The relations between physical activity, executive function, and white matter integrity in older adults

The worlds population of older adults is steadily increasing as people begin to live longer (Murman, 2015). There is a need to examine lifestyle changes that may prevent or slow down age-related cognitive decline. