Study finds those with the highest levels of activity were 41-45 per cent less likely to develop dementia than those wihh lowest levels of activity

By Joyce Siette

For years, scientists have known that moving our bodies can sharpen our minds. Physical activity boosts blood flow to the brain, enhances neuroplasticity and reduces chronic inflammation. These processes are believed to protect against cognitive decline, including dementia.

Yet despite decades of research, major questions have remained unresolved.

Does exercising at any age help reduce your risk of dementia? Or only when you’re young? And what if you have a higher genetic risk – can exercising still make a difference?

New research from the long-running Framingham Heart Study in the United States offers some of the clearest answers to date. Their findings support what many clinicians already tell patients: exercise helps.

But the study also offers new insight into the potentially protective effect of staying active at the age of 45 and over – even for those with a certain genetic predisposition to dementia.

The new research draws on data from 4,290 participants enrolled in the Framingham Heart Study Offspring cohort. This study began in 1948, when researchers recruited more than 5,000 adults aged 30 and over from the town of Framingham, Massachusetts, to investigate long-term risk factors for cardiovascular disease.

In 1971, a second generation (more than 5,000 adult children of the original cohort, and their spouses) were enrolled, forming the Offspring cohort. This generation then had regular health and medical assessments every four to eight years.

In the new study, participants self-reported their physical activity. This included incidental activity such as climbing stairs as well as vigorous exercise.

Participants first reported these activities in 1971, and then again over several decades. Based on the age at which each participant was first evaluated, they were grouped into three categories:

young adulthood (26-44 years): assessed in the late 1970s

midlife (45-64 years): assessed during the late 1980s and 1990s

older adulthood (65 years and over): assessed in the late 1990s and early 2000s.

To examine how physical activity influences dementia risk, the researchers looked at how many people developed dementia in each age group and at what age they were diagnosed.

Then they considered physical activity patterns within age groups (low, moderate, high) to see if there was any link between how much exercise people did and whether they developed dementia.

They also looked at who had a known genetic risk factor for Alzheimer’s disease, the APOE ε4 allele.

Over the follow-up period, 13.2 per cent (567) of the 4,290 participants developed dementia, mostly in the older age group.

This is quite high compared with other long-term longitudinal dementia studies.

When researchers examined physical activity levels, the pattern was striking. Those with the highest levels of activity in midlife and later life were 41-45 per cent less likely to develop dementia than those who had the lowest levels of activity.

This was the case even after adjusting for demographic factors that increase dementia risk (such as age and education) and other chronic health factors (such as high blood pressure and diabetes).

Interestingly, being physically active during early adulthood did not influence dementia risk.

A key innovation of this study was its examination of the genetic risk factor, the APOE ε4 allele. This analysis suggests something new: in midlife, higher physical activity lowered dementia risk only in people who didn’t carry this genetic predisposition but in later life, higher physical activity lowered dementia risk in both carriers and non-carriers.

This means for people genetically predisposed to dementia, staying active later in life may still offer meaningful protection.

The findings largely reinforce what scientists already know: exercise is good for the brain.

The suggestion that midlife activity benefits some individuals differently depending on their genetic risk, while late-life activity benefits nearly everyone, may also add a new layer to public health messaging.

The takeaway is refreshingly simple though: move more, at any age. At this stage we know there are more benefits than harm.

Joyce Siette is Associate Professor | Deputy Director, The MARCS Institute for Brain, Behaviour and Development, Western Sydney University. This article is republished from The Conversation under a Creative Commons licence