A report published this week in the Annals of Internal Medicinesuggests that moderate levels of exercise may delay the onset of dementia. The study, which spanned 11 1/2 years, showed a remarkable 38% reduction in the chance of getting dementia for people who exercised three or more times a week, in comparison with those who exercised less than three times a week.
The study was extensive, involving 1,740 participants. To ensure that none of the participants showed any signs of dementia going into the study, they were given cognitive screening tests, and only the top 25 percent were accepted. Each participant was followed up every two years for an average of 6.2 years over the course of the study. By the end of the study, 158 people developed some form of dementia (107 of those developed Alzheimer’s Disease) and 1,185 remained dementia-free. Others either withdrew from the study or died during that period.
The findings support recent studies that suggest physical exercise can enhance cognitive function. Of those who exercised three or more times per week, an average of 13 people out of 1000 developed dementia in each year of the study. For those who exercised less, this ‘incident rate’ was 19.7 people out of 1000. Physical exercise was defined as lasting at least 15 minutes at a time and included such things as walking, hiking, bicycling, aerobics, swimming, weight training, and stretching.
Other factors were considered as well, such as smoking, drinking, using dietary supplements, as well as health conditions such as coronary heart disease, cerebral-vascular disease, hypertension, and diabetes. Surprisingly, these factors, along with gender and age differences were fairly consistent across the two groups: those with dementia and those without. In other words, the single most important difference was the frequency of exercise.
The researchers did not set out to determine a dose-response, that is, the amount of exercise needed to have a beneficial effect. But they did determine that the greatest reduction was in those who scored lower on fitness tests, as long as they exercised at least three times a week. Another study done a year earlier showed that moderate levels of physical activity (3-5 times per week) were associated with a greater delay in the onset of dementia than high exercise levels (more than 7 times per week)– a 45% reduction compared with a 28% reduction . This may mean that one only needs to do moderate amounts of exercise to realize these benefits, and that the frailest people are the most likely to see the benefits. The chief author of the article suggests that senior citizens may have even more reason to “use it even after (they) are losing it”
The researchers note that they did not take into consideration non-leisure and work activities of the participants, which may affect the results. But the results of the study are consistent with earlier ones which showed less tissue loss in the hippocampus in persons at higher levels of physical functioning than frailer older adults. The hippocampus is an area of the brain involved in cognitive functions and is damaged in Alzheimer’s patients.
The researchers concluded the study by suggesting that “physicians and health promotion programs might find this information valuable as our society works to find truly effective ways to promote physical activity for all its well-known benefits”. It would do society well to look into preventative measures such as exercise to help decrease the incidence of Alzheimer’s and other forms of dementia. This would allow seniors to live out their final years as independently as possible and curb what is often referred to as the greatest fear of aging.
To your health,
Larson, E.B., Wang, L., Bowen, J.D. et al (2006). Exercise is associated with reduced risk for incident dementia among persons 65 years of age and older. Annals of Internal Medicine,144, 1-20.
Brown, D.W., Brown, D.R., Heath, G.W. et al (2004). Associations between physical activity dose and health-related quality of life. Medicine & Science in Sports & Exercise,36:890-896.
Colcombe, S.J. Erickson, K.I., Raz, N. et al (2003). Aerobic fitness reduces brain tissue loss in aging humans. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences58:M176-M180.