Neuropathological Correlates of Apathy Progression in Alzheimer's Disease and Related Dementias: A Longitudinal NACC Cohort Study

ObjectiveApathy is a prevalent and disabling symptom in Alzheimers disease and related dementias, yet its progression across neuropathological subtypes remains incompletely understood. This cohort study investigates longitudinal changes in apathy and their associations with major neuropathologies using data from the National Alzheimers Coordinating Center. MethodsWe analyzed 1,488 participants with autopsy-confirmed neuropathology and at least two caregiver-reported NPI-Q assessments. Generalized linear mixed models were used to assess associations between apathy and six neuropathologies--Alzheimers disease (AD), Lewy body disease (LBD), frontotemporal lobar degeneration (FTLD), hippocampal sclerosis (HS), cerebrovascular disease (CVD), and cerebral amyloid angiopathy (CAA). with time modeled as years to death and including interaction terms. Sex-stratified analyses were also conducted. All models were adjusted for age at death, sex, and NPI-Q total score excluding apathy. ResultsApathy prevalence increased over time across all pathology groups. FTLD (OR = 2.11, 95% CI: 1.32-3.39) and HS (OR = 2.23, 95% CI: 1.38-3.60) were consistently associated with higher odds of apathy throughout the disease course. No significant interaction effect was observed in any of the neuropathologies. In sex-stratified analyses, FTLD (OR=2.58, 95% CI 1.40-4.77), HS (OR=2.48, 95% CI 1.29-4.77), and LBD (OR=1.64, 95% CI 1.03-2.61) were significantly associated with apathy in males, while only HS (OR=2.18, 95% CI 1.06-4.47) remained significant in females. InterpretationApathy severity varied by neuropathologies but progressed similarly over time. The elevated burden in FTLD and HS, particularly among males, underscores the importance of stratified approaches to early detection and intervention targeting apathy in ADRDs.