By Ankur Banerjee

A recent study suggests that light physical activity may help stave off signs of aging in the brain.

The human brain typically shrinks as people age, with volume declining by about 0.2 percent per year by age 60 and with excessive shrinkage linked with cognitive problems, Nicole Spartano of Boston University School of Medicine and colleagues explain in JAMA Network Open.

Their new research, done in middle aged adults, found that each additional hour spent in light physical activity was associated with 0.22 percent higher brain volume. And spending 10 to 19 minutes per day in moderate-intensity physical activity, like brisk walking, was linked with 0.29 percent higher brain volume, compared to averaging less than 10 minutes per day.

Those activity levels are lower than what guidelines suggest is necessary to achieve substantial health benefits. Guidelines typically say adults should aim for at least 150 minutes per week of moderate-intensity physical activity (about 21 minutes per day), or 75 minutes per week of vigorous exercise, and at least 10,000 steps per day.

In the new study, individuals who took at least 7,500 steps per day had larger brain volumes than those averaging fewer than 7,500 steps per day.

The researchers estimate that each additional hour of light-intensity physical activity was associated with approximately 1.1 years less brain aging – although they caution that because participants were relatively young, this estimate might not be accurate.

They also note that the link between activity levels, step counts and brain volume was not consistent, with a smaller benefit seen at the highest levels of exertion.

For the study, the researchers had 2,354 middle-aged volunteers wear a small accelerometer for at least three days (and up to eight days), to measure their energy expenditure and step counts. The researchers also used magnetic resonance imaging to assess participants’ brain volume in relation to their skull volume.

“There shouldn’t be very much extra space in the skull that is not filled by brain tissue. If we see lots of extra space than this suggests that the brain may have atrophied or shrunk and is linked to dementia,” Spartano told Reuters Health by email.

The finding that the lowest levels of physical activity were linked with smaller brain volume even in middle age suggests that “some adults may enter older age with lower brain volumes, putting them at a disadvantage for maintaining this already depleted tissue,” she and her colleagues write in their report.

Yaakov Stern, a professor of neuropsychology at the Columbia University Medical Center in New York City who was not involved in the research, pointed out to Reuters Health that the study only looked at brain volume and not whether different amounts of physical activity translate into real-life benefits in cognitive function or reduced risk of dementia.

Furthermore, observational studies like this one can’t prove cause and effect.

“Follow up trials where people are randomized to specific conditions consisting of different intensities of exercise can help explore more definitively what degree of physical activity is required for increased brain health,” Stern said in an email.

SOURCE: JAMA Network Open, online April 19, 2019.