A school-age law from 1972 offers a natural test of education and dementia

A PNAS study finds one extra school year in Britain may have cut dementia incidence, though the authors say the size of the effect is unreliable.

A study in PNAS, led by health economist Silvia Barcellos of the University of Wisconsin-Madison with Leandro Carvalho of the University of Southern California, asks whether more schooling lowers the risk of dementia. It uses a policy accident. The 1972 Raising of School-Leaving Age Act lifted the minimum leaving age from 15 to 16 in England, Scotland and Wales, but only for students born after 1 September 1957.

That birth-date cutoff works as a natural experiment. The researchers compared people born just after it, who had to stay until 16 and are now in their late sixties, with people born just before it, who could leave at 15. Using UK Biobank data, they found that cumulative incidence of Alzheimer's Disease and Related Dementias dropped sharply among those born after the cutoff. The estimated effect of the extra year was about 0.88 percentage points. DNA data let them split participants by genetic risk, including APOE4 variants. The extra year was linked to a significant reduction in the high-risk group.

For abundance, this matters because schooling is one of the cheapest levers a society controls, and the study suggests it may also act on health decades later. The authors call it the first causal evidence of its kind. They propose that the benefit may run through higher qualifications, income and occupational status.

The caveats are large. Overall prevalence in the sample was under 1 percent, so the authors themselves call the 0.88-point figure implausibly large and suggest statistical factors. They say they can credibly estimate the direction of the effect, not its precise size. The mechanism is unknown, and the findings come from unusual UK circumstances. Watch for follow-up in older cohorts, where more dementia cases will allow more precise estimates.

Source: ScienceAlert