New study shows exercise can boost memory for up to 24 hours, especially in older adults

But one question researchers are still trying to answer is how long these cognitive benefits last – particularly in older adults, where maintaining cognitive function is very important. This is what our research aimed to do.

In our study of middle-aged and older adults, we found that people who did more moderate to vigorous physical activity (such as jogging or cycling) performed better on memory tests the following day. This suggests the memory benefits of physical activity might last longer than the couple of hours found in previous, lab-based studies.

Our study involved 76 participants aged 50-83. Each participant donned a wrist-worn activity tracker for eight days and nights. They were instructed to go about their daily lives as usual. From these activity trackers, we were able to see how much time participants spent being sedentary or physically active each day – and how intense this physical activity was.

Because physical activity also affects sleep quality – particularly the amount of time spent in the deepest and most restorative sleep phase, referred to as slow-wave sleep – we were also interested in exploring the role of sleep in cognitive performance. We extracted sleep quality characteristics from the activity trackers, including total sleep duration and time spent in slow-wave sleep.

On each day the participants wore the activity trackers, they also took a set of cognitive tests. Some of these cognitive tests assessed episodic memory (being able to recollect previous experiences) and working memory (the ability to temporarily store information in the mind). The type of cognitive tests the participants were given alternated each day to reduce the chances of participants learning and remembering the answers.

We wanted to be sure we had isolated the effect of physical activity and sleep on next-day cognitive performance. So, we took into account a number of demographic, socioeconomic and lifestyle characteristics that could have distorted the results. Each day, we also accounted for a participant’s previous cognitive score to be sure we were focusing on day-to-day improvements in cognitive performance.

Memory boost

We found that the more time a participant spent doing moderate to vigorous physical activity, the better their episodic and working memory scores were the following day. Getting more sleep, particularly slow-wave sleep, was also associated with improvement in memory scores – independently of physical activity. But people who were more sedentary had worse working memory scores the following day.

While the improvement in memory performance was relatively modest, none of our participants had a cognitive impairment or dementia. So they realistically did not have much room to improve on these tests to begin with.

But these results could serve as a jumping-off point for future studies examining next-day cognitive performance in people with neurodegenerative diseases – such as dementia, where we might see larger improvements in test scores. These findings also need replicating in a larger study before we can be sure of them.

The short-term cognitive benefits of exercise are thought to occur because exercise stimulates blood flow and the release of specific brain chemicals that contribute to cognitive function. Generally, these neurochemical benefits are thought to last a couple hours following exercise. However, other changes induced by exercise – including some implicated in memory function – might last for 24-48 hours following exercise. This might underlie the results we found in our study.

Our findings point to the importance of maintaining active lifestyles as we age, and supporting this active lifestyle with good sleep.