Depressive symptoms, vascular risk factors, and Alzheimer's disease

Background Depressive symptoms in the elderly are associated with an increased Alzheimer's disease (AD) risk. We sought to determine whether the association between depressive symptoms and AD is explained by a history of vascular risk factors and stroke. Methods Five hundred and twenty-six elderly persons from New York City without dementia at baseline were followed for a mean of 5 years. Depressive symptoms were assessed using the 17-item Hamilton Depression Rating Scale (HAM). Incident AD was ascertained using standard criteria. Diabetes, hypertension, heart disease, current smoking and stroke were ascertained by self-report. Proportional hazards regression was used to relate HAM scores to incident AD. Results HAM scores were higher in persons with hypertension, heart disease, and stroke, which in turn were related to higher AD risk. AD risk increased with increasing HAM scores as a continuous logarithmically transformed variable (HR for one point increase = 1.4; 95% CI = 1.1, 1.8) and as it categorical variable (FIR for HAM >= 10 = 3.4; 95% CI = 1.5,8.1; p for trend = 0.004 with HAM = 0 as the reference). These results were virtually unchanged after adjustment for vascular risk factors and stroke, individually (HR for HAM >= 10 = 3.4; 95% CI = 1.5,8.1; p for trend = 0.004), and in a composite measure (HR for HAM >= 10 = 3.0; 95% CI = 1.2,7.8; p for trend = 0.02). Conclusion The prospective relation between depressive symptoms and AD is not explained by a history of vascular risk factors and stroke, suggesting that other mechanisms may account for this association. Copyright (c) 2008 John Wiley & Sons, Ltd.