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Aerobic exercise may mitigate age-related cognitive decline



Among adults with below-average fitness, aerobic exercise significantly improves executive function, according to a randomized clinical trial published in Neurology.

Yaakov Stern, PhD, chief of cognitive neuroscience in the department of neurology at Columbia University Chris Leary

Dr. Yaakov Stern

“The effect of aerobic exercise on executive function was more pronounced as age increased, suggesting that it may mitigate age-related declines,” wrote Yaakov Stern, PhD, chief of cognitive neuroscience in the department of neurology at Columbia University, New York, and his research colleagues.

Research indicates that aerobic exercise provides cognitive benefits across the lifespan, but controlled exercise studies have been limited to elderly individuals, the researchers wrote. To examine the effects of aerobic exercise on cognitive function in younger, healthy adults, they conducted a randomized, parallel-group, observer-masked, community-based clinical trial. The investigators enrolled 132 cognitively normal people aged 20-67 years with aerobic capacity below the median. About 70% were women, and participants’ mean age was about 40 years.

“We hypothesized that aerobic exercise would have cognitive benefits, even in this younger age range, but that age might moderate the nature or degree of the benefit,” Dr. Stern and his colleagues wrote.

Participants were nonsmoking, habitual nonexercisers with below-average fitness by American Heart Association standards. The investigators used baseline aerobic capacity testing to establish safe exercise measures and heart rate targets.

The investigators randomly assigned participants to a group that performed aerobic exercise or to a control group that performed stretching and toning four times per week for 6 months. Outcome measures included domains of cognitive function (such as executive function, episodic memory, processing speed, language, and attention), everyday function, aerobic capacity, body mass index, and cortical thickness.

During a 2-week run-in period, participants went to their choice of five YMCA of New York City fitness centers three times per week. They had to attend at least five of these sessions to stay in the study. In both study arms, training sessions consisted of 10-15 minutes of warm-up and cooldown and 30-40 minutes of workout. Coaches contacted participants weekly to monitor their progress, and participants wore heart rate monitors during each session. Exercises in the control group were designed to promote flexibility and improve core strength. In the aerobic exercise group, participants had a choice of exercises such as walking on a treadmill, cycling on a stationary bike, or using an elliptical machine, and they gradually increased their exercise intensity to 75% of maximum heart rate by week 5. A total of 94 participants – 50 in the control group and 44 in the aerobic exercise group – completed the 6-month trial.

Executive function, but not other cognitive measures, improved significantly in the aerobic exercise group. The effect on executive function was greater in older participants. For example, at age 40 years, the executive function measure increased by 0.228 standard deviation units from baseline; at age 60, it increased by 0.596 standard deviation units.

In addition, cortical thickness increased significantly in the aerobic exercise group in the left caudal middle frontal cortex Brodmann area; this effect did not differ by age. Improvement on executive function in the aerobic exercise group was greater among participants without an APOE E4 allele, contrasting with the findings of prior studies.

“Since a difference of 0.5 standard deviations is equivalent to 20 years of age-related difference in performance on these tests, the people who exercised were testing as if they were about 10 years younger at age 40 and about 20 years younger at age 60,” Dr. Stern said in a press release. “Since thinking skills at the start of the study were poorer for participants who were older, our findings suggest that aerobic exercise is more likely to improve age-related declines in thinking skills rather than improve performance in those without a decline.”

Furthermore, aerobic exercise significantly increased aerobic capacity and significantly decreased body mass index, whereas stretching and toning did not.

“Participants in this trial scheduled their exercise sessions on their own and exercised by themselves,” the authors noted. “In addition, they were allowed to choose whatever aerobic exercise modality they preferred, so long as they reached target heart rates, enhancing the flexibility of the intervention.” Limitations of the study include its relatively small sample size and the large number of participants who dropped out of the study between consenting to participate and randomization.

The trial was funded by the National Institutes of Health. Dr. Stern reported receiving a grant from the California Walnut Commission and consulting with Eli Lilly, Axovant Sciences, Takeda, and AbbVie. A coauthor reported grant support from AposTherapy, LIH Medical, and the Everest Foundation.

SOURCE: Stern Y et al. Neurology. 2019 Jan 30. doi: 10.1212/WNL.0000000000007003.

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