Diabetes mellitus, glycemic control, and incident depressive symptoms among 70-to 79-year-old persons

Background: Cross-sectional studies find an elevated prevalence of depression among subjects with diabetes mellitus ( DM). The causal mechanisms and temporal sequence of this association have not been clearly delineated. This study investigated the prospective relationship between DM and depressive symptoms. Methods: The Health, Aging, and Body Composition Study was a cohort study conducted in the metropolitan areas of Memphis, Tenn, and Pittsburgh, Pa. The analysis included 2522 community-dwelling subjects, aged 70 to 79 years, without baseline depressive symptoms. Incident depressed mood was defined as use of antidepressants at follow-up visits or presence of depressive symptoms ( score >= 10 on the 10-item Center for Epidemiological Studies Depression scale). Presence of incident depressed mood at 2 consecutive annual clinic visits defined the incidence of recurrent depressed mood. Diabetes mellitus status, glycosylated hemoglobin ( HbA1c) level, and DM-related comorbidities were assessed at baseline. Diabetes mellitus status was further characterized as absent, controlled ( HbA1c level < 7%), or uncontrolled ( HbA1c level >= 7%). Discrete time survival analysis was used to estimate depressive events risk. Results: During a mean follow-up of 5.9 years, participants with DM had a higher age-, sex-, race-, and site-adjusted incidence of depressed mood ( 23.5% vs 19.0%) ( P = .02) and recurrent depressed mood ( 8.8% vs 4.3%) ( P < .001) than those without DM. Diabetes mellitus was associated with a 30% increased risk of incident depressed mood ( odds ratio [ OR], 1.31; 95% confidence interval [ CI], 1.07-1.61), which was attenuated after adjustment for DM-related comorbidities ( OR, 1.20; CI, 0.97-1.48). A stronger relationship was observed between DM and recurrent depressed mood ( OR, 1.91; CI, 1.32-2.76), particularly among participants with poor glycemic control. Conclusion: Among well-functioning older adults, DM is associated with increased risk of depressive symptoms.