Both depression and diabetes have been associated with an increased risk of all-cause and cardiovascular diseases (CVD) mortality. However, data evaluating the joint effects of these two conditions on mortality are sparse.
To evaluate the individual and joint effects of depression and diabetes on all-cause and CVD mortality in a prospective cohort study.
Design, Settings and Participants
A total of 78282 female participants in the Nurses' Health Study aged 54-79 years at baseline in 2000 were followed until 2006. Depression was defined as having self-reported diagnosed depression, treatment with antidepressant medications, or a score indicating severe depressive symptomatology, i.e., a five-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.
During 6 years of follow-up (433066 person-years), 4654 deaths were documented, including 979 deaths from CVD. Compared to participants without either condition, the age-adjusted relative risks (95% confidence interval, CI) 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 those with both conditions. The corresponding age-adjusted relative risks 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 relative risks for all-cause and CVD mortality found in those with both conditions (2.07 [95% CI, 1.79-2.40] and 2.72 [95% CI, 2.09-3.54], respectively). Furthermore, the combination of depression with a long duration of diabetes (i.e., >10 years) or insulin therapy was associated with particularly higher risk of CVD mortality after multivariate adjustment (relative risk=3.22 and 4.90, respectively).
Depression and diabetes are associated with significantly increased risk of all-cause and CVD mortality. The coexistence of both conditions identifies particularly high-risk women.
Keywords: depression, diabetes, prospective cohort study, morbidity