Moving is good for the body… and for the brain. A large-scale American study shows that regular physical activity, even when started after age 45, can significantly reduce the risk of dementia, including in people with a genetic predisposition. This is further proof that exercise remains one of the best ways to keep your mind sharp as you age.

For years, scientists have known that moving our bodies can sharpen our minds. Indeed, physical activity stimulates blood flow to the brain , improves neuroplasticity , and reduces chronic inflammation . These processes are considered protective against cognitive decline , including the risk of dementia .

Yet, despite decades of research, important questions remain. Does physical activity reduce the risk of dementia when practiced at any age? Or only when one is young? And if one has a higher genetic risk, can physical exercise still make a difference?

A new study, just published in the medical journal JAMA Network Open, provides some of the clearest answers available to date. Based on data from the long-term Framingham Heart Study epidemiological study conducted in the United States, its findings confirm what many clinicians were already telling their patients: exercise is beneficial.

What did this study consist of?

This new research is based on data from 4,290 members of the Framingham Heart Study Offspring cohort. Begun in 1948 , this study aimed to investigate long-term cardiovascular risk factors. At its inception, researchers recruited more than 5,000 adults over the age of 30 residing in Framingham, Massachusetts, USA.

In 1971, a second generation of participants (more than 5,000 children from the initial cohort—now adults—and their spouses) was recruited to form the “Offspring” cohort . The health of this generation was monitored through regular health checkups conducted every four to eight years.

As part of the work published in JAMA Network Open , participants self-reported their physical activity . This involved documenting both basic daily activities, such as climbing stairs, and more intense physical exercises.

The volunteers first completed the questionnaire in 1971, and the process was repeated for several decades thereafter. Depending on their age at the time of their initial assessment, participants were divided into three categories  :

• young adults (26-44 years old): assessed at the end of the 1970s;
• middle-aged people (45-64 years): assessed in the late 1980s and 1990s;
• elderly people (65 years and over): assessed in the late 1990s and early 2000s.

To assess the influence of physical activity on the risk of dementia, researchers observed, within each age group, the number of people who had developed dementia, and at what age the diagnosis was made.

They then compared the patterns of physical activity (low, moderate, high) in each of the age groups, in order to determine if a link could be established between the amount of exercise and the onset of dementia.

The study authors also identified individuals with the APOE ε4 allele, which is known to be a genetic risk factor for Alzheimer’s disease .

What have the scientists discovered?

During the follow-up period, 13.2% (567) of the 4290 participants developed dementia. The individuals affected were primarily in the oldest group of volunteers.

This rate is relatively high compared to other longitudinal (i.e., long-term) studies on dementia or the levels of dementia risk recorded in Australia (8.3% of Australians over 65 currently have dementia, or about 1 in 12).

By analyzing the data, the researchers discovered a striking trend: people who reported the highest levels of activity in middle age and old age had a 41 to 45 percent lower risk of developing dementia than those who reported the lowest levels.

This association persisted even after taking into account other risk factors, whether demographic (age, education) or medical (hypertension, diabetes).

It is interesting to note that being physically active in early adulthood had no influence on the risk of dementia.

The analysis of the influence of the APOE ε4 genetic factor , a known risk factor for Alzheimer’s disease, constitutes one of the major advances of this study. It has highlighted the following points:

• In middle age, engaging in more intense physical activity only reduced the risk of developing dementia in people who did not carry the allele;
• In contrast, at an advanced age, having more intense physical activity reduced the risk in both carriers of the allele and those who did not possess it.

In other words, for people genetically predisposed to dementia, remaining active at an advanced age could continue to offer significant protection.

What is the significance of these results?

These findings reinforce what scientists already know: physical exercise is good for the brain.

This study is distinguished not only by the large size of its sample, but also by the exceptional duration of its follow-up and by the fact that it conducted a genetic analysis covering different periods of the participants’ lives.

The fact that it has been revealed that engaging in physical activity in middle age can have a different effect depending on genetic risk, while staying active at an advanced age benefits almost everyone, could be used to enrich public health messages .

A study that has some limitations

In this study, the estimated level of physical activity relies largely on self-reporting. Therefore, there is a risk of recall bias ( participants tend to remember the event – ​​in this case, their physical activity – differently from how it actually was ). Furthermore, it is unknown which types of exercise are most beneficial.

Because the number of dementia cases among the youngest participants was low, the scope of the conclusions is more limited with regard to early adulthood.

The chosen cohort, consisting of participants who are mostly descended from European populations and all come from the same city, limits the generalization of the results to more diverse populations.

This is particularly important, given that there are significant inequalities worldwide in the risk of dementia and in the diagnosis of this condition .

What conclusion can be drawn from this study?

Currently, knowledge about dementia and its risk factors remains limited in ethnically diverse groups . In many places, it is still often perceived as a “normal part” of aging.

The conclusion to be drawn from this study, however, can be summed up in two sentences: move more, whatever your age . The benefits you will reap clearly outweigh the risks.