Staying physically active can help keep adults fit as they grow older, but, contrary to what some may think, it may not protect against mental decline, according to a new study.

“While participation in physical activity has been shown to have many health benefits for older adults, this study does not provide strong support that it protects against cognitive decline,” said study author Dr. Maureen T. Sturman, of Rush University Medical Center in Chicago, Illinois.

Previous researchers have reported that physical activity may help guard against stroke and coronary heart disease, both of which may be associated with the development of dementia. Other studies have looked at the influence of physical activity on mental status and mental decline in old age, but such studies were either limited in their scope or had short follow-up times.

In the current study, Sturman and her team analyzed 1993 to 2003 data from the Chicago Health and Aging Project, a large ongoing study of risk factors for chronic disease among elderly adults. The 4,055 study participants, aged 73.5 years, on average, were black and white seniors who lived in the community. They were followed-up for about six years, during which they participated in periodic assessments of their mental health.

On average, the seniors engaged in nearly four hours of physical activity each week, the report indicates. Slightly more than half reported walking for exercise, more than a third reported gardening or doing yard work, and about a quarter said they participated in calisthenics or general exercise, the researchers report in this month’s Archives of Neurology.

Such physical activity did not appear to be associated with higher mental function at the start of the study, however. Further, although increased hours of physical activity appeared to be associated with slower rates of mental decline, this association did not hold true when the seniors’ participation in mentally stimulating activities was taken into consideration, the report indicates.

“It may be that those older individuals who participate in physical activity are also more likely to participate in cognitively stimulating activities,” Sturman speculated. “This study suggests it is important to account for the cognitive component of leisure activities to better understand the role of physical activity on cognition for older adults,” she added.

Also, Sturman and her colleagues note, lifetime participation in physical activity may be the key to preserving mental function in old age, rather than current activity levels, as was measured in this study.

“In summary, although physical activity has been shown to have many favorable effects on health, the results of this study do not provide strong support that it is inversely related to cognitive decline associated with aging,” they conclude.

Put simply, “for older adults, physical activity alone may not protect against cognitive decline,” Sturman told Reuters Health.

SOURCE: Archives of Neurology, November 2005.