Depression and Increased Mortality in Diabetes: Unexpected Causes of Death

PURPOSE Recent evidence suggests that depression is linked to increased mortal-ity among patients with diabetes. This study examines the association of depres-sion with all-cause and cause-specifi c mortality in diabetes. METHODS We conducted a prospective cohort study of primary care patients with type 2 diabetes at Group Health Cooperative in Washington state. We used the Patient Health Questionnaire (PHQ-9) to assess depression at baseline and reviewed medical records supplemented by the Washington state mortality regis-try to ascertain the causes of death. RESULTS Among a cohort of 4,184 patients, 581 patients died during the fol-low-up period. Deaths occurred among 428 (12.9%) patients with no depres-sion, among 88 (17.8%) patients with major depression, and among 65 (18.2%) patients with minor depression. Causes of death were grouped as cardiovascular disease, 42.7%; cancer, 26.9%; and deaths that were not due to cardiovascu-lar disease or cancer, 30.5%. Infections, dementia, renal failure, and chronic obstructive pulmonary disease were the most frequent causes in the latter group. Adjusting for demographic characteristics, baseline major depression (relative to no depression) was signifi cantly associated with all-cause mortality (hazard ratio [HR] = 2.26, 95 % confi dence interval [CI], 1.79-2.85), with cardiovascular mortality (HR = 2.00; 95 % CI, 1.37-2.94), and with noncardiovascular, noncancer mortality (HR = 3.35; 95 % CI, 2.30-4.89). After additional adjustment for baseline clinical characteristics and health habits, major depression was signifi cantly associ-ated only with all-cause mortality (HR = 1.52; 95 % CI, 1.19-1.95) and with death not caused by cancer or atherosclerotic cardiovascular disease (HR = 2.15; 95 % CI, 1.43-3.24). Minor depression showed similar but nonsignifi cant associations. CONCLUSIONS Patients with diabetes and coexisting depression face substantially elevated mortality risks beyond cardiovascular deaths. Ann Fam Med 2009:7:414-421. doi:10.1370/afm.998