According to a new study published this week regular exercise can slow down the onset of dementia and Alzheimer's disease.
The study by the University of Washington, is the most definitive investigation of exercise and dementia to date, and says that even elderly people who did modest amounts of gentle exercise, such as walking for 15 minutes three times a week, appeared to benefit.
It also found that the more frail a person is, the more he or she may benefit from exercise.
According to Eric B. Larson, the director of Group Health Cooperative's Center for Health Studies and the lead investigator for the study, the findings indicate that exercise may slow the progression of age-related problems in thinking.
The study followed 1,740 Group Health members, aged 65 and older over a six-year period.
The researchers contacted the participants every two years to assess factors potentially affecting dementia, including exercise frequency, cognitive function, physical function, symptoms of depression, and lifestyle characteristics.
After six years, 158 participants had developed dementia and 107 of those with dementia had been diagnosed with Alzheimer's disease.
People who exercised three or more times a week had a 30 percent to 40 percent lower risk for developing dementia compared with those who exercised fewer than three times per week.
Larson's study was intentionally designed to be more definitive than previous research into exercise and dementia as many of those results have been mixed.
In his study, Larson's team used tests scores to ensure that all participants had a minimum level of function at the time the study began.
This effectively eliminated participants who might already be developing Alzheimer's disease, but not showing overt signs of the disease.
That factor that would have made it difficult to determine the true effects of exercise over the duration of the study.
Larson believes that exercise may improve brain function by boosting blood flow to areas of the brain used for memory.
His theory is supported by earlier research which has shown that poor blood flow can damage these parts of the brain.
He suggests that exercise may prevent damage and might even help repair these areas by increasing blood flow.
Larson says it is never too late to begin exercising, and even at 75 a person can still benefit by starting to exercise.
He says simply walking or swimming for 15 minutes three times a week may be enough.
He recommends programs such as the "EnhanceFitness" classes that Group Health offers to its Medicare Advantage members because they are designed with attention to senior safety issues, such as avoiding falls.
In conclusion Larson says that as the population ages, strategies are needed to reduce the risks and delay the onset of debilitating disorders such as Alzheimer's disease.
The findings, he says, indicate that programs that encourage elderly people to exercise should be part of those strategies.
The study appears in the January 17 issue of Annals of Internal Medicine.