Objective: The goal of this study was to determine whether depressive symptoms predict type 2 diabetes.
Research design and methods: We analyzed data on depressive symptoms (including recent fatigue, sleep disturbance, feelings of hopelessness, loss of libido, and increased irritability) in a longitudinal, biracial cohort study of 11,615 initially nondiabetic adults aged 48-67 years, who were subsequently followed for 6 years for the development of type 2 diabetes.
Results: At baseline, depressive symptoms were positively associated with BMI, fasting insulin, systolic blood pressure, caloric intake, physical inactivity, and current smoking (all P < 0.05). In prospective analyses, after adjusting for age, race, sex, and education, individuals in the highest quartile of depressive symptoms had a 63% increased risk of developing diabetes compared with those in the lowest quartile (relative hazard [RH] 1.63, 95% CI 1.31-2.02). This relation persisted after adjustment for stress-associated lifestyle factors (smoking, physical activity, caloric intake, and adiposity) (1.28, 1.02-1.60) and metabolic covariates (fasting insulin and glucose, lipids, blood pressure, and adiposity) (1.38, 1.10-1.73).
Conclusions: In this cohort, depressive symptoms predicted incident type 2 diabetes. This relation is only partially explained by demographic, metabolic, and lifestyle factors. Possible neuroendocrine mediators of the stress-obesity-diabetes relationship require further evaluation in prospective cohort studies that use an established tool to assess depression and incorporate neurohormonal measurements.