Adults with memory problems who participated in a home-based physical activity program experienced a modest improvement in cognitive function, compared to those who did not participate in the program, according to a study in the September 3 issue of JAMA.

As the world population ages, the number of older adults living with Alzheimer disease (AD) is estimated to increase from the current 26.6 million to 106.2 million by 2050. "If illness onset could be delayed by 12 months, 9.2 million fewer cases of AD would occur worldwide. For this reason, attempts have been made to identify individuals who are at increased risk of AD and to test interventions that might delay the progression of prodromal symptoms [early non-specific symptom, or set of symptoms] to full-blown dementia," the authors write.

Nicola T. Lautenschlager, M.D., of the University of Melbourne, Australia, and colleagues conducted a randomized controlled trial to test whether a physical activity intervention would reduce the rate of cognitive decline among 138 adults age 50 years and older at increased risk of dementia. The participants, who reported memory problems but did not meet criteria for dementia, were randomly allocated to an education and usual care group or to a 24-week home-based program of physical activity.

The aim of the intervention was to encourage participants to perform at least 150 minutes of moderate-intensity physical activity per week, which participants were asked to complete in three 50-minute sessions each week. The most frequently recommended type of activity was walking. The intervention resulted in 142 minutes more physical activity per week or 20 minutes per day than with usual care. Cognitive function was assessed with the Alzheimer Disease Assessment Scale–Cognitive Subscale (ADAS-Cog; a measuring tool that consists of a number of cognitive tests) over 18 months.

The researchers found that by study end, participants in the exercise group had better ADAS-Cog scores and delayed recall than those in the usual care control group. Participants in the physical activity group also had lower Clinical Dementia Rating scores than those in the usual care group.

"To our knowledge, this trial is the first to demonstrate that exercise improves cognitive function in older adults with subjective and objective mild cognitive impairment. The benefits of physical activity were apparent after 6 months and persisted for at least another 12 months after the intervention had been discontinued. The average improvement of 0.69 points on the ADAS-Cog score compared with the usual care control group at 18 months is small but potentially important when one considers the relatively modest amount of physical activity undertaken by participants in the study," the authors write.

"Unlike medication, which was found to have no significant effect on mild cognitive impairment at 36 months, physical activity has the advantage of health benefits that are not confined to cognitive function alone, as suggested by findings on depression, quality of life, falls, cardiovascular function, and disability."

In an accompanying editorial, Eric B. Larson, M.D., of the Group Health Center for Health Studies, Seattle, comments on the findings regarding exercise and cognitive function.

"Health advances of the past century have led to more individuals surviving to extreme old age, when their risk of Alzheimer disease and related dementias increases substantially. Exercise—and possibly other lifestyle factors—appear to affect vascular risk and late-life brain health. In addition to traditional medical approaches to prevent this dreaded disease, social factors such as providing universal education, general medical care, a suitable environment, adequate nutrition, habitual exercise, and opportunities for continued social interactions throughout the lifespan also may contribute significantly to improve well-being in late life."