The health benefits of physical activity are undeniable.
However, a recent study based on data published over the last 30 years calls the famous saying into question Mens sana in corpore sano (a healthy mind in a healthy body) and questions the importance of exercise for both brain health and cognition.
A few days after that study was published, our team of health and neuroscience researchers released the results of our study of more than a quarter of a million people. Our results clearly support the beneficial effects of both moderate and vigorous physical activity on cognitive functioning, stimulating an important scientific debate.
Who is right and who is wrong? Here’s what science says.
Is physical exercise useless for cognitive functioning?
Tea the first study it was published on March 27, 2023. It is a review of 24 meta-analyses examining data from 11,266 healthy people using a more rigorous approach.
almost Although all of the 24 meta-analyses included in this review concluded that exercise has a positive effect on cognitive function, the authors argue that the analyzes conducted were suboptimal. For example, they point out that baseline levels of physical activity and the tendency of the scientific community to publish only significant results have rarely been taken into account. After these adjustments were made, the authors found results suggesting that the benefits of exercise are actually smaller than those estimated in previous meta-analyses, and may even be negligible.
Based on these findings, the authors argue that public health agencies such as the World Health Organization (WHO) should no longer state that physical activity improves cognitive health, academic performance, and executive function“at least until more reliable scientific evidence accumulates.”
Well, it didn’t take long for that evidence to arrive.
Genetics and DNA to the rescue
Tea another studyours, a genetic study involving nearly 350,000 people, was published four days later on March 31, 2023. Our results provide scientific evidence for the cognitive benefits of moderate to vigorous physical activity.
This evidence is based on the two-sample Mendelian randomization method, which exploits random variations in our DNA that occur at conception, before we are even born.
When any two people are compared, 99.9 percent of their genetic material is identical. DNA can be thought of as a long chain of building blocks, called nucleotides, that differ every 1,000 blocks between these two humans. There are four types of random dice: thymine, adenine, guanine, and cytosine. Genetic variation can result, for example, in a brick of cytosine at one site in one person’s DNA and a brick of thymine at the same site in another.
The first sample in our study, consisting of 91,084 people, was used to identify genetic variations associated with differences in physical activity, measured motion sensors worn on the wrist.
Another sample in our study, consisting of 257,854 people, was used to test whether genetic variation associated with physical activity has a proportional effect on cognitive functioning. Since this was the case, we could conclude that there is a causal effect of physical activity on cognitive function.
Moderate exercise helps
In our research, we show that physical activity improves cognitive functioning, but more importantly, that the effect of moderate physical activity (brisk walking, cycling) is 1.5 times greater than the effect of intense physical activity (running, playing basketball). This finding highlights that we don’t have to push ourselves to the point of exhaustion to reap the cognitive benefits of exercise.
When all types of physical activity were considered together (including sitting and light physical activity), our results no longer showed an effect on cognitive function. This finding confirms the importance of achieving at least moderate intensities in order to reap the cognitive benefits of physical activity.
Our results are consistent with those of a a recent study which emphasizes the importance of exercise duration and intensity for the release of a protein called BDNF in the brain. This protein is involved in the creation of new neurons, new connections between these neurons and new blood vessels that feed them.
This protein, whose production increases during exercise, is therefore one of the physiological mechanisms that explains the beneficial effects of physical activity on cognitive function. The mere existence of this explanatory mechanism additionally enhances the results by supporting the beneficial effect of exercise on the brain.
It’s never too late to start
Several differences may explain the discrepancy in results between the review of meta-analyses and our genetics-based study.
First, the review looks only at healthy people, which is not the case in our study. Second, our study differentiates between light, moderate and vigorous physical activity, whereas the review does not make this distinction. Finally, our genetic approach assesses long-term effects, over a lifetime, while the review is based on interventions lasting between one month and two years.
Since we’re dealing with the time aspects of physical activity here, it’s important to remember that it’s never too late to start exercising. In fact, in 2019 study showed that late onset of activity has the same overall positive health effects as activity throughout life.
Conclusion: Hasty decisions are never good
Based on our findings, it appears that physical activity can still be considered beneficial for brain health and cognition. Moreover, in the current socio-political climate of mistrust of science, we should not jump to conclusions based on one study that contradicts years of research based on the same data.
As is often the case in science, it is wiser not to make hasty decisions but to wait for more research before proposing changes in physical activity guidelines. Gathering converging evidence from different research teams should be a prerequisite for changing public health messages. As this article shows, we are nowhere near that point, and the benefits of physical activity on a wide range of physical and mental health outcomes remain undeniable.