What is good for the heart is good for the brain: physical activity not only keeps our body in shape and maintaining our physical strength as we age, but it also helps to preserve our cognitive functions. It was notably associated with a decrease in the risk of dementia.
It would also seem that the cognitive benefits of the exercise are not only felt in the long term. Indeed, physical activity also seems to offer a short -term boost to our brain. According to our latest study, the resulting cognitive gain could last up to twenty-four hours. Since certain cognitive capacities decline with age, any improvement is good to take, in order to remain active and independent as long as possible …
A “boost” which lasts from a few minutes to several hours
Various research works, carried out in the laboratory or in real conditions, had revealed that people physically active – when they train regularly or simply because they move more than others in their daily lives – obtain better results from cognitive tests in the hours following the exercise than less active individuals.
However, a question remained: how long do these cognitive benefits last, especially in the elderly, for whom the maintenance of cognitive functions is essential?
To answer this question, we have analyzed the cognitive performance of sixty-six British adults aged 50 to 83. Each participant was equipped with an activity tracker on the wrist for eight days and eight nights, which he carried by continuing his usual activities. Thanks to these devices, we were able to determine the daily duration spent in activity or by being sedentary, as well as the intensity of physical activity.
We also tried to explore the role of sleep in cognitive performance. Indeed, we know today that physical activity also affects the quality of sleep – notably the time spent in the deep and restful sleep phase, called sleep with slow waves. For this, we have extracted the statements provided by activity trackers a certain number of data related to the quality of sleep, such as the total duration of sleep and the time spent in slow sleeping phase.
Participants equipped with trackers have also passed a series of daily cognitive tests intended in particular to assess episodic memory (the ability to remember past experiences) and working memory (the ability to temporarily store information in the mind). The type of administered cognitive tests changed every day, in order to reduce the learning and habitation effects to responses.
In addition, in order to ensure that the cognitive performance of the next day was well linked to the effects of physical activity and sleep, we have taken into account various demographic, socio-economic characteristics and linked to the lifestyle that could have distorted the results. Finally, we have checked, for each participant, the cognitive score of the day before, in order to assess cognitive improvements from one day to the next.
A slight improvement in memory
Our results indicate that people practicing more physical activity of moderate intensity in vigorous (such as jogging or bicycle) obtained better scores than others with episodic memory and working memory tests carried out the next day. Previous studies, carried out in the laboratory, had already suggested that the benefits of the exercise on memory could last a few hours. Our own work tends to suggest that this effect could actually be longer.
Better sleep quality – in particular during the slow wave sleep phase – has also proven to be associated with an improvement in memory scores, regardless of physical activity. We also found that the more sedentary people than the others obtained less good scores in working memory the following day.
It should be noted that the improvement in the performance observed is relatively modest, none of the participants suffering from cognitive disorders.
The short -term cognitive benefits obtained as a result of the practice of physical activity could result from the increase in blood flow and the release of specific chemicals by the brain resulting from the exercise. We know that some of these substances contribute to cognitive function, and that in general, their neurochemical effects are supposed to last a few hours.
Other changes induced by exercise-some involved in the memory function-could persist for twenty-four to forty-eight hours after physical activity, which could explain the results observed in our study.
It should be noted that the improvement in the performance observed is relatively modest; None of the participants in our study suffering from cognitive disorders, the margin for improving their capacities was probably not very important. Future studies will have to be carried out to assess whether people with neurodegenerative diseases – such as dementia, for example – have more significant improvements.
Our results must also be confirmed by work carried out on a larger cohort. In the meantime, they suggest that it is important, as one ages, not only to remain active, but also to sleep properly.
