An extra compulsory year of school in the UK was followed by fewer dementia diagnoses decades later, study finds

A study published on 23 October 2026 in PNAS and funded by the US National Institutes of Health offers what the NIH calls perhaps the strongest evidence yet that education can reduce long-term dementia risk. It was led by researchers at the University of Wisconsin–Madison and the University of Southern California.

The natural experiment

A UK reform raised the minimum school-leaving age from 15 to 16 for pupils born after 1 September 1957, increasing the share who stayed in school until 16 by 14%. Because birth date alone decided who was affected, comparing people born just before and after the cut-off works much like a natural experiment. The team analysed records of more than 100,000 participants in the UK Biobank, drawing diagnoses from medical histories, hospital records and death registries.

Findings

• According to the NIH, the extra year of schooling reduced Alzheimer’s disease and related dementias over the following 50 years by 0.88% — a sizeable effect given that dementia rates in this relatively young group were low.
• The effect was strongest among people carrying genetic variants that raise dementia risk.
• The reform was also linked to better socioeconomic and other health outcomes, hinting at possible pathways.

Limitations

The main comparison used diagnoses made before December 2022, when the oldest participants turned 65 — before most dementia appears. The authors caution that differences between groups may grow or shrink as the cohort ages. UK Biobank volunteers are also healthier and wealthier than the general population, and results from one British reform may not transfer to other countries.