Education reduces dementia incidence and mitigates genetic risk.

There is little causal evidence on factors that can protect individuals against Alzheimer's Disease and Related Dementias (ADRD) risk. We study the causal effect of education on ADRD, exploiting a regression discontinuity generated by a compulsory schooling reform. ADRD was ascertained based on medical history, hospital records, and death registries, addressing concerns about selective sample attrition. We find that education reduces incidence of ADRD. Using molecular genetic data, we show that the reform weakened the relationship between genetics and ADRD incidence, implying genetic risk of dementia is not immutable and can be modified by social policy.