Geographic Heterogeneity in the Association Between Schooling and Cognitive Change Among Older Adults in India

Higher educational attainment is associated with steeper measured cognitive decline among older adults in India, but whether this association is uniform across the country is unknown. Using the Harmonized Diagnostic Assessment of Dementia for the Longitudinal Aging Study in India (wave 1, 2017-2019; wave 2, 2022-2024), this study examined whether the association between years of schooling and cognitive change varied across 18 states and union territories among 2,510 adults aged 60 years or older who were assessed at both waves. Models adjusted for age, sex, household wealth, and rural or urban residence. Change-score models related inter-wave change to schooling, and analysis of covariance additionally conditioned on baseline cognition. The schooling-by-geography interaction was significant in both specifications (change score, F = 2.97, P < .001; analysis of covariance, F = 4.11, P < .001). State-specific change-score estimates ranged from -0.056 SD per year of schooling in Odisha to +0.021 SD in Kerala. The pooled association reversed sign with baseline adjustment, from -0.022 SD (95% CI: -0.027, -0.016) to +0.031 SD (95% CI: 0.024, 0.038). A single national coefficient conceals substantial geographic variation in how schooling relates to cognitive aging in India.