90 [0.66, 1.23]

2 Stroke Show forest plot

10

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

Analysis 1.2

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 2 Stroke.

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 2 Stroke.

2.1 Homocysteine‐lowering treatment versus placebo

9

41305

Risk Ratio (M‐H, Random, 95% CI)

0.91 [0.82, 1.00]

2.2 Homocysteine‐lowering treatment at high dose versus low dose

1

3649

Risk Ratio (M‐H, Random, 95% CI)

1.04 [0.84, 1.29]

3 First unstable angina pectoris episode requiring hospitalisation Show forest plot

4

12644

Risk Ratio (M‐H, Random, 95% CI)

0.98 [0.80, 1.21]

Analysis 1.3

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 3 First unstable angina pectoris episode requiring hospitalisation.

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 3 First unstable angina pectoris episode requiring hospitalisation.

4 Death from any cause Show forest plot

11

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

Analysis 1.4

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 4 Death from any cause.

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 4 Death from any cause.

4.1 Homocysteine‐lowering treatment versus placebo

10

41898

Risk Ratio (M‐H, Random, 95% CI)

1.01 [0.96, 1.07]

4.2 Homocysteine‐lowering treatments at high dose versus low dose

1

3649

Risk Ratio (M‐H, Random, 95% CI)

0.86 [0.66, 1.11]

5 Serious adverse events (cancer) Show forest plot

7

32869

Risk Ratio (M‐H, Random, 95% CI)

1.06 [0.98, 1.13]

Analysis 1.5

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 5 Serious adverse events (cancer).

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 5 Serious adverse events (cancer).

Open in table viewer
Comparison 2. Homocysteine‐lowering treatment versus other (Sensitivity analysis)

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Myocardial infarction Show forest plot

7

40532

Risk Ratio (M‐H, Random, 95% CI)

1.02 [0.95, 1.09]

Analysis 2.1

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 1 Myocardial infarction.

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 1 Myocardial infarction.

1.1 Trials with low risk of bias (mixed populations)

6

35090

Risk Ratio (M‐H, Random, 95% CI)

1.02 [0.95, 1.10]

1.2 Trials with low risk of bias (only women included)

1

5442

Risk Ratio (M‐H, Random, 95% CI)

0.88 [0.63, 1.22]

2 Stroke Show forest plot

7

40532

Risk Ratio (M‐H, Random, 95% CI)

0.91 [0.81, 1.01]

Analysis 2.2

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 2 Stroke.

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 2 Stroke.

2.1 Trials with low risk of bias (mixed populations)

6

35090

Risk Ratio (M‐H, Random, 95% CI)

0.89 [0.81, 0.98]

2.2 Trials with low risk of bias (only women included)

1

5442

Risk Ratio (M‐H, Random, 95% CI)

1.14 [0.83, 1.57]

3 First unstable angina pectoris episode requiring hospitalisation Show forest plot

3

12361

Risk Ratio (M‐H, Random, 95% CI)

0.99 [0.79, 1.24]

Analysis 2.3

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 3 First unstable angina pectoris episode requiring hospitalisation.

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 3 First unstable angina pectoris episode requiring hospitalisation.

4 Death from any cause Show forest plot

8

41022

Risk Ratio (M‐H, Random, 95% CI)

1.03 [0.95, 1.12]

Analysis 2.4

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 4 Death from any cause.

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 4 Death from any cause.

4.1 Trials with low risk of bias (mixed populations)

7

35580

Risk Ratio (M‐H, Random, 95% CI)

1.05 [0.95, 1.15]

4.2 Trials with low risk of bias (only women included)

1

5442

Risk Ratio (M‐H, Random, 95% CI)

0.98 [0.83, 1.15]

Homocysteine metabolism (Reproduced with Dr Félix TM's permission from Brustolin 2010)
Figures and Tables -
Figure 1

Homocysteine metabolism (Reproduced with Dr Félix TM's permission from Brustolin 2010)

Study flow diagram for this update
Figures and Tables -
Figure 2

Study flow diagram for this update

Methodological quality graph: review authors' judgements about each methodological quality item presented as percentages across all included studies
Figures and Tables -
Figure 3

Methodological quality graph: review authors' judgements about each methodological quality item presented as percentages across all included studies

