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. 2019 Apr 2;170(7):433-442.
doi: 10.7326/M18-2574. Epub 2019 Mar 12.

Dual Receipt of Prescription Opioids From the Department of Veterans Affairs and Medicare Part D and Prescription Opioid Overdose Death Among Veterans: A Nested Case-Control Study

Patience Moyo  1 , Xinhua Zhao  2 , Carolyn T Thorpe  3 , Joshua M Thorpe  3 , Florentina E Sileanu  2 , John P Cashy  2 , Jennifer A Hale  2 , Maria K Mor  4 , Thomas R Radomski  5 , Julie M Donohue  4 , Leslie R M Hausmann  5 , Joseph T Hanlon  6 , Chester B Good  7 , Michael J Fine  5 , Walid F Gellad  8
Affiliations

Dual Receipt of Prescription Opioids From the Department of Veterans Affairs and Medicare Part D and Prescription Opioid Overdose Death Among Veterans: A Nested Case-Control Study

Patience Moyo et al. Ann Intern Med. .

Abstract

Background: More than half of enrollees in the U.S. Department of Veterans Affairs (VA) are also covered by Medicare and can choose to receive their prescriptions from VA or from Medicare-participating providers. Such dual-system care may lead to unsafe opioid use if providers in these 2 systems do not coordinate care or if prescription use is not tracked between systems.

Objective: To evaluate the association between dual-system opioid prescribing and death from prescription opioid overdose.

Design: Nested case-control study.

Setting: VA and Medicare Part D.

Participants: Case and control patients were identified from all veterans enrolled in both VA and Part D who filled at least 1 opioid prescription from either system. The 215 case patients who died of a prescription opioid overdose in 2012 or 2013 were matched (up to 1:4) with 833 living control patients on the basis of date of death (that is, index date), using age, sex, race/ethnicity, disability, enrollment in Medicaid or low-income subsidies, managed care enrollment, region and rurality of residence, and a medication-based measure of comorbid conditions.

Measurements: The exposure was the source of opioid prescriptions within 6 months of the index date, categorized as VA only, Part D only, or VA and Part D (that is, dual use). The outcome was unintentional or undetermined-intent death from prescription opioid overdose, identified from the National Death Index. The association between this outcome and source of opioid prescriptions was estimated using conditional logistic regression with adjustment for age, marital status, prescription drug monitoring programs, and use of other medications.

Results: Among case patients, the mean age was 57.3 years (SD, 9.1), 194 (90%) were male, and 181 (84%) were non-Hispanic white. Overall, 60 case patients (28%) and 117 control patients (14%) received dual opioid prescriptions. Dual users had significantly higher odds of death from prescription opioid overdose than those who received opioids from VA only (odds ratio [OR], 3.53 [95% CI, 2.17 to 5.75]; P < 0.001) or Part D only (OR, 1.83 [CI, 1.20 to 2.77]; P = 0.005).

Limitation: Data are from 2012 to 2013 and cannot capture prescriptions obtained outside the VA or Medicare Part D systems.

Conclusion: Among veterans enrolled in VA and Part D, dual use of opioid prescriptions was independently associated with death from prescription opioid overdose. This risk factor for fatal overdose among veterans underscores the importance of care coordination across health care systems to improve opioid prescribing safety.

Primary funding source: U.S. Department of Veterans Affairs.

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Conflict of interest statement

Authors not named here have disclosed no conflicts of interest. Disclosures can also be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M18–2574.

Figures

Figure 1.
Figure 1.. Selection criteria for case and control patients.
* MME = morphine milligram equivalent; VA = U.S. Department of Veterans Affairs. * Matching proceeded in 4 steps: The first 3 allowed replacement of control patients, and the final step was without replacement. Therefore, unique control patients could be possible matches for ≥1 case patient before the last step. First, we matched control patients to case patients on the 5 time-invariant variables (birthdate ±5 y, sex, race/ethnicity, region of residence, and rurality of residence), and assigned the date of death from each case patient as the index date for matched control patients (n = 1 522 446 unique control patients matched to n = 219 case patients). Second, we applied the same exclusion criteria to control patients as described for case patients (n = 271 805 unique control patients matched to n = 219 case patients). Third, we matched case and control patients on the 4 time-variant variables (disability as the reason for Medicare enrollment [year of death], enrollment in Medicaid and Part D low-income subsidy [prior 6 mo], Medicare managed care enrollment [prior6 mo], and medication-based comorbidity index [Rx-Risk, prior 6 mo]; n = 34 289 unique control patients were matched to n = 215 case patients, including 10 case patients with <4 control patients). Finally, we randomly sampled up to 4 control patients per case patient without replacement (n = 833), where 205 case patients had 4 control patients each, 7 had 1 control patient, and 3 had 2 control patients. The final number of case patients was 215 after exclusion of 4 who lacked any matches on the 4 time-varying variables.
Figure 2.
Figure 2.. Sensitivity analysis to identify the level of confounding necessary to nullify the association between receipt of prescription opioids from VA and Medicare Part D and unintentional death from prescription opioid overdose among veterans.
The plot was drawn by assuming a fixed prevalence (50%) of the unmeasured confounder among exposed persons (dual users) and a plausible prevalence among unexposed persons (VA-only users) ranging from 2% to 12%. The relative risk ratio of a confounder with opioid overdose death needed to nullify the observed adjusted OR ranged from 6.5 to 34.1 (x-axis), and the corresponding OR of the confounder with dual use ranged from 49.0 to 7.3 (y-axis). The area above and to the right of the curved plotted line represents values of the levels of confounding necessary to produce the observed adjusted OR (3.53) in our study. The area below and to the left of the line represents levels of confounding that would not be sufficient on its own, after adjustment for observed variables, to produce the observed OR. For example, the dashed lines indicate that for a confounder with a prevalence of 50% among exposed persons and 6% among unexposed persons, a relative risk ratio ≥9.8 with opioid overdose death (x-axis), and an OR≥15.7 with dual VA and Part D use (y-axis) would be needed to nullify our observed adjusted OR. OR = odds ratio; VA = U.S. Department of Veterans Affairs.
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