A 1972 school law had an unexpected effect on dementia 50 years later

Staying in school for an extra year during adolescence appears to lower a person’s likelihood of developing dementia decades later, even among individuals who carry a strong inherited predisposition to the condition. Taking advantage of a 1972 British law that raised the minimum school-leaving age from 15 to 16, researchers found that the additional mandated schooling reduced early dementia diagnoses and narrowed the gap between people at high and low genetic risk. The findings, published in PNAS, suggest that educational policies can modify genetic vulnerabilities to neurodegenerative disease.

Dementia is an umbrella term for neurodegenerative conditions characterized by a progressive decline in memory, reasoning, and the ability to perform everyday activities, with Alzheimer’s disease accounting for the majority of cases. As global life expectancy rises, the number of people living with Alzheimer’s disease and related dementias is projected to surpass 130 million by 2050. Because few medical treatments can halt this decline, public health researchers have sought to identify modifiable life experiences that might delay or prevent the onset of the illness.

Formal education has drawn wide interest as a candidate, though a 2011 systematic review of 71 studies found that just over half of the populations studied showed higher dementia risk among people with less schooling. Observational studies also struggle to separate the actual impact of classroom instruction from confounding factors like childhood poverty, early-life health, or inherited traits that influence both academic achievement and brain aging.

Questions also remain about how education shapes the aging brain. An earlier analysis of memory and brain volume across adulthood found that higher education was linked to better baseline memory and larger brain size, but not to a slower pace of normal age-related memory decline or brain shrinkage, which are distinct from clinical diagnoses of dementia.

To test whether schooling directly protects against clinical dementia, researchers have turned to compulsory schooling laws that require entire generations to stay in school longer regardless of their family background. When a 2020 study of 1.3 million Swedish adults examined a reform that added an extra year of mandatory grade school, the authors found almost no effect on later dementia diagnoses, though that reform also had limited effects on adult earnings. By contrast, a 2018 study by three of the same authors behind the new paper, analyzing the same UK Biobank dataset, showed that a 1972 British secondary-school reform narrowed the gap in unhealthy body size between people at high and low genetic risk of obesity.

That earlier work raised the question of whether educational policy could similarly counteract the genetic risk for dementia, a condition whose heritability in twin studies is estimated to be as high as 80 percent. The new research, led by Silvia Helena Barcellos, an associate professor of population health sciences and public affairs at the University of Wisconsin-Madison and a research associate at the National Bureau of Economic Research, combined genetic profiles with national medical records to test whether the 1972 British schooling reform reduced clinical dementia diagnoses and blunted inherited susceptibility.

“We wanted to understand whether education actually protects against dementia and whether it can reduce the risk associated with genetic predisposition to the disease,” Barcellos told PsyPost. “This is important because it guides potential policies and interventions that might be able to reduce the burden of this terrible disease.”

The team analyzed data from the UK Biobank, a large health study that recruited more than 500,000 British adults between the ages of 40 and 69 from 2006 to 2010. Rather than relying solely on follow-up surveys, where participants developing memory problems frequently drop out, the authors tracked dementia diagnoses through December 2022 using linked national hospital records, death registries, and medical histories. Prior validation testing in this database indicates that at least 84.5 percent of dementia cases identified through these administrative records are true positives.

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To isolate the causal effect of education, the researchers examined a natural experiment created by the 1972 Raising of School-Leaving Age Act in England, Scotland, and Wales, which increased the minimum age for leaving school from 15 to 16. Because of the school-year cutoff, teenagers born on or before August 31, 1957, could legally drop out at age 15, whereas those born on or after September 1, 1957, had to remain until at least age 16.

The authors used a statistical method called a regression discontinuity design, which compares people born within a few years on either side of that September 1, 1957 threshold. Participants born just before and just after that date had similar genetic risk scores and had parents with similar rates of dementia, so any abrupt shift right at the cutoff can be credited to the mandated schooling. Depending on the specific analysis and birth-date window around the cutoff, the working sample included between 25,738 and 112,752 participants who were born in England, Scotland, or Wales, or who had immigrated to the United Kingdom by age 14.

