Factors Associated with Apathy in Alzheimer's Disease: A Cross-Sectional Analysis of the Texas Alzheimer's Research and Care Consortium (TARCC) Study

Background: Apathy is among the most frequent neuropsychiatric syndromes in Alzheimer's disease (AD). Objective: To determine the prevalence of apathy and the associated clinical and laboratorial parameters (focus on inflammatory biomarkers) in patients with dementia enrolled at the Texas Alzheimer's Research and Care Consortium (TARCC) study. Methods: This is a cross-sectional analysis of TARCC baseline. Participants were evaluated through different clinical tools, including the Mini-Mental State Examination (MMSE) and the Lawton-Brody Instrumental Activities of Daily Life (IADL)/Physical Self-Maintenance Scale (PSMS). Apathy was defined by a positive response to the respective item in the Neuropsychiatric Inventory-Questionnaire applied to caregivers. Serum levels of 16 biomarkers were determined by HumanMap multiplex immunoassay. Comparisons between apathy versus non-apathy groups were carried out with non-parametric tests. Logistic regression and the least absolute shrinkage and selection operator (LASSO) were used to separately model apathy as a function of each biomarker, adjusted for the potential confounders. Results: From 1,319 patients with AD (M/F: 579/740, mean age±SD: 75.3±8.4), 373 (28.3%) exhibited apathy. When categorized according to the presence of apathy, the groups had significant differences in sex, diabetes diagnosis, and tobacco use. The apathy group also had worse cognitive performance and daily functioning than the non-apathy group as assessed, respectively, by MMSE and IADL/PSMS. Higher levels of interleukin-6, interleukin-10, and leptin were associated with higher odds of apathy. Conclusion: Apathy is associated with cognitive and functional status in AD. The association between apathy and peripheral inflammatory mediators deserves further investigation.