The temporal relationship between depressive symptoms and dementia -: A community-based prospective study

Background: The temporal relationship between the appearance of depressive symptoms and the clinical onset of dementia and Alzheimer disease was evaluated in a community sample. Methods: An original sample of 1366 subjects aged 65 years or older, selected randomly from a rural Pennsylvania community, was cognitively screened at study entry and every 2 years thereafter. A subset of 954 survivors of this cohort without dementia was screened for depressive symptoms at the second and subsequent data-collection waves. A "depression cluster" was identified by the presence of 5 or more depressive symptoms, including depressed mood, at the time of screening. Cognitively impaired subjects and a sample of unimpaired controls underwent standardized clinical evaluation to determine the presence of incident dementia (by DSM-III-R criteria) and probable or possible Alzheimer disease (by criteria of the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association) and to estimate the clinical onset of dementia symptoms. Results: A highly increased probability of the depression cluster developing existedamong subjects following the onset of dementia (15.4% [6/39]) and Alzheimer disease (17.6% [6/34]) compared with subjects without dementia (3.2% [23/712]). The odds ratios, after adjustment for age, sex, education level, and self-reported memory loss, for the development of depression were 6.5 (95% confidence interval, 2.2-19.1) in subjects with Alzheimer disease and 5.2 (95% confidence interval, 1.8-15.2) in subjects with overall dementia. Depressive symptoms did not confer a significantly increased relative risk of dementia (1.27; 95% confidence interval, 0.55-2.93) or Alzheimer disease (1.28; 95% confidence interval, 0.51-3.20). Conclusion: Depressive symptoms appeared to be early manifestations, rather than predictors, of Alzheimer disease in this community sample.