Methodological quality summary: review authors' judgements about each methodological quality item for each included study
Figures and Tables -
Figure 4

Methodological quality summary: review authors' judgements about each methodological quality item for each included study

Trial sequential analysis on myocardial infarction in 11 trials investigating homocysteine‐lowering interventions versus placebo Trial sequential analysis of homocysteine‐lowering interventions versus placebo on myocardial infarction based on the diversity‐adjusted required information size (DARIS) of 10,888 patients. This DARIS was calculated based upon a proportion of patients with myocardial infarction of 6.17% in the control group; a RRR of 20% in the experimental intervention group; an alpha (α) of 5%; a beta (β) of 20%; and a diversity of 0%. The cumulative Z‐curve (blue line) does not cross the conventional alpha of 5%. After the fourth trial, the cumulative Z‐curve crosses the trial sequential beta‐spending monitoring boundary, showing that the area of futility has been reached. This suggests that no more trials may be needed to disprove an intervention effect of 20% relative risk reduction. Smaller risk reductions might still require further trials.
Figures and Tables -
Figure 5

Trial sequential analysis on myocardial infarction in 11 trials investigating homocysteine‐lowering interventions versus placebo

Trial sequential analysis of homocysteine‐lowering interventions versus placebo on myocardial infarction based on the diversity‐adjusted required information size (DARIS) of 10,888 patients. This DARIS was calculated based upon a proportion of patients with myocardial infarction of 6.17% in the control group; a RRR of 20% in the experimental intervention group; an alpha (α) of 5%; a beta (β) of 20%; and a diversity of 0%. The cumulative Z‐curve (blue line) does not cross the conventional alpha of 5%. After the fourth trial, the cumulative Z‐curve crosses the trial sequential beta‐spending monitoring boundary, showing that the area of futility has been reached. This suggests that no more trials may be needed to disprove an intervention effect of 20% relative risk reduction. Smaller risk reductions might still require further trials.

Funnel plot of data from the meta‐analysis of the effects of homocysteine‐lowering interventions for preventing myocardial infarction The circles show the point estimates of the included randomised clinical trials. The pattern of distribution resembles an inverted funnel. Larger trials are upper and closer to the pooled estimate. The effect sizes of the smaller studies are more or less symmetrically distributed around the pooled estimate. This figure shows a low risk of publication bias.
Figures and Tables -
Figure 6

Funnel plot of data from the meta‐analysis of the effects of homocysteine‐lowering interventions for preventing myocardial infarction

The circles show the point estimates of the included randomised clinical trials. The pattern of distribution resembles an inverted funnel. Larger trials are upper and closer to the pooled estimate. The effect sizes of the smaller studies are more or less symmetrically distributed around the pooled estimate. This figure shows a low risk of publication bias.

Trial sequential analysis on stroke in nine trials investigating homocysteine‐lowering interventions versus placebo Trial sequential analysis of homocysteine‐lowering interventions versus placebo on stroke based on the diversity‐adjusted required information size (DARIS) of 17,679 patients. This DARIS was calculated based upon a proportion of patients with stroke of 5.13% in the control group; a RRR of 20% in the experimental intervention group; an alpha (α) of 5%; a beta (β) of 20%; and a diversity of 26%. The cumulative Z‐curve (blue line) temporally crosses the conventional alpha of 5%, but reverts to insignificant values. The cumulative Z‐curve never crosses the trial sequential alpha‐spending monitoring boundaries. After the third trial, the cumulative Z‐curve crosses the trial sequential beta‐spending monitoring boundary, showing that the area of futility has been reached. This suggests that no more trials may be needed to disprove an intervention effect of 20% relative risk reduction. Smaller risk reductions might still require further trials.
Figures and Tables -
Figure 7

Trial sequential analysis on stroke in nine trials investigating homocysteine‐lowering interventions versus placebo

Trial sequential analysis of homocysteine‐lowering interventions versus placebo on stroke based on the diversity‐adjusted required information size (DARIS) of 17,679 patients. This DARIS was calculated based upon a proportion of patients with stroke of 5.13% in the control group; a RRR of 20% in the experimental intervention group; an alpha (α) of 5%; a beta (β) of 20%; and a diversity of 26%. The cumulative Z‐curve (blue line) temporally crosses the conventional alpha of 5%, but reverts to insignificant values. The cumulative Z‐curve never crosses the trial sequential alpha‐spending monitoring boundaries. After the third trial, the cumulative Z‐curve crosses the trial sequential beta‐spending monitoring boundary, showing that the area of futility has been reached. This suggests that no more trials may be needed to disprove an intervention effect of 20% relative risk reduction. Smaller risk reductions might still require further trials.

