An extra year of required secondary school cut later dementia diagnoses by about .88% over 50 years, according to an NIH-funded study in the Proceedings of the National Academy of Sciences.

NIH said Friday that researchers at the University of Wisconsin-Madison and the University of Southern California led the work. A UK rule raised the youngest age for leaving school from 15 to 16 for students born after September 1, 1957. That change raised by 14% the share of students who stayed until age 16, NIH said.

The team studied medical data from more than 100,000 people in the UK Biobank. Diagnoses before December 2022, when the oldest people in the group turned 65, were the main test. Researchers used medical histories, hospital records and death registries, NIH said.

The .88% drop was large given low dementia rates in the sample, NIH reported. The signal was strongest for people with gene variants that raise Alzheimer's and related dementia risk. Lead author Silvia Barcellos of UW-Madison said the point is less about the exact number and more about how school ties to dementia risk, according to NIH.

National Institute on Aging Director Richard Hodes said the findings show dementia risk rests on more than genes, and that added school years can offset inherited risk, according to NIH. Authors warned that the age cap at 65 limits how far the results can be read. As the group ages, the gap may grow or shrink, NIH said.

The study also linked the reform to better money and health outcomes that may help explain the dementia effect, NIH reported. NIH funded the work through National Institute on Aging grants. An NBER working paper by the same authors shares the research for comment.

What we know: An extra year of school tied to a UK reform was linked to fewer dementia diagnoses over 50 years, with a bigger effect at high genetic risk.
What we don't: How large the effect will look once more of the group ages past 65.