One type of physical activity protects the brain more than others, study find

People jog through the Central Experimental Farm during heavy fog and rain in Ottawa, on Saturday, Dec. 31, 2022. (THE CANADIAN PRESS/Spencer Colby)

What if you could look at all the things you do daily — walking from room to room, preparing a presentation at your desk, running up and down stairs to deliver folded laundry or taking a jog around the block — and know which ones will best help or hurt your brain?

A new study attempted to answer that question by strapping activity monitors to the thighs of nearly 4,500 people in the United Kingdom and tracking their 24-hour movements for seven days. Researchers then examined how participants' behavior affected their short-term memory, problem-solving and processing skills.

Here's the good news: People who spent "even small amounts of time in more vigorous activities — as little as six to nine minutes — compared to sitting, sleeping or gentle activities had higher cognition scores," said study author John Mitchell, a Medical Research Council doctoral training student at the Institute of Sport, Exercise and Health at University College London, in an email.

Moderate physical activity is typically defined as brisk walking or bicycling or running up and down stairs. Vigorous movement, such as aerobic dancing, jogging, running, swimming and biking up a hill, will boost your heart rate and breathing.

The study, published Monday in the Journal of Epidemiology & Community Health, found doing just under 10 minutes of moderate to vigorous exertion each day improved study participants' working memory but had its biggest impact on executive processes such as planning and organization.

The cognitive improvement was modest, but as additional time was spent doing the more energetic workout the benefits grew, Mitchell said.

"Given we don't monitor participants' cognition over many years, this may be simply that those individuals who move more tend to have higher cognition on average," he said. "However, yes, it could also imply that even minimal changes to our daily lives can have downstream consequences for our cognition."

Steven Malin, an associate professor in the department of kinesiology and health at Rutgers University in New Jersey, told CNN the study provides new insight in how activity interacts with sedentary behavior as well as sleep.

"Understanding the interaction of sleep and various physical activities is often not examined," said Malin, who was not involved in the new study.

While the study had some limitations, including a lack of knowledge about the health of the participants, the findings illustrate how "the accumulation of movement patterns in a day to a week to a month is just as, if not more important, than just getting outside for a single session of exercise," he said.

A decline in cognition

There was bad news as well: Spending more time sleeping, sitting or engaged only in mild movement was linked to a negative impact on the brain. The study found cognition declined one to two per cent after replacing an equivalent portion of moderate to vigorous physical activity with eight minutes of sedentary behavior, six minutes of light intensity or seven minutes of sleep.

"In most cases we showed that as little as seven to ten minutes less MVPA (moderate to vigorous physical activity) was detrimental," Mitchell said.

That change is only an association, not a cause and effect, due to the observational methods of the study, Mitchell stressed.

In addition, the study's findings on sleep can't be taken at face value, he said. Good quality sleep is critical for the brain to operate at peak performance.

"The evidence on the importance of sleep for cognitive performance is strong," Mitchell said, "yet there are two major caveats. First, over-sleeping can be linked to poorer cognitive performance.

"Secondly, sleep quality may be even more important than duration. Our accelerometer devices can estimate how long people slept for, but cannot tell us how well they slept."

Additional studies need to be done to verify these findings and understand the role of each type of activity. However, Mitchell said, the study "highlights how even very modest differences in people's daily movement — less than 10 minutes — is linked to quite real changes in our cognitive health."