For the genetic analyses, the researchers examined participants of European genetic ancestry and built a polygenic index, a composite score summarizing each person’s inherited predisposition to dementia based on a large prior genome-wide association study. This score combined a very large number of common single-letter DNA variations with variants of the apolipoprotein E gene, known as APOE, where carrying the high-risk APOE4 version substantially elevates Alzheimer’s risk. Because APOE has such a strong influence on dementia, being in the top half of the genetic risk distribution largely meant carrying the APOE4 variant: 58 percent of the high-risk group had at least one APOE4 copy, compared to 0.02 percent of the low-risk group.

The 1972 reform increased the share of students who stayed in school until age 16 by 14 percentage points, adding an average of 0.19 years of schooling. By December 2022, when the first affected cohort turned 65, 0.49 percent of those born before the cutoff had a dementia diagnosis. Those born under the reform were 0.20 percentage points less likely to have one, with similar declines for men and women.

When the researchers scaled these figures to estimate the effect of a full additional year of schooling among participants who left school at age 18 or younger, they calculated a reduction of 0.88 percentage points in dementia incidence. Because the cohort was only around 65 at the end of 2022, just 0.61 percent of that subgroup born before the cutoff had a dementia diagnosis, so the authors acknowledge that a 0.88-point reduction is implausibly large. The authors note that estimating rare outcomes at a cutoff involves substantial sampling variation, with a range of plausible values (the 95 percent confidence interval) spanning from a 0.15 to a 1.76 percentage point reduction. Although the data cannot pinpoint the exact magnitude, those statistical bounds rule out reductions smaller than 24 percent of the baseline rate.

“However, I would caution against focusing too much on the precise size of the effect,” Barcellos explained, noting that dementia remains uncommon among people 65 and younger. “What gives us confidence is the research design, which provides evidence that education itself, rather than simply other characteristics of more educated people, can reduce dementia incidence. As these individuals grow older, we will be able to estimate the magnitude of the effects more precisely.”

Next, the authors compared participants in the top and bottom halves of the genetic risk distribution, where the 1972 law increased the rate of staying in school until age 16 by 14 percentage points in both groups alike. Among people born before the September 1, 1957 cutoff, those in the high genetic risk group had a dementia incidence rate 0.18 percentage points higher than those in the low genetic risk group, a gap that shrank to 0.02 percentage points among those born after the cutoff.

In the regression models, the estimated drop in dementia was roughly twice as large in the high genetic risk group as in the low-risk group, and only the high-risk group’s estimate reached statistical significance, though only narrowly. The formal test comparing the two groups was not statistically significant, which the authors suggest may reflect limited statistical power.

“One of the most striking findings was that education appeared to weaken the relationship between genetic predisposition and dementia,” Barcellos said. “People with higher genetic risk seemed to benefit particularly strongly from the additional schooling. This is especially interesting because genetic risk is often thought of as something fixed. While we cannot change the genes we inherit, our findings suggest that the consequences of those genes can be influenced by our environments and experiences.”

“I think this is a hopeful message: our genes do not necessarily determine our destiny,” she added. “Even for diseases like Alzheimer’s, where genetics can play an important role, experiences and circumstances that can be changed, such as education, may influence whether someone develops the disease.”

The finding that extended schooling may protect against dementia aligns with an earlier study of older adults taking college courses, which found that 92 percent of seniors who completed at least a year of university classes showed gains in cognitive capacity compared to 56 percent of a control group. However, that earlier research examined short-term cognitive test gains from late-life coursework rather than clinical dementia diagnoses decades after secondary school.

Similarly, the evidence that education can buffer inherited susceptibility is consistent with a study of middle-aged adults indicating that intellectually stimulating hobbies like travel and music were associated with better cognitive performance in people at high genetic risk for Alzheimer’s disease. That work evaluated midlife activities and thinking tests in healthy adults rather than mandatory adolescent schooling and clinical diagnoses.

