Alzheimer's disease biomarkers as predictors of trajectories of depression and apathy in cognitively normal individuals, MCI and AD dementia.

OBJECTIVES To examine trajectories of depression and apathy over a 5-year follow-up period in (prodromal) Alzheimer's disease (AD), and to relate these trajectories to AD biomarkers. METHODS The trajectories of depression and apathy (measured with the Neuropsychiatric Inventory or its questionnaire) were separately modeled using growth mixture models for two cohorts (National Alzheimer's Coordinating Center, NACC, n = 22 760 and Alzheimer's Disease Neuroimaging Initiative, ADNI, n = 1 733). The trajectories in ADNI were associated with baseline CSF AD biomarkers (Aβ42, t-tau, and p-tau) using bias-corrected multinomial logistic regression. RESULTS Multiple classes were identified, with the largest classes having no symptoms over time. Lower Aβ42 and higher tau (ie, more AD pathology) was associated with increased probability of depression and apathy over time, compared to classes without symptoms. Lower Aβ42 (but not tau) was associated with a steep increase of apathy, whereas higher tau (but not Aβ42 ) was associated with a steep decrease of apathy. DISCUSSION The trajectories of depression and apathy in individuals on the AD spectrum are associated with AD biomarkers.