Apathy, depression and risk of incident dementia in community‐dwelling older adults

Abstract

AbstractBackgroundApathy, which may be a risk or prognostic factor for incident dementia in older adults, has been little investigated in cognitively normal populations and has largely lacked consideration of comorbid depression. Understanding the potential role of apathy in the development of dementia has also been limited by short follow‐up periods, and cohorts with restricted age ranges (below 80 years). Our aim was to investigate whether self‐report apathy predicted incident dementia over 14 years, when adjusting for comorbid depression in a population‐based sample of older adults (aged 70‐90) without dementia at baseline.MethodThe Sydney Memory and Ageing Study included 1,037 community‐dwelling participants at baseline (median age 78 years (range 70‐90); 55% female). Assessments included the self‐report Geriatric Depression Scale, from which apathy (GDS‐3A) and depression (GDS‐12D) subscores were obtained. Incident dementia was diagnosed by expert panel clinical consensus at biennial assessments for up to 14 years. Cox survival analyses examined risk conferred by apathy and depression for incident dementia separately, and then included both in the same model as concurrent predictors. Analyses were initially unadjusted. The fully adjusted model controlled for baseline age, sex, education, non‐English speaking background, global cognition (MMSE), APOE4 status and health conditions.ResultOf the 858 participants with follow‐up data, 271 developed dementia (31.6%), over an average 9 years follow‐up. Self‐report apathy and depression separately predicted higher risk for dementia in the unadjusted models (hazard ratio [HR] 1.45, 95% confidence interval [CI] 1.05, 2.00; HR 1.47, 95% CI 1.06, 2.04, respectively). When including both apathy and depression concurrently in the model, apathy remained a significant risk factor, but depression did not. In the fully adjusted model, apathy no longer significantly predicted incident dementia. Post‐hoc analyses using split‐half groups by age showed the effect was attenuated only for younger participants (below 78 years).ConclusionApathy was associated with increased risk of incident dementia, independently of depression, over 14 years in a community‐dwelling population‐based cohort of older adults. This novel evidence of long‐term risk addresses prior limitations in the literature and implicates apathy as a prognostic marker for dementia, particularly with increasing age.