Even for people in their early ‘20s, exercise has lasting effects on the brain that may help protect against cognitive decline — the slow loss of certain brain functions that sometimes accompany aging. Now, even more research points to how exercise seems to help keep the brain younger for longer. Perhaps more importantly, even small amounts of exercise can make a difference if fighting against dementia is the goal.
A paper published Friday in JAMA Network Open uses fitness tracker data combined with fMRI brain scans to show how light exercise can reduce biomarkers of aging in the brain. This analysis, led by Nicole Spartano, Ph.D., an assistant research professor at Boston University’s School of Medicine, shows that every hour of light physical activity was associated with brain volume measurements equivalent to 1.1 fewer years of brain aging. When she and her team broke down the results even further, they found that hitting basic step-count thresholds seemed to also have powerful associations with keeping the brain young.
“There shouldn’t be very much extra space in the skull that is not filled by brain tissue,” Spartano tells Inverse.. “If we see lots of extra space, then this suggests that the brain may have atrophied or shrunk. This brain atrophy is a sign of neurodegeneration, linked to dementia.”
"We are just adding to the science, suggesting that light-intensity physical activity might be important too, especially for the brain!"
Her evidence comes from 2,354 individuals enrolled as part of the long-running Framingham Heart Study. Those individuals consented to having fMRI images taken of their brains and wore accelerometers (basic fitness trackers) that helped them keep track of their steps. Those steps, Spartano says, are measurements of light physical activity. Focusing on the health effects of these easy bouts of exercise, she explains, is a new trend in a field that has largely focused on the health benefits of moderate to vigorous exercise.
“Past research focuses more on moderate to vigorous physical activity, which is also the focus of guidelines from expert groups like the American Heart Association, American College of Sports Medicine, or the guidelines released by the US Health and Human Services agency,” she says. “We are just adding to the science, suggesting that light-intensity physical activity might be important too, especially for the brain!”
Step counts had powerful associations with lower rates of brain aging, not just for people who hit the government’s recommended 150 minutes of moderate to vigorous exercise per week, but also for people who fell short of that mark. People who averaged 10,000 steps or more per day tended to have .35 percent higher brain volume than those who averaged less than 5,000 steps per day. That additional activity, Spartano adds in the paper, was associated with the equivalent of 1.75 fewer years of brain aging.
Interestingly, she also found that people who struggle to reach the government’s weekly 150 minute guidelines can still benefit from getting a little bit of easy activity in during the day. In a separate analysis of participants who didn’t reach 150 minute per week goals, people who who still achieved 7,500 steps per day tended to have 2.2 fewer years worth of brain volume decline compared to those who didn’t hit that step count.
Taken together, Spartano says that her step count data shows that striving for getting just a few more steps in during the day can really make a difference when it comes to aging in the brain. But that’s not to say that it’s not worth striving to hit that 150 minute per week goal for other reasons. For example, she notes that people who exercised at least that much had lower levels of diabetes and cardiovascular disease.
But for those who feel like that amount is insurmountable, her results show the importance of creating smaller, more achievable thresholds that feel less daunting but are still demonstrably good for health.
“Not everyone is able, or feels able, to meet the recommendations of 150 minutes per week moderate to vigorous physical activity,” Spartano says. “But there is a large body of literature suggesting that small increases in physical activity can make a large impact on many health outcomes for people that are doing very little to start with.”
Spartano’s study falls short of establishing a causal link between light exercise and lower rates of dementia, but she hopes that her pattern will serve as a foundation for many more studies to come. Especially until more robust detection and treatment options are developed for dementia patients, she believes that making tiny lifestyle changes could be important for combating the disease. Exercise, at this point, may be a powerful weapon.
“We don’t have effective preventions or treatment solutions to address the growing public health crisis of climbing dementia rates,” Spartano says. “So focusing on lifestyle interventions, which have shown some potential benefit, are vital at this point.”
Design, Setting, Participants: Thi scross-sectional, community-based cohort study of the association of accelerometry-determined PA with brain MRI measures in Framingham, Massachusetts, included the Framingham Heart Study third-generation (examination 2, 2008-2011) and offspring (examination 9, 2011-2014) cohorts. Of 4021 participants who agreed to wear an accelerometer and had valid data (≥10 hours/day for ≥3 days), 1667 participants who did not undergo brain MRI (n = 1604) or had prevalent dementia or stroke (n = 63) were excluded. Data analysis began in 2016 and was completed in February 2019.
Exposures: Physical activity achieved using accelerometry-derived total activity(steps per day) and 2 intensity levels (light intensity and moderate to vigorous intensity).
Main Outcomes and Measures: Differences in total brain volume and other MRI markers of brain aging.
Results: The study sample of 2354 participants had a mean(SD) age of 53(13) years, 1276(54.2%) were women, and 1099 (46.7%) met the PA guidelines. Incremental light-intensity PA was associated with higher total brain volume; each additional hour of light-intensity PA was associated with approximately 1.1 years less brain aging (β estimate, 0.22; SD, 0.07; P = .003). Among individuals not meeting the PA guidelines, each hour of light-intensity PA (β estimate, 0.28; SD, 0.11; P = .01) and achieving 7500 steps or more per day (β estimate, 0.44; SD, 0.18; P = .02) were associated with higher total brain volume, equivalent to approximately 1.4 to 2.2 years less brain aging. After adjusting for light-intensity PA, neither increasing moderate to vigorous PA levels nor meeting the threshold moderate to vigorous PA level recommended by the PA guidelines were significantly associated with total brain volume.
Conclusions and Relevance: Every additional hour of light-intensity PA was associated with higher brain volumes, even among individuals not meeting current PA guidelines. These data are consistent with the notion that the potential benefits of PA on brain aging may accrue at a lower, more achievable level of intensity or duration.