Symptom Dimensions of Depression and 3-Year Incidence of Dementia

Abstract

Objective: To evaluate the association between depressive symptom dimensions and incident dementia in a community sample of older persons. Methods: Depressive symptoms at baseline and incident dementia at 3-year follow-up were assessed with the Geriatric Mental State (GMS)–Automated Geriatric Examination for Computer Assisted Taxonomy in nondemented persons aged 65 years or older. Exploratory and confirmatory bifactor analysis on the depression items yielded a general depression factor characterized by all GMS items and a cognitive/motivational factor characterized by cognitive and motivational “depressive” symptoms and the absence of depressed mood. Results: Ninety-three of 1911 persons had developed dementia at follow-up. The general depression factor increased the risk of dementia after adjustment for covariates (odds ratio [OR]: 1.48, 95% confidence interval [CI]: 1.14-1.92), but the cognitive/motivational factor did not (OR: 1.05, 95% CI: 0.75-1.47). However, in 1725 nondepressed older persons, the cognitive/motivational factor significantly predicted dementia after adjustment for covariates (OR: 1.53, 95% CI: 1.03-2.28) but not anymore after additional adjustment for subjective memory complaints (OR: 1.41, 95% CI: 0.94-2.13). The general depression factor did not significantly predict dementia in nondepressed older persons (OR: 1.15, 95% CI: 0.80-1.66). Conclusion: Our findings suggest that the increased risk of dementia associated with depressive symptoms in many previous studies appears to be heterogeneous, that is, it is likely due to different underlying pathways, including a pathway involving depression itself and a pathway in which cognitive and motivational symptoms reflect subjective cognitive complaints, particularly in the absence of depressed mood. These different pathways might warrant a different treatment approach.