Funnel plot of data from the meta‐analysis of the effects of homocysteine‐lowering interventions for preventing stroke The circles show the point estimates of the included randomised clinical trials. The pattern of distribution resembles an inverted funnel. Larger trials are closer and upper to the pooled estimate. The effect sizes of the smaller trials are lower and more or less symmetrically distributed around the pooled estimate. This figure shows a low risk of publication bias.
Figures and Tables -
Figure 8

Funnel plot of data from the meta‐analysis of the effects of homocysteine‐lowering interventions for preventing stroke

The circles show the point estimates of the included randomised clinical trials. The pattern of distribution resembles an inverted funnel. Larger trials are closer and upper to the pooled estimate. The effect sizes of the smaller trials are lower and more or less symmetrically distributed around the pooled estimate. This figure shows a low risk of publication bias.

Trial sequential analysis on death from any cause in 10 trials investigating homocysteine‐lowering interventions versus placebo Trial sequential analysis of homocysteine‐lowering interventions versus placebo on death from any cause based on the diversity‐adjusted required information size (DARIS) of 10,419 patients. This DARIS was calculated based upon a proportion of death from any cause out of 13% in the control group; a RRR of 15% in the experimental intervention group; an alpha (α) of 5%; a beta (β) of 20%; and a diversity of 16%. After the third trial, the cumulative Z‐curve (blue line) crosses the trial sequential beta‐spending monitoring boundary, showing that the area of futility has been reached. This suggests that no more trials may be needed to disprove an intervention effect of 15% relative risk reduction. Smaller risk reductions might still require further trials.
Figures and Tables -
Figure 9

Trial sequential analysis on death from any cause in 10 trials investigating homocysteine‐lowering interventions versus placebo

Trial sequential analysis of homocysteine‐lowering interventions versus placebo on death from any cause based on the diversity‐adjusted required information size (DARIS) of 10,419 patients. This DARIS was calculated based upon a proportion of death from any cause out of 13% in the control group; a RRR of 15% in the experimental intervention group; an alpha (α) of 5%; a beta (β) of 20%; and a diversity of 16%. After the third trial, the cumulative Z‐curve (blue line) crosses the trial sequential beta‐spending monitoring boundary, showing that the area of futility has been reached. This suggests that no more trials may be needed to disprove an intervention effect of 15% relative risk reduction. Smaller risk reductions might still require further trials.

Funnel plot of data from the meta‐analysis of the effects of homocysteine‐lowering interventions for preventing death from any cause This figure shows a low risk of publication bias. The circles show the point estimates of the included randomised clinical trials. The pattern of distribution simulates an inverted funnel. Larger trials are closer and upper to the pooled estimate. The effect sizes of the smaller trials are lower and more or less symmetrically distributed around the pooled estimate. This figure shows a low risk of publication bias.
Figures and Tables -
Figure 10

Funnel plot of data from the meta‐analysis of the effects of homocysteine‐lowering interventions for preventing death from any cause

This figure shows a low risk of publication bias. The circles show the point estimates of the included randomised clinical trials. The pattern of distribution simulates an inverted funnel. Larger trials are closer and upper to the pooled estimate. The effect sizes of the smaller trials are lower and more or less symmetrically distributed around the pooled estimate. This figure shows a low risk of publication bias.

