Objective: To assess whether Medicare fee-for-service beneficiaries with depression and diabetes had a higher mortality rate over a 2-year period compared with beneficiaries with diabetes alone.

Design: Evidence of depression was based on a physician diagnosis or self-reported prescription of an antidepressant in the year prior to screening, or a score of > or = 3 on the Patient Health Questionnaire two-item questionnaire. Mortality was assessed bi-monthly by checking Medicare claims and eligibility files or from information from telephone contact with the participant's family. Cox proportional hazard regression models were used to calculate adjusted hazard ratios of death in depressed versus nondepressed beneficiaries with diabetes.

Participants: A total of 10,704 beneficiaries with diabetes enrolled in a disease management program were surveyed with a health assessment questionnaire and followed over a two-year period.

Main results: Comorbid depression in Medicare beneficiaries with diabetes participating in a disease management program was associated with an increased risk for all-cause mortality over a two-year period of approximately 36% to 38%, depending on the definition of depression that was used. No significant increase in rates of cause-specific mortality from macrovascular disease were found in depressed versus nondepressed beneficiaries.

Conclusion: Among a large Medicare cohort of fee-for-service beneficiaries with diabetes, comorbid depression was associated with an increase in all-cause mortality over a two-year period. Future research will be required to determine whether the increase in mortality associated with depression is due to potential behavioral mediators (i.e., smoking, poor adherence to diet) or physiologic abnormalities (i.e., hypothalamic-pituitary axis dysregulation) associated with depression.