Association of Alzheimer's disease biomarkers with malnutrition and altered body composition in cognitively impaired patients: a cross-sectional memory clinic study.

INTRODUCTION: Alzheimer’s disease (AD) is marked by early weight loss, with unclear underlying mechanisms. Using real-world data, we aimed to investigate the links between biological AD profile, body composition, and nutritional status in patients with cognitive impairment. METHODS: Cross-sectional study of patients with cognitive decline who underwent cerebrospinal fluid (CSF) AD biomarkers and bioelectrical impedance analysis. Nutritional status was assessed using Global Leadership Initiative on Malnutrition (GLIM) criteria. Analyses were stratified by sex and adjusted for age, MMSE, comorbidities, and the presence of a caregiver at home. RESULTS: Among 420 patients, 31.7% suffered from malnutrition which was associated with older age (p = .003), social isolation (p = .004), and lower MMSE scores (p = .010). Malnutrition was associated with higher pTau-181 (p = .018) and t-tau (p = .018) in women after adjustment for confounding factors. Lower Aβ42/40 ratio was associated with lower fat mass index in men (p < .001), whereas higher pTau-181 and t-tau were associated with lower fat mass index in women (p = .024 and p = .018). CONCLUSION: These results highlight the high prevalence of malnutrition in patients with cognitive disease from memory centers, and the association of AD CSF biomarkers with malnutrition and lower fat mass. Additional longitudinal and animal studies are needed to unravel this potential pathophysiological link. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13195-026-01965-1.