Good Physical Fitness Counteracts Deleterious Effect Of Aging On Executive Functions: A Cross-sectional Study

Abstract

Physical activity level and cardiorespiratory fitness have been identified as positive moderators of aging on cognitive performance (Hillman et al., 2008). The meta-analysis of Colcombe and Kramer (2003) showed that this effect is larger for executive functions than for other functions such as information processing speed. Factorial analyses conducted by Miyake and his collaborators (2000) suggested however that at least three distinct executive functions can be separated: behavioral inhibition, updating of working memory and cognitive flexibility. PURPOSE: To determine the selectivity of positive effect of physical activity on three executive functions. METHODS: Three groups of sixteen volunteer participants performed a battery of eight cognitive tasks involving executive functions. Group A included young adults (Mean age = 23.56 years), group B sedentary older adults (Mean age = 69.25 years) and group C active older adults regularly practicing swimming (Mean age = 69.13 years). Stop task, Stroop task and random number generation task were used to tap behavioral inhibition, spatial running-span task and letter running-span task for updating of working memory and Wisconsin card sorting test and two switching tasks for cognitive flexibility. Physical activity level was assessed through the Dijon Physical Activity Questionnaire whereas cardiorespiratory fitness was estimated thanks to the Rockport one mile test. RESULTS: A first series of independent two-sample t-tests showed that younger adults performed significantly better than sedentary older adults in the eight tasks tapping executive functions. A second series of t-tests showed that older swimmers performed better than sedentary older adults in five tasks out of eight. In some cases, we did not observe any significant difference between younger adults and old swimmers. CONCLUSION: A regular practice of swimming counteracts the deleterious effect of aging on the three executive functions indentified by Miyake and coworkers (2000). Because of the cross-sectional design, we cannot reject another explanation: older swimmers would regularly practice physical activity because their executive functions perform well whereas sedentary older adults wouldn't because of failure in executive functions.