Context: Depression and diabetes mellitus have been associated with an increased risk of all-cause and cardiovascular disease (CVD) mortality. However, data evaluating the joint effects of these 2 conditions on mortality are sparse.
Objectives: To evaluate the individual and joint effects of depression and diabetes on all-cause and CVD mortality rate.
Design: Prospective cohort study.
Setting: The 11 states of the Nurses' Health Study.
Participants: A total of 78 282 women who participated in the Nurses' Health Study aged 54 to 79 years at baseline in 2000 were followed up until 2006. Depression was defined as having self-reported diagnosed depression, treatment with antidepressant medications, or a score indicating severe depressive symptoms (ie, a 5-item Mental Health Index score ≤52). Self-reported type 2 diabetes was confirmed using a supplementary questionnaire.
Main outcome measures: All-cause and CVD-specific mortality rate.
Results: During 6 years of follow-up (433 066 person-years), 4654 deaths were documented, including 979 deaths from CVD. Compared with participants without either condition, the age-adjusted relative risks (RRs) (95% confidence interval) for all-cause mortality were 1.76 (1.64-1.89) for women with depression only, 1.71 (1.54-1.89) for individuals with diabetes only, and 3.11 (2.70-3.58) for women with both conditions. The corresponding age-adjusted RRs of CVD mortality were 1.81 (1.54-2.13), 2.67 (2.20-3.23), and 5.38 (4.19-6.91), respectively. These associations were attenuated after multivariate adjustment for other demographic variables, body mass index, smoking status, alcohol intake, physical activity, and major comorbidities (including hypertension, hypercholesterolemia, heart diseases, stroke, and cancer) but remained significant, with the highest RRs for all-cause and CVD mortality found in those with both conditions (2.07 [1.79-2.40] and 2.72 [2.09-3.54], respectively). Furthermore, the combination of depression with a long duration of diabetes mellitus (ie, >10 years) or insulin therapy was associated with a particularly higher risk of CVD mortality after multivariate adjustment (RRs, 3.22 and 4.90, respectively).
Conclusions: Depression and diabetes are associated with a significantly increased risk of all-cause and CVD mortality rate. The coexistence of these conditions identifies women at particularly high risk.