Dementia is a condition that results in impaired memory and thinking severe enough to disrupt daily life. About 10% of Americans older than 65 have some degree of dementia. Since dementia is not curable, or even very treatable, researchers are looking for ways to reduce its risk. One proposed strategy, regular exercise, has shown promise in some studies.

In an article published in the January 17, 2006 issue of the Annals of Internal Medicine , researchers report that older people who exercise three times per week or more are significantly less likely to develop dementia than those who are less active.

About the Study

The researchers followed 1,740 people for an average of six years. The participants were ages 65 or older and had no evidence of dementia when the study began (i.e., they scored in the upper 25th percentile on a cognitive function test). When they entered the study, the participants reported how many times they exercised (e.g., walked, biked, swam) for 15 minutes or more at a time each week. The researchers evaluated the participants every two years to determine if they had developed dementia.

During the study, 158 participants developed dementia. After adjusting for factors associated with the risk of developing dementia (e.g., diabetes, blood pressure, heart disease), the researchers found that the participants who exercised three times per week or more were 32% less likely to develop dementia than those who exercised less.

These results should be interpreted with some caution, because exercise frequency was measured by self-report, and participants may have tended to over-report the amount of exercise they do.

How Does This Affect You?

Do these findings prove that exercising regularly can help prevent dementia? Not quite. As the authors of an accompanying editorial point out, it is possible that people who exercise are more engaged in life in general, which may help decrease their risk for dementia. Future studies will better define the association between exercise and the onset of dementia, as well as the optimal frequency, intensity, and duration of exercise required to help prevent dementia.

But this study does suggest that preventing or delaying the onset of dementia may be yet another benefit of regular exercise in older people. No matter what your age, regular exercise can help reduce your risk of heart disease, diabetes, certain cancers, and possibly even Alzheimer’s disease and other forms of dementia. Aim to get at least 30 minutes of exercise on most days of the week.