Longevity Briefs: Does Physical Fitness Prevent Dementia In Those Most At Risk?

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

The problem:

As the global population ages, cognitive decline and neurodegenerative diseases like Alzheimer’s become growing concerns. Dementia remains incurable, but recent research suggests that around 45% of cases are caused by preventable risk factors. Many prominent risk factors such as high LDL cholesterol, type 2 diabetes and hypertension can be mitigated with physical exercise (along with a healthy diet of course). However, we also know that dementia risk has a large genetic component. Can people with a genetic predisposition to dementia still cut their risk by staying physically fit? Surprisingly, we don’t actually have that much data addressing this question. This study attempts to fix that, as well as taking a wider look at how cardiorespiratory fitness affects cognitive function and dementia risk.

The discovery:

Researchers looked at data from 61,214 participants of the UK biobank who were aged 39-70 years old and free of dementia when they enrolled in 2009-2010. Participants took cognitive tests and had their cardiorespiratory fitness assessed through a 6 minute exercise session, which allowed researchers to estimate maximum heart rate, work rate and oxygen consumption. The study then followed participants for up to 12 years.

They found that high cardiorespiratory fitness was associated with significantly better cognitive function at the start of the study, including improved memory and processing speed. Higher cardiorespiratory fitness was also associated with lower risk of developing dementia: compared to having low fitness, high fitness was associated with a 40% reduction in all dementia risk and delayed onset by 1.48 years on average. When looking at specific forms of dementia, this reduction was 38% for Alzheimer’s disease 23% for vascular dementia, though the latter did not reach statistical significance.

Lastly, researchers looked at dementia cases according to genetic risk scores for Alzheimer’s disease and found that among those with moderate to high genetic risk, high cardiorespiratory fitness was associated with a 35% reduction in dementia risk compared to low/moderate fitness. It is however worth noting that those with a low genetic risk score were still less likely to develop dementia regardless of their cardiorespiratory fitness.

The implications:

This study provides further evidence that higher cardiorespiratory fitness is associated with both higher cognitive performance and reduced risk of dementia. While the relationship between fitness and protection from vascular dementia was not statistically significant, this may have been because there were relatively few occurrences of vascular dementia during the study. The more novel finding here is that high cardiorespiratory fitness appears to still be very valuable among those with a genetic predisposition to dementia, though it doesn’t seem to fully counteract it. This suggests that improving cardiorespiratory fitness through regular physical activity should be a priority for dementia prevention even if you think or know you are at high risk. As for why this is the case, poor cardiorespiratory fitness is not only an indicator of overall health, but is also related to reduced blood supply to the brain, which is likely to accelerate neurodegeneration in multiple ways.

This study was an observational study – it didn’t randomly assign participants to an exercise routine and measure the outcomes, but only looked at whether people who were already fit at the start of the study got less dementia. This means we can’t be certain that cardiorespiratory fitness was entirely responsible for all of the benefits, as people with high cardiorespiratory fitness are likely to be healthier in other ways, though the researchers did attempt to control for confounding factors as well as possible. Another limitation was that cardiorespiratory fitness was only assessed at the beginning of the study. This means we don’t know if the fittest people stayed fit and vice versa, which could make the impact of fitness appear less than it actually is.