Aerobic exercise training improved cognition in adults, even in those young and middle-age, a randomized clinical trial found.
Executive function improved significantly in adults ages 20 to 67 years, with older people seeing greater improvements (β 0.018 SD/y; P=0.028), reported Yaakov Stern, PhD, of Columbia University in New York City, and colleagues, in Neurology.
At age 40, executive function increased by 0.228 SD (95% CI 0.007–0.448); at age 60, it increased by 0.596 SD (95% CI 0.219–0.973).
“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,” Stern said in a statement.
Most research about exercise and cognition has focused on elderly patients, Stern noted, and those studies that included younger adults were small and lacked a control group.
In this trial, Stern and colleagues randomly assigned 132 sedentary, cognitively intact individuals with below median aerobic capacity to either an aerobic exercise training program or a control program of stretching and core-strengthening exercises for 6 months. The groups were equally balanced for sex (about 70% women) and age (median age 39 for the aerobic group and 37 for controls), and did not differ at baseline in education, estimated IQ, or any cognitive outcome measures.
All participants worked out at one of five New York City YMCA fitness centers. For the first 2 weeks, they trained at 55-65% of their maximum heart rate, gradually increasing intensity so that in weeks 5-26, they exercised at 75% of their maximum heart rate. Participants in the aerobic group chose any form of exercise they wanted, as long as they reached target heart rates. Of the 132 participants, 94 completed the 6-month intervention.
At 6 months, executive function improved significantly in the aerobic exercise group; that effect was moderated by age. After controlling for age and baseline performance, individuals with at least one APOE e4 allele showed less improvement in executive function with aerobic exercise (β 0.5129, 95% CI 0.0381–0.988; P=0.0346). Processing speed, language, attention, or episodic memory did not improve for participants of any age.
Aerobic exercise training also was associated with significantly increased cortical thickness in the left caudal middle frontal cortex on MRI. The increase was not linked to age and did not correlate directly with a corresponding change in any cognitive domain.
Aerobic capacity increased significantly (β 2.718; P=0.003) and body mass index (BMI) decreased significantly (β −0.596; P=0.013) in the aerobic exercise group, but not in controls.
Interestingly, older adults in this study appeared to benefit more from aerobic exercise than their younger counterparts, observed James Blumenthal, PhD, of Duke University Medical Center in Durham, North Carolina, who was not involved with the research.
“The mechanisms responsible for the improvement in executive function are unclear, although improved aerobic fitness apparently mediated the improvements among those who completed the aerobic exercise intervention,” Blumenthal told MedPage Today. “However, because participants in the aerobic exercise condition also lost more weight, it is unclear whether improved aerobic capacity or weight loss may have contributed to the observed improvements in executive function.”
Studies of older adults, including the ENLIGHTEN trial which Blumenthal led, also showed that aerobic exercise had a beneficial effect on executive function, but not language or memory.
“Executive function usually peaks around age 30,” Stern said. “I think that aerobic exercise is good at rescuing lost function, as opposed to increasing performance in those without a decline.”
The researchers noted several limitations to the study, including the small sample size. Future studies should assess whether the effects of exercise can be sustained over longer periods of time, the team added.
The study was supported by the National Institutes of Health.
The researchers reported relationships with Eli Lilly, Axovant, Takeda, AbbVie, Apos-Therapy, Inc., LIH Medical, Everest Foundation, and the California Walnut Commission.