Longitudinal Association Between Depressive Symptoms and Incident Type 2 Diabetes Mellitus in Older Adults

BACKGROUND: Prospective studies indicate that a single self-report of high depressive symptoms is associated with an increased risk of developing type 2 diabetes mellitus. METHODS: We tested whether a single report of high depressive symptoms, an increase in depressive symptoms, or persistently high depressive symptoms over time were associated with the development of diabetes in adults 65 years and older. Participants from the Cardiovascular Health Study completed the 10-item Center for Epidemiological Studies-Depression Scale (CES-D) annually from 1989 to 1999. A single report of high depressive symptoms (CES-D score, >/=8), an increase in symptoms during follow-up (>/=5 from baseline), and persistently high symptoms (2 consecutive scores >/=8) were each studied in relation to incident diabetes, defined by initiation of diabetes control medications among participants who were free from diabetes at baseline (n = 4681). RESULTS: The mean CES-D score at baseline was 4.5 (SD, 4.5). The incidence rate of diabetes was 4.4 per 1000 person-years. Following adjustment for baseline demographic characteristics and measures of physical activity, smoking, alcohol intake, body mass index, and C-reactive protein during follow-up, each measure of depressive symptoms was significantly associated with incident diabetes (high baseline CES-D score: hazard ratio, 1.6 95% confidence interval, 1.1-2.3; CES-D score increase: hazard ratio, 1.5 95% confidence interval, 1.1-2.2; and persistently high symptoms: hazard ratio, 1.5 95% confidence interval, 1.1-2.3). CONCLUSION: Older adults who reported higher depressive symptoms were more likely to develop diabetes than their counterparts; this association was not fully explained by risk factors for diabetes.