Exercise Beneficial For Individuals At Risk Of Dementia
Alzheimer disease (AD) affects 26.6 million people worldwide and is expected to affect 106.2 million by 2050 as the world population increases. Nicola T. Lautenschlager, M.D. (University of Melbourne, Australia) and colleagues write that, "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."
To test the impact of physical activity on the rate of cognitive decline, Lautenschlager and colleagues conducted a randomized controlled trial that consisted of 138 adults age 50 years and older who were at increased risk of dementia. Randomization created two groups of participants: one group was assigned to education and usual care and the second was assigned to a 24-week home-based program of physical activity. All participants reported memory problems but did not meet criteria for dementia.
The exercise intervention encouraged patients to perform at least 150 minutes of moderate-intensity physical activity per week that were to be completed in three weekly 50-minute sessions. Walking was the activity most frequently recommended, and the intervention in general resulted in more physical activity per week than with usual care - about 142 minutes per week or 20 minutes per day. The researchers used the Alzheimer Disease Assessment Scale-Cognitive Subscale (ADAS-Cog, a battery of tests) to assess cognitive function over an 18-month period.
At the end of the study, participants who were randomly assigned to the exercise group were found to have better ADAS-Cog scores and delayed recall scores compared to participants who were assigned to the control (usual care) group. In addition, Clinical Dementia Rating scores were lower in the physical activity group compared to 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," write the researchers.
Lautenschlager and colleagues conclude: "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."
Eric B. Larson, M.D. (Group Health Center for Health Studies, Seattle) writes in a comment accompanying the research that:
"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."
Effect of Physical Activity on Cognitive Function in Older Adults at Risk for Alzheimer Disease: A Randomized Trial
Nicola T. Lautenschlager; Kay L. Cox; Leon Flicker; Jonathan K. Foster; Frank M. van Bockxmeer; Jianguo Xiao; Kathryn R. Greenop; Osvaldo P. Almeida
JAMA (2008). 300: pp. 1027 - 1037.
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