The Relationship Between Physical Activity and Executive Control Functioning as Modified by Genotype

Abstract

As we age, the structure of the brain deteriorates and cognitive functioning declines. The region of the brain that begins to age the fastest is the frontal lobe, in which the dorsal-lateral prefrontal cortex is involved in executive control functions such as planning, organizing, initiating behaviors, and working memory. For some individuals, the brain declines more rapidly with age because of genetic factors. Apolipoprotein E (APOE) is a gene that assists in the transport of cholesterol and repair of the brain when it is damaged. Presence of the ε4 allele impairs cholesterol transport and puts its carriers at risk for increased cognitive decline and possibly dementia of the Alzheimer's type (DAT). Physical activity can slow the aging process of the brain and delay the onset and severity of cognitive decline and DAT as it increases oxygenation and blood flow, neuronal growth and synaptogenesis, and it increases the expression of genes helpful to the functioning of the brain such as brain-derived neurotrophic factor (BDNF). Therefore, individuals at greater genetic risk for age-related cognitive decline (i.e., ε4 carriers) should receive increased benefit from physical activity. Accordingly, this study examined the relationship between physical activity and executive control functioning, assessed by the Wisconsin Card Sort Test (WCST) in middle-aged APOE ε4 carriers and non-carriers. High-active participants were predicted to perform better than their low-active counterparts, and this difference should be even greater among APOE ε4 carriers. While most research studies on this topic have focused on general cognitive performance, the present study is specific in its focus on executive control functioning. Sixty-seven cognitively normal middle-aged adults between the ages of 50 - 70 years were assessed on medical history, overall cognitive functioning, APOE genotype, level of physical activity, and executive control functioning (WCST). Using hierarchical regression, seven WCST variables were regressed on age, genotype, physical activity, and the interaction between genotype and physical activity. Analysis revealed that as level of physical activity increased, performance significantly improved on all seven WCST variables for APOE ε4 carriers, but not for non-carriers. These results reveal that the benefits of physical activity to cognitive performance in this age group are specific to those who are genetically at-risk for cognitive decline.