Background: Delaying the development of Alzheimer disease by even one year would have a major global impact on the incidence of the illness. Studies of medications purported to slow cognitive decline have been equivocal. Physical activity has been associated with later onset of dementia and better cognitive function; however, this association has not been definitively proven in randomized trials. Lautenschlager and colleagues studied the effects of physical activity on cognitive decline.

The Study: The randomized controlled trial included persons 50 years and older who had self-reported memory problems. Participants with severe dementia, depression, heavy drinking, limited life expectancy, and mental illness were excluded. Baseline cognitive function and activity level were determined for all participants.

The primary outcome measure was scored on the cognitive section of the Alzheimer Dementia Assessment Scale (ADAS-Cog). This included measures of memory, language, and praxis. Secondary outcome measures included performance on several other tests, as well as word recall and verbal fluency. Depression and quality-of-life measures were monitored throughout the study.

Patients were randomized to a physical activity program or usual care. Research staff was blinded to the study groups. All participants received health-related educational material. The physical activity group was also encouraged to engage in three, 50-minute sessions of moderate activity (e.g., walking, other aerobic activity, strength training) per week. Those who were already physically active were asked to increase their activity by one, 50-minute session per week. The intervention lasted 24 weeks, and patients were reassessed at six, 12, and 18 months.

Results: Of the 311 participants in the initial pool, 170 were included in the primary analysis (85 persons in each group). After six months, the intervention group had higher ADAS-Cog scores than the control group. The intervention group improved scores by 0.26 points (95% confidence interval [CI], −0.89 to 0.54), whereas the control group decreased scores by 1.04 points (95% CI, 0.32 to 1.82); P = .04. Modest differences in ADAS-Cog scores persisted for the remainder of the follow-up period. More complete analyses confirmed these findings and showed comparatively better delayed recall and lower Clinical Dementia Rating scores in the intervention group. As expected, patients in the intervention group were more active than those in the control group, with 78.2 percent adherence to the prescribed activity at 24 weeks. The intervention group continued to perform more physical activity than the control group, although the difference declined over time.

Conclusion: This study showed that moderate physical activity leads to improved cognitive function in patients with self-reported memory problems and in those with documented mild cognitive impairment. The mechanism of improved cerebral perfusion may be one explanation for these benefits of exercise. The authors note that although physical activity is said to improve well-being, this was not shown in the current study and, therefore, is unlikely to be a confounding factor.