One extra year of secondary school links to lower dementia incidence 50 years later

An NIH-funded study used Britain's 1972 reform that raised the minimum school-leaving age from 15 to 16 to compare people born just before and after the policy boundary. The reform increased the share staying in school until 16 by 14%. Researchers analyzed medical histories, hospital records and death registries from more than 100,000 UK Biobank participants and linked the extra year of education to a 0.88-percentage-point reduction in Alzheimer's disease and related dementia incidence over roughly the next 50 years. The signal was strongest among people carrying variants associated with higher genetic risk. A natural experiment supports stronger causal inference than a standard observational study, but limits remain: the oldest participants were only 65 at the main comparison, dementia rates were low, and the difference may grow or shrink as the cohort ages. Education does not erase inherited risk; the result shows that social policy may alter long-term brain-health trajectories.