Each additional year of education is associated with around an 11% reduction in the risk of Alzheimer’s disease, a new study found. The work examined the genetic make-up and modifiable risks of around 17,000 people with Alzheimer’s, the most common form of dementia.
Researchers assessed 24 risk factors for dementia and found that education showed the strongest association with the risk of Alzheimer’s disease. But rather than checking all 17,000 people’s educational history, the researchers looked for genetic variants that have been linked to spending longer in education.
The study was carried out by researchers from the Karolinska Institutet, the University of Cambridge, the Ludwig-Maximilian University and German Centre for Neurodegenerative Diseases.
The study looked at a case-control population made up of 2 groups: people who had Alzheimer’s disease and a comparison group of people who did not. It’s aim was to estimate which potentially modifiable risk factors – including socioeconomic status, lifestyle and diet – are associated with Alzheimer’s disease. This was done by looking at genetic variants associated with those risk factors.
This study didn’t involve looking at specific genes “for” particular conditions. Rather, it looked at much smaller genetic variants found to be associated with particular traits. This is how the researchers were able to look at variants “associated with” spending longer in education.
The assumption is that if education wasn’t linked to dementia, the spread of these variations would be equal among the people who had Alzheimer’s disease and those who didn’t.
Researchers identified 24 modifiable risk factors they thought might be associated with Alzheimer’s disease. They included time spent in education, smoking, obesity, and a range of other factors related to lifestyle.
They then looked at previous studies to identify small genetic variations associated with those risk factors but not linked to each other, and tested whether these risk factors correlated with the development of dementia.
The study found that having genetic variations predicting that a person would have more years of education was associated with a lower risk of Alzheimer’s disease. Each predicted additional year of education was associated with a further lowering of the risk (odds ratio [OR] 0.89; 95% confidence interval [CI] 0.84 to 0.93).
Genetic variations predicting whether people had completed college or university were also associated with a lower risk of Alzheimer’s (OR 0.73; 95% CI 0.57 to 0.93). There was a possible relationship between genetic variants that predicted intelligence and developing Alzheimer’s disease.
None of the other risk factors as predicted by genetic variants were associated with developing Alzheimer’s.
The researchers pointed out that their method had the benefit of being free from some of the biases that can affect more direct approaches to studying risk factors for complex disease pathways like Alzheimer’s.
However, they noted the different populations that made up the overall study population had used different definitions of Alzheimer’s disease, which may have led to some people being put into the wrong group.
This study appears to support previous findings that spending more time in education may be beneficial to long-term health, but it had a number of limitations-
the people in the study were classified at a single point in time as either having Alzheimer’s disease or not
we don’t know anything about how old they were when this happened or how severe their condition was
it’s not clear whether anyone in the control group might have subsequently developed dementia
as the researchers themselves pointed out, the lack of a consistent definition of Alzheimer’s disease throughout the study population may have caused some people to be classified incorrectly, affecting the accuracy of the results
All things considered, it’s unclear what can be concluded from this one particular study. But when taken alongside other research, it does add weight to the idea that keeping your mind active may be helpful as you grow older.
Larsson Susanna C, Traylor Matthew, Malik Rainer, Dichgans Martin, Burgess Stephen, Markus Hugh S et al. Modifiable pathways in Alzheimer’s disease: Mendelian randomisation analysis BMJ 2017; 359 :j5375
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