Apathy and risk of probable incident dementia among community-dwelling older adults

Abstract

Objective: To evaluate the association between baseline apathy and probable incident dementia in a population-based sample of community-dwelling older adults.

Methods: We studied 2,018 white and black community-dwelling older adults from the Health, Aging, and Body Composition (Health ABC) study. We measured apathy at year 6 (our study baseline) with the modified Apathy Evaluation Scale and divided participants into tertiles based on low, moderate, or severe apathy symptoms. Incident dementia was ascertained over 9 years by dementia medication use, hospital records, or clinically relevant cognitive decline on global cognition. We examined the association between apathy and probable incident dementia using a Cox proportional hazards model adjusting for demographics, cardiovascular risk factors, APOE4 status, and depressed mood. We also evaluated the association between the apathy group and cognitive change (as measured by the modified Mini-Mental State Examination and Digit Symbol Substitution Test over 5 years) using linear mixed effects models.

Results: Over 9 years of follow-up, 381 participants developed probable dementia. Severe apathy was associated with an increased risk of dementia compared to low apathy (25% vs 14%) in unadjusted (hazard ratio [HR] 1.9, 95% confidence interval [CI] 1.5-2.5) and adjusted models (HR 1.7, 95% CI 1.3-2.2). Greater apathy was associated with worse cognitive score at baseline, but not rate of change over time.

Conclusion: In a diverse cohort of community-dwelling adults, apathy was associated with increased risk of developing probable dementia. This study provides novel evidence for apathy as a prodrome of dementia.

Figure 1. Association between apathy and incident dementia among 2,018 older adults

Kaplan-Meier curves show dementia incidence over 9 years by apathy tertile (p < 0.0001 by log-rank test).

Figure 2. Modified Mini-Mental State Examination (3MS) and Digit Symbol Substitution Test (DSST) over time by apathy tertile, implied by linear mixed effects model

(A) 3MS. (B) DSST. Models included demographics, education, history of myocardial infarction, history of stroke, hypertension, cigarette smoking, APOE4, and depressed mood.