Associations Between Education and Cognitive Decline Revisited: Evidence From India

TL;DR

Higher education in India is linked to faster cognitive decline in older adults, possibly due to regression to the mean.

Contribution

The study provides new evidence from India on how education affects cognitive decline, highlighting regression to the mean as a potential explanation.

Findings

Higher educational attainment is associated with steeper cognitive decline in older adults in India.

Selective survival and practice effects do not explain the observed associations.

Regression to the mean may distort findings when adjusting for education in cognitive decline studies.

Abstract

Educational attainment is consistently associated with cognitive level, but the evidence for cognitive decline is mixed, with most research suggesting no association. However, most evidence comes from high-income contexts. We used nationally representative data from the first two waves of the Longitudinal Aging Study in India – Diagnostic Assessment of Dementia (LASI-DAD) (N = 3,673) to estimate the association between educational attainment and cognitive decline using linear mixed effects models. We evaluated the consistency of findings across a range of generalized estimating equations (GEE) models with inverse probability weights to adjust for sample selection, attrition, and mortality. We further explored the role of practice effects, selective survival, and regression to the mean using a range of supplementary analyses, including simulation analysis. 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 education and up (-0.05; -0.07 to -0.03) had steeper cognitive decline after adjustment for demographic and early-life socioeconomic factors. Neither selective survival nor practice effects could explain findings. However, evidence suggested that due to the strong association between education and baseline cognition, educational attainment may act as a proxy for cognitive level and lead to regression to the mean in models adjusting for educational attainment. Regression to the mean may impact findings on the association between education and cognitive decline more broadly, particularly in contexts with larger associations between education and cognitive level.