Brain or muscles, which do we lose first?

Photo by Gerd Altmann

From the age of 50, there is a gradual decline not just in physical activity but also in cognitive abilities. The two are correlated, but which of them influences the other? An extensive longitudinal study has some surprising answers.

Does physical activity impact on the brain or is it the other way around? The literature in this area has been looking at the impact of physical activity on cognitive skills for a number of years.

Is it the chicken, or is it the egg?

“Correlations have been established between these two factors, particularly in terms of memory, but also regarding the growth and survival of new neurons,” begins Boris Cheval, a researcher at University of Geneva Swiss Centre for Affective Sciences.

“But we have never yet formally tested which comes first: does physical activity prevent a decline in cognitive skills or vice versa? That’s what we wanted to verify.”

How is our brain involved when it comes to physical activity?

Earlier studies based on the correlation between physical activity and cognitive skills postulated that the former prevents the decline of the latter.

Someone dies somewhere in the world every 10 seconds owing to physical inactivity. That’s 3.2 million people a year.

– World Health Organisation

“But what if this research only told half the story? That’s what recent studies suggest since they demonstrate that our brain is involved when it comes to engaging in physical activity,” continues the Geneva-based researcher.

More than 100,000 participants across Europe, 12 years of testing

The University of Geneva researchers tested the two possible options formally using data from the SHARE survey (Survey of Health, Aging and Retirement in Europe), a European-wide socio-economic database covering over 25 countries.

“The cognitive abilities and level of physical activity of 105,206 adults aged 50 to 90 were tested every two years over a 12-year period,” explains Matthieu Boisgontier, a researcher at the Lives Swiss National Centre of Competence in Research.

Cognitive abilities were measured using a verbal fluency test (naming as many animals as possible in 60 seconds) and a memory test (memorising 10 words and reciting them afterwards). Physical activity was measured on a scale of 1 (“Never”) to 4 (“More than once a week”).

Surprising results uncovered

The Geneva researchers employed this data in three separate statistical models.

In the first, they looked at whether physical activity predicted the change in cognitive skills over time; in the second, whether cognitive skills predicted the change in physical activity; and in the third, they tested the two possibilities bidirectionally.

“Thanks to a statistical index, we found that the second model adjusted the most precisely to the data of the participants,” says Cheval.

In other words, the findings show that — contrary to what was previously thought — cognitive abilities ward off inactivity much more than physical activity prevents the decline in cognitive abilities.

The best way to slow down the inevitable decline: exercise your brain

All this means that we need to prioritise exercising our brains.

“Obviously, it’s a virtuous cycle, since physical activity also influences our cognitive capacities. But, in light of these new findings, it does so to a lesser extent,” points out Boisgontier.

From the age of 50, the decline in physical and cognitive abilities is inevitable. However, these results indicate that, contrary to what was once thought, if we act first on our cognitive skills, we can slow the decline of this virtuous circle.

“This study backs up our theory that the brain has to make a real effort to get out of a sedentary lifestyle and that by working on cognitive capacities, physical activity will follow”, says Cheval by way of conclusion.

This article is based on materials provided by University of Geneva, Switzerland. Content may have been edited for style and length. If you want to find out more, please contact the cited source.

Original journal article: Cheval, B., Orsholits, D., Sieber, S., Courvoisier, D., Cullati, S., & Boisgontier, M. P. (2020). Relationship between decline in cognitive resources and physical activity. Health Psychology.