Exercise in leisure time best to ward off Alzheimer's

A new systematic review, published in The Lancet Public Health, has examined how different types of physical activity are associated with the risk of all-cause dementia, Alzheimer’s disease and vascular dementia.

The meta-analysis combined data from 74 studies including more than four million adults across 30 countries. However, nearly half the studies were rated low quality, findings varied considerably, and the certainty of some evidence was minimal.

Overall, higher levels of physical activity were associated with a lower risk of dementia, with the clearest association seen for leisure-time physical activity. People who were the most physically active in their leisure time had a 24% lower relative risk of dementia compared with those who were least active, although the review cannot prove that exercise itself caused this difference.

In contrast, work and commuting-related physical activity was associated with higher relative dementia risk, but these findings were based on just five and two studies, respectively.

As this review was based on observational studies, it cannot prove cause and effect. It suggests the context of physical activity may matter, but further research is needed to separate the effects of activity itself from wider factors linked to leisure, work and commuting.

Dr Susan Kohlhaas, Executive Director of Research and Partnerships, at Alzheimer’s Research UK:
“People should not conclude from this study that having a physically demanding job, or walking or cycling to work, increases the risk of developing dementia. We already know that regular physical activity supports brain health. This study asks a more specific question about whether activity in different contexts is associated differently with dementia risk.

“Our advice remains that what is good for your heart is good for your brain.”

“An analysis involving more than four million people sounds definitive, but size cannot make up for weaknesses in the underlying evidence. Nearly half of the 74 studies were rated low quality and findings varied considerably across studies. This makes it difficult to draw firm conclusions. The most consistent finding, that leisure-time physical activity was associated with a lower risk of dementia, supports what we already know about the importance of physical activity for brain health.

“The analysis cannot establish cause and effect. The findings relating to physical activity at work and while commuting may instead reflect factors such as working conditions, socioeconomic circumstances, stress or exposure to pollution.

“Our advice remains that what is good for your heart is good for your brain. Regular physical activity is an important part of looking after your brain health, alongside staying mentally and socially active. Through our Think Brain Health initiative, people can find realistic and sustainable ways to build these habits into everyday life.

“This analysis also highlights the need to keep strengthening the evidence for dementia prevention. To give people advice they can act on with confidence, we need long-term studies that measure activity accurately over time, account for the different circumstances in people’s lives, and test whether changing behaviour genuinely changes dementia risk.”