Light Physical Activity Tied to Brain Volume

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Light Physical Activity Tied to Brain Volume

Potential benefits on brain aging may accrue at lower activity levels

• by Judy George, Senior Staff Writer, MedPage Today April 19, 2019

Incremental physical activity, even at a light intensity, was tied to larger brain volume, an analysis of middle-age adults in the Framingham Heart Study showed.
Each additional hour of light-intensity physical activity per day was associated with higher cerebral total brain volume, even among people not meeting national physical activity guidelines, reported Nicole Spartano, PhD, of the Boston University School of Medicine, and colleagues in JAMA Network Open.
"The research emphasizes the relationship we are seeing between people doing more light-intensity physical activity and also having maintained brain structures," Spartano said.
Past research has focused on moderate to vigorous physical activity, as have the U.S. Health and Human Services guidelines, she noted, but many adults are unable to meet the national exercise guidelines of 150 minutes of moderate to vigorous physical activity a week.
"Our study results don't discount moderate or vigorous physical activity as being important for healthy aging," Spartano told MedPage Today. "We are just adding to the science, suggesting that light-intensity physical activity might be important, too, especially for the brain."
The analysis compared the number of steps walked per day and dose of exercise (intensity x duration) with MRI total cerebral brain volume in 2,354 third-generation Framingham Heart Study participants who were a mean age of 53. The sample was predominantly white; 54.2% were women and 46.7% met the nationally recommended physical activity guidelines, averaging at least 21.4 minutes of moderate to vigorous physical activity per day. People with stroke, dementia, or other disorders that might affect brain MRI measures were excluded.
Each participant wore a hip-belt accelerometer for 8 days. The researchers classified activity measures of 200-1,486 counts/min as light activity and >1,486 counts/min as moderate to vigorous activity.
Their analysis showed:

• Each additional hour of light-intensity physical activity per day was associated with approximately 1.1 years of less brain aging (β estimate 0.22, SD 0.07; P=0.003).
• For people who didn't meet the physical activity guidelines, each hour of light-intensity activity (β estimate 0.28, SD 0.11; P=0.01) and achieving 7,500 steps or more per day (β estimate 0.44, SD 0.18; P=0.02) were associated with higher total brain volume, equal to about 1.4 to 2.2 years of less brain aging.
• Achieving 10,000 or more steps a day was associated with higher brain volume compared with fewer than 5,000 steps per day.

After adjusting for light-intensity activity, increasing moderate to vigorous activity levels was not significantly associated with total cerebral brain volume.
The overall results suggest the threshold of the favorable association for physical activity with brain aging may be at a lower, more achievable level of intensity and duration, the researchers noted.
"The main finding that physical activity, even fairly light, seems beneficial to brain volume maintenance is of considerable interest from a public heath viewpoint," said James Mortimer, PhD, of the University of South Florida School of Public Health, who was not involved with the study.
"Brain atrophy is a major correlate of dementing illnesses," Mortimer told MedPage Today. "Starting with more brain volume, therefore, may delay onset of these illnesses, including Alzheimer's."
But other variables may have affected the findings in this study, he observed. "We know from several published studies that greater education is associated with greater brain volume, especially gray matter," he said. "The effect reported here on physical activity and brain volume could in part be due to the association between more education and larger brain volumes."
The study had other limitations, the researchers noted. It was cross-sectional and time relationships between physical activity and brain volume were unknown. Brain atrophy also may have led to changes in physical activity.
Longitudinal studies with longer follow-up times are needed, they added. "It will be important to test whether light-intensity physical activity interventions in older adults can actually play a role in healthy brain aging," Spartano said. "We don't have effective preventions or treatment solutions to address the growing public health crisis of climbing dementia rates. So focusing on lifestyle interventions, which have shown some potential benefit, are vital at this point."
Because certain minority populations may have higher risks of developing dementia, effective prevention measures also need to be studied in different race, ethnic, and socio-economic groups, she added.

This study was funded by grants from the National Heart, Lung, and Blood Institute, the National Institutes of Health, the National Institute on Aging, the National Institute of Neurological Disorders and Strokes, and the American Heart Association. Researchers reported no conflicts of interest.

last updated 04.18.2019

• Primary Source

  JAMA Network Open

  Source Reference: Spartano N, et al "Association of Accelerometer-Measured Light-Intensity Physical Activity With Brain Volume: The Framingham Heart Study" JAMA Network Open 2019; doi:10.1001/jamanetworkopen.2019.2745.