In 1972, the UK government raised the minimum school-leaver鈥檚 age from 15 to 16, with the goal of giving more students intellectual skills for modern occupations. Now, as these teens pass though their sixties, another benefit may be emerging: a lower risk of dementia. But with research from other groups muddying the waters, this relationship is far from clear-cut.
The idea that education protects against dementia isn鈥檛 new. at Columbia University in New York in the 1990s. He later credited education 鈥� along with challenging jobs and leisure activities in later life 鈥� with building our , which could make us more resilient to brain changes.
Reserve-boosting activities 鈥渟omehow allow people to cope with, or do better in the face of, age-related brain changes or pathology鈥�, says Stern.
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But despite studies finding a correlation between education and lower dementia rates, it鈥檚 hard to say whether that reasoning is correct. 鈥淚s it causal?鈥� asks at the University of Oslo, Norway. 鈥淥r is it just that people with higher education are, on average, different from those with lower education?鈥�
For instance, people who happen to have brains that are resilient against dementia may also tend to spend more time in education. Alternatively, individuals may be more educated if they are from , which has been linked to a .
In an attempt to untangle this, Fjell and his colleagues among men born in Norway in the 1950s who underwent cognitive testing aged 18 during military conscription.
Both time in education and higher cognitive scores predicted a lower incidence of dementia, but the team found it was the cognitive scores that seemed to be the ultimate driver, influencing both education and dementia risk. 鈥淎lthough we see that low education is associated with higher early dementia risk, this could be explained almost 100 per cent by 18-year-old cognitive function,鈥� says Fjell.
Building on this, his group recently analysed memory scores from more than 170,000 people aged over 50, and brain MRI scans from more than 6000 people across 33 Western countries. They found that while education correlated with better memory and a larger brain volume, which supports cognitive resilience, it didn鈥檛 ward off age-related decline.
Fjell declined to discuss the while it undergoes peer review, but the team concluded that individuals with certain early-life experiences, such as , are more likely to pursue education, and these experiences could potentially protect against dementia. 鈥淒ementia diagnosis is affected by things happening very early in life, from conception and through 18 years,鈥� he says.
These findings remain correlative, however, and constructing an experiment that randomly assigns children to receive a lengthy education or not is clearly implausible. But the 1972 reform in the UK unwittingly created a natural experiment.
鈥淧eople who are born days apart should probably be, on average, similar,鈥� says at the University of Southern California. 鈥淏ut this policy kicks in and creates a very unnatural, artificial division. It simulates a randomised experiment.鈥�
To learn more, Carvalho and his colleagues took data from roughly 100,000 participants of the UK Biobank, born four years before or after the cut-off birth date for this policy. Looking at them now, dementia cases are rare, but there was : 0.46 per cent of the group who could leave school at 15 have developed the condition versus 0.26 per cent who had to stay until 16.
鈥淚t鈥檚 a lot,鈥� says Carvalho, especially given that nearly 85 per cent of the older participants remained in education past 16.
The study also divided participants according to their genetic risk score for dementia, based on variants that influence susceptibility. The team found that before the reform, the 50 per cent of participants with the greatest genetic risk were much more likely to develop dementia than the other half. But among people made to attend school until 16, the incidence was very similar between the groups.
鈥淧eople often think about genetics as, 鈥榠t鈥檚 biological, so it鈥檚 fixed鈥�, but if you have some kind of social policy or intervention, you can change this relationship,鈥� says Carvalho.
But the team also found that those who had to stay in school until 16 had, on average, earned more and had lower rates of , which could decrease their dementia risk. 鈥淲e don鈥檛 have a good handle on the mechanisms,鈥� says Carvalho.
Something that doesn鈥檛 seem to be at play here is physically expanding the size of the brain. While it is thought that a larger brain may be able to sustain more damage before it tips over into dementia, researchers at the Radboud University Medical Center in the Netherlands recently found that the 1972 reform brought about no observable changes in long-term .
Unearthing whether, or how, education protects against dementia is critical to better understanding the condition. Natural experiments may be our best tool to do so 鈥� and another of them could be on the horizon.
The covid-19 pandemic shut school gates around the world, forcing students into at-home learning. If this translates into lower cognitive function, dementia cases could uptick in the decades to come, says Fjell.
