Exploring the association between higher education and steeper cognitive decline in a nationally representative longitudinal study in India.

Evidence on the association between education and cognitive decline is mixed. Recent systematic reviews suggest no association, but most evidence comes from high-income contexts. We used data from the Longitudinal Aging Study in India - Diagnostic Assessment of Dementia (LASI-DAD; N=3,673; 2017-2024) to estimate the association between educational attainment and cognitive decline using linear mixed effects models. We evaluated findings across a range of models and explored the roles of practice effects, selective survival, and assumptions about the underlying causal structure using supplementary analyses. Despite large differences in cognitive level (those with higher education had higher cognition in wave 1), compared to those with no education, those with less than primary school (difference of -0.03 SD units/year; 95% CI -0.04 to -0.01), primary school (-0.04; -0.06 to -0.03), middle-secondary school (-0.06; -0.07 to -0.04), and higher secondary school or above (-0.05; -0.07 to -0.03) had steeper cognitive decline after adjustment for demographic and early-life socioeconomic factors. Neither practice effects nor selective survival could explain findings, though findings were consistent with one of the two simulated causal structures. Analyses illustrate challenges in analyzing longitudinal cognitive data and showcase potential approaches to rule out methodological explanations and probe results.