Optimal Exercise Dose for Better Cognition Determined

Damian McNamara

June 01, 2018

The optimal dose of exercise for improved cognition in older adults is suggested by a new systematic review.

Building on numerous studies showing a positive relationship between regular exercise and improvements in brain health, researchers have determined that 52 hours over 6 months is the minimum amount needed to improve cognition in older adults.

In fact, total exercise time was the most important factor linked to improved processing speed and attention, executive function, and global cognition in a systematic review of 98 randomized controlled trials. This finding suggests that cognitive improvements associated with exercise act on the same constructs affected by cognitive aging.

Exercising in approximately 1-hour sessions to reach this total was associated with improved cognitive performance in older healthy adults, those with mild cognitive impairment, and others with dementia.

Interestingly, researchers report that cardiovascular exercise, resistance training, and mind-body exercises, or a combination of these, were advantageous. Running might work for some people, but patients with a bad hip or bad knee could still see benefit from lower-impact activities, such as yoga or tai-chi, study author Joyce Gomes-Osman, PT, PhD, assistant professor of clinical physical therapy and neurology at the University of Miami Miller School of Medicine in Florida, told Medscape Medical News.

"We were interested in finding practical advice that is evidence-based," she said.

The systematic review, published online May 30 in Neurology Clinical Practice, included 11,061 adults with a mean age of 73 years.

Older healthy adults represented 59% of the total population; another 26% had mild cognitive impairment and 15% had dementia based on Mini-Mental State Examination or similar measure scores.

Researchers compared cognition and memory between participants who exercised at least 4 weeks and others who did not start a new exercise regimen. In contrast to benefits reported at 52 hours, people who exercised an average of 34 total hours over the 6 months did not show improved cognitive skills.

Only total exercise time was associated with cognitive improvement in a bivariate analysis; session time in minutes, exercise frequency per week, and total number of weeks of exercise did not correlate with improved thinking skills.

"I was very surprised by that finding. Before coming in I had my bet set on weekly minutes," Gomes-Osman said.  

In contrast, exercise recommendations from the American Heart Association, the US Department of Health and Human Services and the American College of Sports Medicine are formulated in weekly minutes. These organizations promote 150 minutes of moderate exercise or 75 minutes of vigorous exercise per week, for example. The current findings suggest a longer-term program may be necessary to see cognitive benefits from exercise, she added.

Calculating a recommended exercise "dose" might help, she added. "Less than 40 percent of Americans 65 and older meet the 150 minute/75 minute guidelines and 20% are absolutely sedentary."

When asked if a goal of 52 hours over 6 months would motivate behavior change in patients, Gomes-Osman replied that it might be useful for patients to think of exercise like a point system. "Maybe it doesn't matter [for brain health] if you do 30 minutes or 45 minutes a day, or you exercise twice a week or three times a week. But it's good for people to have an idea when they can see an outcome."

She added that having a "ballpark figure" like 52 hours could motivate patients to continue exercising if they do not see any improvement after 1 month, for example.

"Our pitch as healthcare providers needs to change. Instead of saying, 'Go out and be active,' we need to explain what being active means and what they might do," she said.

Of note, 58% of participants were sedentary at the beginning of each study. Using exercise to combat sedentary behavior may be a reason why thinking skills improved, the researchers noted.

No beneficial effects on memory skills emerged in the systematic review.  

Gomes-Osman and colleagues are not the first researchers to look at exercise and brain health. More than 1000 clinical trials, 174 systematic reviews, and 50 meta-analyses have assessed the effects of exercise on cognition in older adults. Despite a consensus on the positive effects, "the available literature offers no practical prescriptive guidance for physical exercise to promote cognitive brain health," they write. "The sufficient and optimal exercise dose and regimen to induce such effects have not been fully examined."

When asked to comment on the findings by Medscape Medical News, James A. Hendrix, PhD, director of Global Science Initiatives at the Alzheimer's Association in Chicago, Illinonis, said, "It's a cool idea to put a dosage on exercise, the same way we put a dosage on medication."

"We are starting to think of exercise as a way to intervene," he said. However, the timing is also essential. "One thing we're learning from biomarker studies is our brains begin to change 10 to 20 years before the onset of the disease." For a 65-year-old starting to show signs of dementia, their brain may have started changing as early as age 45, he said. "So if you're concerned about Alzheimer's disease or have a history of Alzheimer's disease in your family, don't wait until symptoms appear."

"We also have to think about when we introduce this [exercise recommendation]," Gomes-Osman agreed.

Hendrix applauded the finding that many different types of exercise could be beneficial. Recommend that patients choose a type of exercise they enjoy "because it's easier to make it part of your lifestyle." Also, remind people to consult a doctor before starting a new exercise regimen.

"It's also important to recognize that this is a review article, not a double-blind, placebo-controlled study," he added.

The Alzheimer's Association U.S. Study to Protect Brain Health Through Lifestyle Intervention to Reduce Risk (US POINTER) is looking at whether lifestyle modifications can lower risks for cognitive decline. Researchers plan to evaluate whether physical exercise, nutritional counseling, and improved self-management of health and other factors can benefit cognition among 25000 volunteers in the 2-year clinical trial.

Gomes-Osman is actively recruiting older adults in South Florida to continue research in this area. "Exercise is effective, has very few side effects, and it's the best intervention we have right now."

The study was supported by a grant from the Evelyn McKnight Institute at the University of Miami Miller School of Medicine. Gomes-Osman and Hendrix have disclosed no relevant financial relationships.

Neurol Clin Pract. Published online May 30, 2018. Abstract

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