Abstract
This study examines associations between blood-based neurodegenerative biomarkers and cognitive functioning in nationally representative samples of older adults in India and the United States. Using data from the Longitudinal Aging Study in India-Diagnostic Assessment of Dementia (LASI-DAD) and the Health and Retirement Study (HRS), we analyzed four biomarkers-the ratio of Amyloid beta 42 to 40 (Aβ42/Aβ40), Glial Fibrillary Acidic Protein (GFAP), Neurofilament Light Chain (NfL), and Phosphorylated Tau at Threonine 181 (pTau181)-in relation to cognitive outcomes. Higher levels of GFAP and NfL were associated with worse cognitive function and a greater likelihood of dementia in both populations. GFAP and NfL also were associated with cognitive decline in the HRS, but not in LASI-DAD. Higher Aβ42/Aβ40 ratio was associated with worse cognitive functioning and more dementia in HRS; on the other hand, higher levels of the Aβ42/Aβ40 ratio were significantly linked with better cognitive functioning in LASI-DAD. PTau181 was generally not associated with cognitive functioning in either country. These findings suggest some promise for these biomarkers, especially GFAP and NfL, for clarifying associations with cognitive decline and dementia. The associations of the whole set of markers with subsequent mortality suggest they may serve as markers for general aging.