To explore how staying in school until age 16 might translate into fewer dementia diagnoses half a century later, the researchers examined whether the reform shifted midlife household income and medical conditions tied to brain health. Because the 1972 law provides only a single source of policy variation, the authors caution that their analysis cannot quantify how much any specific pathway contributed to the drop in dementia, only whether the policy affected those intermediate outcomes.

Participants born under the school reform were 2.3 percentage points more likely to have an annual household income of at least 31,000 pounds and 0.64 percentage points less likely to have suffered a stroke or heart attack, with the reduction in strokes and heart attacks concentrated in the high genetic risk group. Reductions in diabetes and obesity were not statistically significant, and those affected by the reform were also more likely to develop stage 1 high blood pressure.

There are a few things to keep in mind when interpreting these results, starting with the relatively young age of the people studied. The first cohort affected by the 1972 school reform had only reached age 65 by the end of the study’s follow-up period in December 2022, an age when fewer than 1 percent of participants had been diagnosed with dementia. Because dementia is uncommon at that age, the estimates carry wide margins of error. The Swedish study, which found no effect, followed participants until ages 79 to 96, so researchers will need to keep tracking the British cohort into later life to see whether the protective effect persists.

“We do not yet know whether the additional education will prevent dementia altogether or whether it may primarily delay its onset,” Barcellos noted. “Both possibilities are important, but distinguishing between them will require following these individuals as they age.”

In addition, the findings reflect the specific historical context of keeping 15-year-old British students in school for one additional year during the 1970s. Earlier work by the same team found that staying until 16 led to more school qualifications, higher income, and better jobs. The authors propose this may explain why the British reform lowered dementia rates while the earlier Swedish schooling reform, which had limited effects on income, showed no measurable impact. Consequently, these findings apply to basic secondary education among students who would have otherwise dropped out early, and do not establish whether extra years of college or graduate school would yield similar protection.

“One important caveat is that our study examines the effects of additional schooling during adolescence, not the effects of returning to school later in life,” Barcellos said. “We therefore cannot conclude that taking additional classes as an adult would have the same protective effect, although lifelong learning may have other benefits.”

The authors also weighed whether more educated people might simply be diagnosed less often for a given level of cognitive decline, but judged this unlikely because empirical studies indicate that educated people with clinical dementia are at least as likely to receive a formal diagnosis.

The study sample is drawn from the UK Biobank, a volunteer cohort whose participants tend to be healthier, wealthier, and better educated than the general British population. The genetic analyses were also limited to individuals of European ancestry because the underlying genome-wide studies used to calculate genetic risk scores were conducted primarily in European samples and do not transfer accurately to other populations. Future research in more socioeconomically and racially diverse cohorts will be needed to determine how broadly educational policies can buffer against inherited risks for dementia.

“We are extending this research to other countries, including Finland and the Netherlands, to understand whether the effects of education on dementia are similar across different populations and educational systems,” Barcellos said. “We also want to better understand the mechanisms behind these effects. Does education protect against dementia by improving economic opportunities, changing health behaviors, reducing cardiovascular risk, or through other pathways?”

“Another important direction of my research is understanding the economic consequences of dementia, not only for patients but also for their families,” she added. “Dementia can have profound effects on employment, income, wealth, and caregiving responsibilities. Better understanding these consequences is essential for designing policies that support individuals with dementia and their families.”

“I think our findings highlight the importance of considering education not just as an investment in economic opportunities, but also as a potential investment in long-term health,” Barcellos concluded. “Education policies implemented early in life may have consequences that extend many decades into the future. The study also illustrates how social policies can help us understand and potentially reduce health risks that are often considered largely biological or genetic.”

The study, “Education reduces dementia incidence and mitigates genetic risk,” was authored by Silvia H. Barcellos, Leandro S. Carvalho, Kenneth M. Langa, Sneha Nimmagadda, and Patrick Turley.