April 16 (HealthDay News) -- Regular physical exercise may help protect against mild cognitive impairment, according to a Mayo Clinic study.

People with mild cognitive impairment can handle everyday activities but often have trouble remembering details of conversations, events and upcoming appointments. Most, but not all, people with mild cognitive impairment experience a progressive decline in their cognitive abilities, and the underlying cause is usually Alzheimer's disease, according to background information in the study.

The physical benefits of exercise are well-known, but this is one of the first studies to examine whether exercise can help protect the brain.

The Mayo researchers randomly selected 868 people, aged 70 to 89, taking part in the ongoing Mayo Clinic Study of Aging. Of these people, 128 had mild cognitive impairment, and 740 were cognitively normal. The researchers conducted surveys to gather data on the participants' levels of exercise between the ages of 50 and 65 and during the year prior to the survey.

Moderate physical exercise between the ages of 50 and 65 was associated with a reduced risk of cognitive impairment, but the same was not true of exercise during the year prior to the survey.

The study was expected to be presented Wednesday at the American Academy of Neurology annual meeting, in Chicago. Lead investigator and neuropsychiatrist Dr. Yonas Endale Geda said the findings need to be replicated in a prospective cohort study, and also noted that this study did not address how physical exercise may protect against mild cognitive impairment.

"Regarding the mechanism of action of physical exercise and mild cognitive impairment, we speculate that either exercise induces chemicals that protect brain cells, or exercise is simply a marker for an overall healthy lifestyle, or there is some positive interaction among exercise, healthy lifestyle and intellectually stimulating activity," Geda said in a prepared statement.

SOURCE: American Academy of Neurology, news release, April 16, 2008