Education may help reduce the risk of Alzheimer's disease

Monday December 11 2017

"Alzheimer's risk 'falls by 11% for every year spent in education'," reports the Mail Online.

This was based on a study that looked at the genetic make-up and modifiable risks of around 17,000 people with Alzheimer's disease, the most common form of dementia.

The 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.

They estimated that each additional year of education was associated with around an 11% reduction in the risk of Alzheimer's disease.

But because of the way they measured educational attainment, as well as some other assumptions they made, it's hard to know how accurate this estimated reduction might be.

However, it's never too late to learn something new. There's a good body of evidence that all types of learning improve mental wellbeing, whether that's a new language or how to sail a boat.

Where did the story come from?

The study was carried out by researchers from the Karolinska Institutet in Sweden, the University of Cambridge in the UK, and the Ludwig-Maximilian University and German Centre for Neurodegenerative Diseases, both in Germany. It was funded by the European Union's Horizon 2020 research and innovation programme, and the Swedish Brain Foundation.

The study was published in the peer-reviewed British Medical Journal.

The Mail Online did a good job of explaining what the researchers did, especially given how complex the methodology was.

However, it reported the hypothesis that the relationship between education and Alzheimer's risk could be explained by the concept of "cognitive reserve" – for example, that it may be a case of "use it or lose it" when it comes to the brain – but this was a speculation on the part of the researchers and wasn't directly tested in this research.

What kind of research was this?

This 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.

The aim of this research 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.

What did the research involve?

This study looked at 17,008 people with Alzheimer's disease and a control group of 37,154 people without the disease. All were of European ancestry and recruited from the International Genomics of Alzheimer's Project. This is an ongoing international project that analyses DNA from volunteers.

The researchers identified 24 modifiable risk factors they thought might be associated with Alzheimer's disease. These 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 researchers defined at the outset what threshold they would use to determine whether a risk factor was statistically significant (a clear relationship), "suggestively associated" (a possible relationship) or not significant (no relationship).

It's important to do this, particularly in studies where lots of different risk factors are being considered.

What were the basic results?

The study found the following:

  • 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.

How did the researchers interpret the results?

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.

Conclusion

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 we can conclude from this 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.

Analysis by Bazian
Edited by NHS Website