In this review, the authors included 19 controlled studies (17 randomised, 1 non-randomised, 1 cross-over) examining the effects of exercise on cognitive function in individuals at risk of or diagnosed with Alzheimer’s disease. Only studies that included an exercise-only intervention compared to a non-diet, non-exercise control group and reported pre- and post-intervention cognitive function measurements were included. The sample (N = 1,150) consisted of older adults (mean age 77, SD 7.5 years), predominantly women (71.1%), who had on average 9.2 (SD 4.3) years of education. Most of the studies included samples of individuals who were at risk of Alzheimer disease because they had mild cognitive impairment (64%; n = 732); another 1% were at risk because they had a parent diagnosed with Alzheimer disease (n = 17), and 35% had diagnosed Alzheimer disease (n = 396). Exercise training was performed, on average, for 3.4 (SD 1.4) days per week at moderate intensity with sessions lasting for 45.2 minutes (SD 17) for 18.6 weeks (SD 10 weeks). Most interventions consisted of aerobic exercise training (65%), with a smaller proportion consisting of a combination of aerobic and resistance training (35%). There was a significant effect of exercise training compared to controls on cognitive function (standardised mean difference (SMD) 0.47, 95% confidence interval (CI) 0.26 to 0.68). For aerobic exercise alone, the between-group effect size was larger (SMD 0.65, 95% CI 0.35 to 0.95). For the combination of aerobic and resistance exercise training the between-group effect size was no longer statistically significant (SMD 0.19, 95% CI -0.06 to 0.43). This meta-analysis provides support for the use of exercise training as a therapeutic modality to improve cognitive function in individuals at risk of or diagnosed with Alzheimer disease. Further studies should investigate physical activity or exercise in combination with other strategies to develop more targeted prevention and treatment options for Alzheimer disease.
Panza GA, et al. Can exercise improve cognitive symptoms of Alzheimer’s disease? J Am Geriatr Soc 2018;66(3):487-95