Keeping Active Will Lessen the Risk of Cognitive Impairment

Most of us in our senior years fear the onset of Alzheimer’s, which is usually heralded by a fall in cognitive function.  But two recent studies reported in the Archives of Internal Medicine show us there’s something we can do about it.

The first study analyzed data from the Women’s Antioxidant Cardiovascular Study (WACS).  These were women with cardiovascular disease or three cardiovascular risk factors – a category of people who are at high risk of cognitive decline.  Although the study showed no relationship between intake of antioxidant vitamins and cognitive function, the data collected was valuable in exploring the possible relationship of cognition to physical activity.  Over an 18-month period, more than 2,800 women in the study were assessed by telephone using a cognitive test battery that included 5 tests of global cognition, verbal memory, and category fluency.  Testing was done three more times over the next 5½ years.  Energy expenditure data were obtained from 2-yearly assessments of recreational physical activity.

Appropriate analyses showed there were decreasing rates of cognitive decline with increasing physical activity.  When the lowest 20% of physically active subjects were compared with the highest and the next-to-highest 20% groups, the difference in their activity was equivalent to brisk daily 30-minute walks, and the difference in their cognitive decline brought them to the level for women 5 to 7 years younger.

The second study employed data from the Health, Aging, and Body Composition (Health ABC) study, which involved a group of more than 3,000 men and women aged 70 to 80.  The investigators examined the relationship between exercise and cognitive impairment in a select sample of 197 persons who met strict eligibility criteria.  Physiological measurements of activity energy expenditure (AEE) were used to overcome the criticism often leveled at self-reports of exercise.  Cognitive function was measured using the Modified Mini-Mental State Examination (MMSE) at baseline and at 2 or 5 years; impairment was regarded as a decline of at least 9 points on a100-point scale. 

After appropriate adjustments for possibly biasing factors (gender, age, weight, sleep duration, diabetes, and general health), it was found that the subjects in the highest 1/3 of AEE had lower odds of developing cognitive impairment than those in the lowest 1/3 of AEE.  And there was a clear dose-response relationship between AEE and cognitive impairment.           

These aren’t the first studies to report the association between high levels of physical activity and postponement of cognitive impairment.  A prospective 24-week controlled trial from Australia, published in the Journal of the American Medical Association, is perhaps the most convincing evidence of a cause-and-effect in the relationship.  There’s now little excuse for well-informed seniors not to realize that regular physical activity can prevent or postpone the onset of cognitive decline, if it’s in their genes.