You probably know someone who worries about dementia because it runs in the family.
Many of us treat that risk as fixed, written into our DNA. New research pushes back on that idea.
Staying in school one extra year appears to have measurably lowered dementia diagnoses decades later. The effect held even among people carrying the genes that raise the risk most.
The finding was published in late October 2026 in the Proceedings of the National Academy of Sciences.
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Researchers used a 1972 British school reform as a natural experiment. The reform raised the minimum school-leaving age from 15 to 16, but only for students born after September 1, 1957. People born just days apart ended up facing different rules.
Teams at USC, the University of Wisconsin-Madison and the University of Michigan tracked more than 100,000 UK Biobank participants through age 65. They pulled dementia diagnoses from hospital records, death registries and self-reported medical history.
How much the extra year moved the needle
The reform pushed roughly 14 percentage points more students to stay in school until 16. Over the following five decades, that extra year was linked to a small drop in new dementia cases.
The researchers describe the estimate as imprecise, because dementia is still uncommon before age 65.
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According to the USC Schaeffer Institute, the extra schooling also raised household income and lowered the incidence of stroke and heart attack.
Where the signal was strongest
The protective effect was most visible in people whose genes placed them at the highest risk of Alzheimer's disease and related dementias. In this group, the reform appeared to weaken the link between those genetic markers and later diagnoses.
"We have known for a long time that people with more education are less likely to develop dementia," lead author Silvia Barcellos said in the USC Schaeffer announcement. "But it has been difficult to know whether education itself is responsible."
Barcellos is a health economist at USC and the University of Wisconsin-Madison.
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She framed the natural experiment as a way to separate education from the many other factors that differ with schooling.
Co-author Leandro Carvalho, an economist at USC, called the pattern a hopeful signal for people with a family history of dementia. Genes help shape disease risk, he added, but do not necessarily decide the outcome.
The oldest UK Biobank participants in this cohort turned 65 by December 2022, which is still young for dementia. Longer follow-up as the group moves into their 70s and 80s may sharpen the estimate.
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This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.