Risk and protective factors of healthy cognitive ageing across diverse global cohorts and causal effect of education

The global rise in cognitive impairment calls for preventive strategies through early identification of risk and protective factors in the community healthy elderlies that take into account cultural and geographic diversity. This study investigates how risk and protective factors influence cognitive functioning and depressive symptoms of older adults across six diverse cohorts (n=1,636) from Europe, Asia, and Australia. We found that younger age at baseline and longer education covary with better baseline cognitive function, with a marginal average effect of education beyond individual, geographical, and birth cohort differences. Harnessing multimodal brain MRI, we find that this relationship is mediated by normalised grey matter, with a statistically significant pooled effect across cohorts. Using a natural experiment, we then establish the causal effect of education on cognition six decades later. By including underrepresented populations and by generalising findings, this research extends the evidence base beyond dominant Western-focused research norms, underscoring a call for inclusive and equitable access to education to enhance lifelong cognitive trajectories.