Effect of physical exercise on popular measures of executive function in older, nonclinical, participants of...

Epidemiological studies have found that more physically active older participants have a reduced risk of Alzheimer disease. Based on enriched environment animal models, this effect is considered to result from physical exercise-induced molecular brain changes. This hypothesis has been tested in humans with randomized controlled trials involving physical exercise vs. more sedentary interventions with neuropsychological outcome measures. Fifty-one such randomized controlled trials were identified from Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines with keywords related to physical activity, cognition, and aging supplemented with reference list search. The five most popular executive function measures (each used in ≥8 trials) were meta-analyzed. Digit symbol was the only measure with a significant estimated overall effect size, indicating that physical exercise had a small (0.17) positive effect on change scores. Estimated overall effect sizes for physical exercise on Digit Span backward, Trails B, letter fluency, and Stroop Color-Word Interference time with/without correction were all not significantly different from zero. These results provide weak support for the notion that physical exercise produces molecular brain changes that enhance executive function test scores in older, nonclinical, participants.