Trial sequential analysis on adverse events (cancer) in seven trials investigating homocysteine‐lowering interventions versus placebo Trial sequential analysis of homocysteine‐lowering interventions versus placebo on adverse events (cancer) based on the diversity‐adjusted required information size (DARIS) of 17,676 patients. This DARIS was calculated based upon a proportion of patients developing cancer of 9% in the control group; a RRR of 13% in the experimental intervention group; an alpha (α) of 5%; a beta (β) of 20%; and a diversity of 0%. The cumulative Z‐curve (blue line) crosses the trials sequential beta‐spending monitoring boundary, showing that the area of futility has been reached. This suggests that no more trials are needed to disprove an intervention effect of 13% relative risk reduction.
Figures and Tables -
Figure 11

Trial sequential analysis on adverse events (cancer) in seven trials investigating homocysteine‐lowering interventions versus placebo

Trial sequential analysis of homocysteine‐lowering interventions versus placebo on adverse events (cancer) based on the diversity‐adjusted required information size (DARIS) of 17,676 patients. This DARIS was calculated based upon a proportion of patients developing cancer of 9% in the control group; a RRR of 13% in the experimental intervention group; an alpha (α) of 5%; a beta (β) of 20%; and a diversity of 0%. The cumulative Z‐curve (blue line) crosses the trials sequential beta‐spending monitoring boundary, showing that the area of futility has been reached. This suggests that no more trials are needed to disprove an intervention effect of 13% relative risk reduction.

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 1 Myocardial infarction.
Figures and Tables -
Analysis 1.1

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 1 Myocardial infarction.

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 2 Stroke.
Figures and Tables -
Analysis 1.2

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 2 Stroke.

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 3 First unstable angina pectoris episode requiring hospitalisation.
Figures and Tables -
Analysis 1.3

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 3 First unstable angina pectoris episode requiring hospitalisation.

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 4 Death from any cause.
Figures and Tables -
Analysis 1.4

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 4 Death from any cause.

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 5 Serious adverse events (cancer).
Figures and Tables -
Analysis 1.5

Comparison 1 Homocysteine‐lowering treatment versus other (any comparisons), Outcome 5 Serious adverse events (cancer).

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 1 Myocardial infarction.
Figures and Tables -
Analysis 2.1

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 1 Myocardial infarction.

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 2 Stroke.
Figures and Tables -
Analysis 2.2

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 2 Stroke.

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 3 First unstable angina pectoris episode requiring hospitalisation.
Figures and Tables -
Analysis 2.3

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 3 First unstable angina pectoris episode requiring hospitalisation.

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 4 Death from any cause.
Figures and Tables -
Analysis 2.4

Comparison 2 Homocysteine‐lowering treatment versus other (Sensitivity analysis), Outcome 4 Death from any cause.

Summary of findings for the main comparison. Homocysteine‐lowering interventions (folic acid, vitamin B6 and vitamin B12) compared with placebo or standard care for preventing cardiovascular events

Homocysteine‐lowering interventions (folic acid, vitamin B6 and vitamin B12) compared with placebo or standard care for preventing cardiovascular events

Patient or population: Adults at risk of or with established cardiovascular disease
Settings: outpatients
Intervention: homocysteine‐lowering interventions (folic acid, vitamin B6 and vitamin B12)
Comparison: placebo or standard care

Outcomes

Illustrative comparative risks* (95% CI)

Relative effect
(95% CI)

No of participants
(studies)

Quality of the evidence
(GRADE)

Comments

Assumed risk

Corresponding risk

Placebo or standard care

Homocysteine‐lowering interventions (folic acid, vitamin B6 and vitamin B12)

Non‐fatal or fatal myocardial infarction
Follow‐up: 1 to 7.3 years

Study population

RR 1.02
(0.95 to 1.1)

43,290
(11 studies)

⊕⊕⊕⊕
high1,2

62 per 1000

64 per 1000
(59 to 69)

Stroke
Follow‐up: 1 to 7.3 years

Study population

RR 0.91
(0.82 to 1.01)

40,815
(9 studies)

⊕⊕⊕⊕
high3,4

52 per 1000

47 per 1000
(43 to 52)

Death from any cause
Follow‐up: 1 to 7.3 years

Study population

RR 1.01
(0.96 to 1.07)

41,898
(10 studies)

⊕⊕⊕⊕
high5,6

130 per 1000

131 per 1000
(125 to 139)

Cancer
Follow‐up: 3.4 to 7.3 years

Study population

RR 1.06
(0.98 to 1.13)

32,869
(7 studies)

⊕⊕⊕⊕
high7,8

91 per 1000

96 per 1000
(89 to 102)

*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
CI: confidence interval; RR: risk ratio

GRADE Working Group grades of evidence
High quality: Further research is very unlikely to change our confidence in the estimate of effect.
Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
Very low quality: We are very uncertain about the estimate.

