We've long known that regular exercise is good for us--it helps to reduce stress, maintain weight and lower the risk for heart disease, diabetes, hypertension, some cancers and osteoporosis. But with medical research regularly adding to the laundry list of health benefits, writing about it can take on the tone of a late-night informercial, "But wait, there's more."
The latest selling point comes from mounting evidence that physical activity can help prevent cognitive decline, most recently, two reports published in the Archives of Neurology. One study found that for middle aged or older individuals, moderate exercise appears to reduce the risk of mild cognitive impairment (MCI), while a six-month program of a high-intensity aerobic exercise program may improve cognitive functions in those who already have the condition. MCI is the state somewhere between the normal age-related, "what's his name again?" memory lapses and the personality changes and cognitive decline of dementia or Alzheimer's disease. Each year, 10 percent to 15 percent of individuals with mild cognitive impairment will develop dementia, as compared with 1 percent to 2 percent of the general population.
In one report, Yonas E. Geda, M.D., M.Sc., and colleagues at Mayo Clinic, Rochester, MN, studied 1,324 individuals without dementia who were part of the Mayo Clinic Study of Aging. Participants completed a questionnaire that detailed their history of exercise, and were assessed and classified as having normal cognition or mild cognitive impairment. Those who had engaged in moderate exercise during midlife, showed a 39 percent reduction in the odds of developing MCI, and moderate exercise in late life was associated with a 32 percent reduction.
In another article, Laura D. Baker, Ph.D., of the University of Washington School of Medicine and Veterans Affairs Puget Sound Health Care System, Seattle, and colleagues report the results of a randomized, controlled clinical trial involving 33 adults with mild cognitive impairment (17 women, average age 70). A group of 23 were randomly assigned to an aerobic exercise group and exercised at high intensity levels under the supervision of a trainer for 45 to 60 minutes per day, four days per week. The control group of 10 individuals performed supervised stretching exercises according to the same schedule but kept their heart rate low. Fitness testing, body fat analysis, blood tests of metabolic markers and cognitive functions were assessed before, during and after the six-month trial.A total of 29 participants completed the study. Overall, the patients in the high-intensity aerobic exercise group experienced improved cognitive function compared with those in the control group. These effects were more pronounced in women than in men, despite similar increases in fitness. The sex differences may be related to the metabolic effects of exercise, as changes to the body's use and production of insulin, glucose and the stress hormone cortisol differed in men and women.
Exercise promotes the production of nerve-protecting compounds, greater blood flow to the brain, improved development and survival of neurons and the decreased risk of heart and blood vessel diseases, which may explain why it promotes cognitive health. Then again, the authors notel, "A subject who engages in regular physical exercise may also show the same type of discipline in dietary habits, accident prevention, adherence to preventive intervention, compliance with medical care and similar health-promoting behaviors."
