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, 2008 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 Alzheimer disease 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." (JAMA. 2008;300[9]:1027-1037)

Editor's Note: Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

Editorial: Physical Activity for Older Adults at Risk for Alzheimer Disease 

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." (JAMA. 2008;300[9]:1078-1079).

About Cognitive Impairment

Mild cognitive impairment is a transitional stage between normal aging and dementia, according to background information in the article. Previous studies have found an association between mild cognitive impairment and diabetes. Poor blood glucose control over time may lead to neuron loss, and diabetes is associated with heart disease and stroke, which also may increase the risk of cognitive impairment.

About Alzheimer's Disease 

Alzheimer's disease (AD) is a slowly progressive disease of the brain that is characterized by impairment of memory and eventually by disturbances in reasoning, planning, language, and perception. Alzheimer's disease is the most common cause of dementia, which afflicts 24 million people worldwide. Alzheimer's disease is not a normal part of aging and is not something that inevitably happens in later life. It is rarely seen before the age of 65. The likelihood of having Alzheimer's disease increases substantially after the age of 70 and may affect around 50% of persons over the age of 85.

About Dementia 

Dementia is a progressive brain dysfunction (in Latin 'dementia' means irrationality), which results in a restriction of daily activities and in most cases leads in the long term to the need for care. Many diseases can result in dementia, the most common one being Alzheimer's disease .

The probability of suffering from dementia increases with advancing age. Dementia predominantly occurs in the second half of our life, often after the age of 65. The frequency of dementia increases with rising age from less than 2 % for the 65-69-year-olds, to 5 % for the 75-79 year-olds and to more than 20 % for the 85-89 year-olds. Every third person over 90 years of age suffers from moderate or severe dementia (Bickel, Psycho 1996, 4-8). About half of those affected by dementia suffer from Alzheimer's disease.