1I² = 0%.
243,290 participants with 2986 events.
3I² = 13%.
440,815 participants with 1940 events.
5I² = 6%.
641,898 participants with 5286 events.
7I² = 0%.
832,869 participants with 2892 events.

Figures and Tables -
Summary of findings for the main comparison. Homocysteine‐lowering interventions (folic acid, vitamin B6 and vitamin B12) compared with placebo or standard care for preventing cardiovascular events
Comparison 1. Homocysteine‐lowering treatment versus other (any comparisons)

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Myocardial infarction Show forest plot

12

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

1.1 Homocysteine‐lowering versus placebo

11

43780

Risk Ratio (M‐H, Random, 95% CI)

1.02 [0.95, 1.10]

1.2 Homocysteine‐lowering treatment at high dose versus low dose

1

3649

Risk Ratio (M‐H, Random, 95% CI)

0.90 [0.66, 1.23]

2 Stroke Show forest plot

10

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

2.1 Homocysteine‐lowering treatment versus placebo

9

41305

Risk Ratio (M‐H, Random, 95% CI)

0.91 [0.82, 1.00]

2.2 Homocysteine‐lowering treatment at high dose versus low dose

1

3649

Risk Ratio (M‐H, Random, 95% CI)

1.04 [0.84, 1.29]

3 First unstable angina pectoris episode requiring hospitalisation Show forest plot

4

12644

Risk Ratio (M‐H, Random, 95% CI)

0.98 [0.80, 1.21]

4 Death from any cause Show forest plot

11

Risk Ratio (M‐H, Random, 95% CI)

Subtotals only

4.1 Homocysteine‐lowering treatment versus placebo

10

41898

Risk Ratio (M‐H, Random, 95% CI)

1.01 [0.96, 1.07]

4.2 Homocysteine‐lowering treatments at high dose versus low dose

1

3649

Risk Ratio (M‐H, Random, 95% CI)

0.86 [0.66, 1.11]

5 Serious adverse events (cancer) Show forest plot

7

32869

Risk Ratio (M‐H, Random, 95% CI)

1.06 [0.98, 1.13]

Figures and Tables -
Comparison 1. Homocysteine‐lowering treatment versus other (any comparisons)
Comparison 2. Homocysteine‐lowering treatment versus other (Sensitivity analysis)

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Myocardial infarction Show forest plot

7

40532

Risk Ratio (M‐H, Random, 95% CI)

1.02 [0.95, 1.09]

1.1 Trials with low risk of bias (mixed populations)

6

35090

Risk Ratio (M‐H, Random, 95% CI)

1.02 [0.95, 1.10]

1.2 Trials with low risk of bias (only women included)

1

5442

Risk Ratio (M‐H, Random, 95% CI)

0.88 [0.63, 1.22]

2 Stroke Show forest plot

7

40532

Risk Ratio (M‐H, Random, 95% CI)

0.91 [0.81, 1.01]

2.1 Trials with low risk of bias (mixed populations)

6

35090

Risk Ratio (M‐H, Random, 95% CI)

0.89 [0.81, 0.98]

2.2 Trials with low risk of bias (only women included)

1

5442

Risk Ratio (M‐H, Random, 95% CI)

1.14 [0.83, 1.57]

3 First unstable angina pectoris episode requiring hospitalisation Show forest plot

3

12361

Risk Ratio (M‐H, Random, 95% CI)

0.99 [0.79, 1.24]

4 Death from any cause Show forest plot

8

41022

Risk Ratio (M‐H, Random, 95% CI)

1.03 [0.95, 1.12]

4.1 Trials with low risk of bias (mixed populations)

7

35580

Risk Ratio (M‐H, Random, 95% CI)

1.05 [0.95, 1.15]

4.2 Trials with low risk of bias (only women included)

1

5442

Risk Ratio (M‐H, Random, 95% CI)

0.98 [0.83, 1.15]

Figures and Tables -
Comparison 2. Homocysteine‐lowering treatment versus other (Sensitivity analysis)