HISTORY OF DEPRESSION AS A RISK FACTOR FOR ALZHEIMERS-DISEASE

Research regarding the possible association between Alzheimer's diseas e and a history of depression has been inconclusive. Using a case-cont rol design, we assessed the strength of the association between report ed history of depression and onset of Alzheimer's disease. We enrolled probable Alzheimer's disease cases (N = 294), who were ascertained an d diagnosed by our Alzheimer's Disease Patient Registry, and randomly selected nondemented controls (N = 300) of similar age and gender from the same base population. The mean age (for cases) was 78.5 years. In formants provided data regarding history of depression. ''Treated depr ession'' was defined as depression for which a physician/psychologist consultation, medication, or hospitalization had occurred. Restricting treated depression to exclude primary loss or grief reactions, we fou nd a modest association with Alzheimer's disease [odds ratio (OR) = 1. 8; 95% confidence interval (CI) = 0.9-3.5] after adjusting for gender, age, education, and type of informant, When these data were stratifie d by depression onset year, we observed an odds ratio of 2.0 (95% CI = 0.9-4.6) for depression occurring more than 10 years before the onset of dementia symptoms, and an OR of 0.9 (95% CI = 0.2-3.0) for depress ion onset within 10 years of the onset of dementia symptoms. Thus, dep ressive episodes occurring well before dementia symptom onset appear t o increase the risk of Alzheimer's disease.