What’s good for your heart is good for your brain. Just as physical activity helps keep our bodies fit and strong as we age, it also helps maintain our cognitive function – and is even linked with lower dementia risk.
Yet beyond the longer term cognitive benefits of physical activity, exercise also seems to give a short-term boost to cognitive performance lasting from minutes to hours. According to our latest study, this cognitive boost may last up to 24-hours after exercising. Because some cognitive abilities start to decline as we get older, even small boosts to cognitive function can help keep us active and independent for longer.
Studies conducted both in the lab and real-world settings have shown that people who are more physically active – whether that’s in the form of structured workouts or they just do more activity in their day-to-day lives – perform better on cognitive tests in the hours after exercising.
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 that 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 wore 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 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.
Mikaela Bloomberg is Senior Research Fellow, Department of Epidemiology and Public Health, UCL.
This article was first published on The Conversation.
