Association of Depression Dimensions With Cognitive Functioning in Community-Dwelling Oldest-Old Adults: The LifeAfter90 Study

OBJECTIVES: The oldest-old adults (90+) constitute the fastest-growing demographic at the highest dementia risk among older adults. Depression, a common risk factor, inherently presents with heterogeneous clinical manifestations. Here, we explored the associations of the predominant depression dimensions with cognition in the LifeAfter90 study. METHODS: The LifeAfter90 study consists of racially/ethnically diverse community-dwelling adults of >90. Cognitive assessments measured episodic memory, semantic memory, and executive function. Baseline depression was measured by the Geriatric Depression Scale-15 item (GDS-15), yielding dimensions of Dysphoria, Withdrawal-Apathy-Vigor, Anxiety, Hopelessness, and Subjective Memory Complaint (SMC). We used generalized linear mixed models to explore associations between depression dimensions, and cognitive outcomes at baseline and over time adjusting for demographic factors. RESULTS: The cohort (n = 960, mean age 92.4 ± 2.3 years, 61.56% female) was very racially and ethnically diverse with 27% of participants identifying as White, 24% as Asian, 23% as Black, and 19% as Latino. Common complaints included not identifying as "full of energy" (52.45%), preference to "stay home" (46.31%), and "dropped activity" (40.0%), and 25% reported SMC. Depression dimensions showed distinct associations with cognitive outcomes: SMC correlated with worse global cognition, executive function, and verbal episodic memory (all ps < .0001). Hopelessness was associated with worse executive function (p < .001). Over 1.2 years, baseline hopelessness showed a trend for a faster decline in episodic memory (β = -0.22; p = .035). DISCUSSION: In the oldest old, specific dimensions like SMC and hopelessness may help identify individuals at high risk for cognitive decline in this highly vulnerable population.