Almost any amount of moderate physical activity in mid- or late life reduced the odds of mild cognitive impairment by 30% to 40% in an ongoing cohort study, researchers reported.Men and women derived similar benefit, which was limited to moderate exercise — not light or vigorous physical activity, investigators wrote in the January Archives of Neurology.
“Our findings contribute to the growing body of literature that indicates the potentially beneficial relationship between physical exercise and cognition,” Yonas E. Geda, MD, of the Mayo Clinic in Rochester, Minn., and colleagues concluded. “A future population-based cohort study is needed to confirm whether physical exercise is associated with decreased risk of incident mild cognitive impairment.”
Meanwhile, a small, separate interventional study described in the same journal showed that six months of high-intensity aerobic exercise was associated with significant improvement in executive function in older women at increased risk of cognitive decline, but not in older men.
Mild cognitive impairment confers a five- to 10-fold increased risk of dementia compared with normal cognition. Observational studies have shown that physical activity may protect against dementia and Alzheimer’s disease, and some evidence suggests that exercise for individuals with mild cognitive impairment offers some protection, too, the authors wrote.
Geda and colleagues continued exploration of the association between physical activity and cognitive impairment with an evaluation of the effect of physical activity in midlife, approximately the age of onset for mild cognitive impairment. Data for the study came from the Mayo Clinic Study of Aging.
The study included 1,324 participants who completed a standardized questionnaire about physical activity. Their median age was about 80, and none of the participants exhibited signs of dementia at baseline.
Investigators assessed the frequency and intensity of physical activity as reported by each participant.
- Light exercise: bowling, leisurely walking, stretching, slow dancing, and golfing using a cart.
- Moderate exercise: brisk walking, hiking, aerobics, strength training, swimming, tennis doubles, yoga, martial arts, weight lifting, moderate use of exercise machines, and golfing without use of a cart.
- Vigorous exercise: jogging, backpacking, bicycling uphill, tennis singles, racquetball, skiing, and intense or extended use of exercise machines.
The neuropsychologic evaluation consisted of nine tests that assessed memory, executive function, language, and visuospatial skills.
A consensus panel classified each participant as having normal cognition (N=1,126) or mild cognitive impairment (N=198). The two groups differed significantly in several respects. Participants with mild cognitive impairment were more likely to be men, older, less educated, more likely to be depressed, and had more comorbidity (P<0.001 to P=0.02).
Any frequency of moderately intense activity in midlife (ages 50 to 65) was associated with an odds ratio of 0.61 for mild cognitive impairment (95% CI 0.43 to 0.88, P=0.008). Moderate activity in later life was associated with an odds ratio of 0.68 (95% CI 0.49 to 0.93, P=0.02).
More or less intense activity of any frequency or duration did not significantly affect the odds ratio for mild cognitive impairment.
The authors noted several limitations of the study, including a cross-sectional design than could not assess causality, self-reported physical exercise data and relatively few subjects engaged in vigorous exercise in late life, which limited statistical power for that analysis.
A prospective evaluation of high-intensity aerobic exercise for patients with existing mild cognitive impairment showed that women had improved executive function, but men did not.
The study involved 17 women and 16 men ages 55 to 85. All had mild cognitive impairment by standardized assessment criteria, and all reported sedentary lifestyles at enrollment, Laura D. Baker, PhD, of the Veterans Affairs Puget Sound Health Care System in Seattle, and colleagues reported.
Participants were randomized 2:1 to aerobic exercise or stretching activity (control) and followed for six months. Both groups engaged in their assigned, supervised activities four times a week for 45 to 60 minutes at each session.
After two weeks, activity was supervised once a week. Participants assigned to aerobic exercise increased the duration and intensity of exercise over the first six weeks until they reached 75% to 85% of heart rate reserve, a level maintained for the remainder of the study.
Cognitive function was assessed at baseline and after three and six months of follow-up, as were physical status and laboratory values.
The results showed overall improvement in executive function among aerobic exercisers (P=0.04). Including gender as a predictive variable in the statistical model revealed significant interaction, reflecting a difference in response to the intervention for men and women (P=0.04).
Aerobic exercise increased glucose disposal, and reduced fasting plasma levels of insulin, cortisol, and brain-derived neurotrophic factor in women, the researchers reported. Among men, aerobic exercise increased plasma levels of insulin-like growth factor I.
Women on aerobic exercise demonstrated improvement in all four assessments of executive function, while men showed improvement in only one test.
“Aerobic exercise is a cost-effective practice that is associated with numerous physical benefits,” the authors concluded. “The results of this study suggest that exercise also provides a cognitive benefit from some adults with mild cognitive impairment.”
They also noted several limitations, including small sample size, exclusion of a number of subjects for medical reasons, and the fact that “the demands of the aerobic intervention are suited for a controlled trial, but may not be well-tolerated in less structured, less supervised population-based studies.”
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