Additional education protects people with high genetic risk of dementia

A law that required British teenagers to stay in school for an additional year had an unexpected consequence nearly 50 years later: fewer dementia diagnoses.

Researchers at the University of Southern California, the University of Wisconsin–Madison and the University of Michigan studied a 1972 British compulsory-schooling reform that raised the minimum school-leaving age from 15 to 16. They found that the additional education resulting from the reform reduced diagnoses of Alzheimer's disease and related dementias decades later.

The new study also uncovered a striking second finding: the reduction in dementia incidence happened even among people with high genetic susceptibility to the disease. The results suggest that education may be particularly protective for those at greatest inherited risk, challenging the idea that genetic risk is an unchangeable forecast of future health.

The study is believed to be the first to document a causal relationship between education and diagnosed dementia and to show that education can mitigate inherited risk of dementia. It was published in the Proceedings of the National Academy of Sciences.

A policy change that helps separate cause from correlation

People with more education have long been known to face lower dementia risk. But that pattern alone does not establish whether schooling causes the difference. For example, people with more education may have grown up in different family and socioeconomic circumstances that also influence their health later in life.

The researchers addressed that problem by studying a 1972 reform in England, Scotland and Wales that raised the minimum school-leaving age from 15 to 16. Students born on or after September 1, 1957, had to stay longer; those born just before the cutoff could still leave at 15.

That sharp dividing line allowed the researchers to compare people born only days apart who faced different schooling requirements but were otherwise highly comparable. The reform increased the share staying in school until at least age 16 by 14 percentage points. 

Using UK Biobank data, the researchers followed participants through age 65 using hospital records, death registries and self-reported medical history. Those born just after the cutoff-and therefore required to stay in school longer-were less likely to be diagnosed with dementia than those born just before it.

The study's design moves beyond the familiar association between education and better health: it provides evidence that the additional schooling induced by the reform caused a reduction in dementia incidence. 

"We have known for a long time that people with more education are less likely to develop dementia, but it has been difficult to know whether education itself is responsible," said lead author Silvia Barcellos, a health economist who is affiliated with the Center for Economic and Social Research at the USC Schaeffer Institute and the University of Wisconsin–Madison. "By taking advantage of this school reform, we can separate the effect of education from many of the other factors that differ across people. Our findings provide evidence that education itself can reduce dementia risk decades later."

Education matters even for those at highest genetic risk

The researchers then combined the schooling reform with genetic data to ask another critical question: Could additional education protect people born with a high genetic susceptibility to dementia?

They found the additional schooling reduced dementia incidence even among people at the highest genetic risk. The results suggest that genetic predisposition is not destiny: the conditions in which people live and learn can influence whether someone at higher risk develops the disease.

The findings broaden the conversation about dementia prevention beyond interventions that begin late in life. They suggest that investments made decades before symptoms emerge-including investments in education-may influence dementia risk much later in life.

For people who know they have a higher genetic risk of dementia, this is a hopeful finding. Genes help shape disease risk, but they do not necessarily determine the outcome. Our results suggest that experiences and circumstances that can be changed over the course of life may influence whether inherited susceptibility ultimately translates into disease. Understanding which interventions can produce these protective effects is an important direction for future research."

Leandro Carvalho, coauthor, associate professor of economics at USC

How schooling could shape brain health

More schooling could influence dementia through better job opportunities, higher income, more cognitively stimulating work, and changes in health and social circumstances. In the study, additional schooling also increased household income and reduced the incidence of stroke and heart attack. However, the researchers could not determine which mechanisms accounted for the reduction in dementia. 

The researchers emphasized it is less clear by how much additional schooling reduces dementia risk. Because dementia was still uncommon in this relatively young group, the estimates are imprecise. Following participants as they age will show whether the reductions persist as dementia becomes more common.