Staying mentally sharp is aging Americans’ highest priority, according to the National Council on Aging. While thousands of clinical trials suggest that physical exercise can protect or improve brain health as we age, few studies provide practical, prescriptive guidance for how much and what kind of exercise.
Now, an exhaustive systematic review of 4,600 clinical trials provides insight into the optimal dose of exercise—what kind and how much—for maintaining cognitive performance in healthy older adults, as well as those with mild cognitive impairment and dementia.
The review was led by Harvard Medical School researchers at the Berenson-Allen Center for Noninvasive Brain Stimulation at Beth Israel Deaconess Medical Center and published online May 30 in Neurology Clinical Practice.
“While there is solid evidence to suggest that maintaining a regular exercise regimen can improve brain health, we were most interested in how we could practically apply these scientific findings to the lives of our patients, their family members and even to ourselves,” said corresponding author Joyce Gomes-Osman, a postdoctoral research scholar at the Berenson-Allen Center and an assistant professor at the University of Miami Miller School of Medicine.
“For other forms of treatments such as prescription drugs, patients are prescribed a specific amount. Our study highlights the need to get this specific with exercise, too,” Gomes-Osman said.
The team found that nearly any type of exercise—including aerobic exercises, resistance training and mind-body exercises such as yoga and tai chi—can contribute to improved cognitive performance.
Interventions that had individuals exercising for at least 52 hours over a period of six months led to the greatest improvement in thinking abilities.
“For other forms of treatments such as prescription drugs, patients are prescribed a specific amount. Our study highlights the need to get this specific with exercise, too,” Gomes-Osman said.
Additionally, the most stable improvements in thinking abilities were found in mental processing speed, both in healthy older adults and individuals with mild cognitive impairment.
“It’s very encouraging that the evidence supports all sorts of different exercise interventions, not just aerobic, to improve thinking abilities,” said Alvaro Pascual-Leone, HMS professor of neurology and chief of the Division of Cognitive Neurology at Beth Israel Deaconess and director of the Berenson-Allen Center.
To conduct the review, Pascual-Leone, Gomes-Osman and colleagues searched the medical literature for randomized controlled trials testing the impact of various exercise regimens on cognition. The initial effort yielded 4,600 relevant studies. After screening those for quality and content, 98 trials, encompassing more than 11,000 participants, were included in the review.
Taken together, the studies investigated a wide range of exercises and duration of investigation, from as little as four weeks to as long as a year.
Using a rigorous review process, the researchers averaged and described the parameters used across the studies, revealing the relationships among exercise type, intensity, session duration, frequency and total hours and five categories of cognitive abilities.
Gomes-Osman notes that exercising for a certain number of minutes per week—well-known to confer cardiovascular and other physical health benefits—was not correlated with improved cognitive abilities, even though exercising for a certain number of hours over a period of months led to cognitive improvements. This suggests people need more consistent exercise over a longer period of time to achieve benefits in cognitive performance, she said.
“We are still learning about all the ways in which exercise changes our brain, and we are also all different, so identifying an ideal exercise dose remains a challenge,” said Gomes-Osman. “We have many more questions about exercise dose, and we will design further studies to follow up.”
This work was supported by the Evelyn McKnight Brain Institute and the Fundacao de Apoio a Pesquisa do Estado De Alagoas. Additional support came from the Sidney R. Baer Jr. Foundation, the National Institutes of Health (grants R01 MH100186, R01 HD069776, R01 NS073601, R21 MH099196, R21 NS085491, R21 HD07616) and Harvard Catalyst | The Harvard Clinical and Translational Science Center (NCRR and NCATS UL1 RR025758).
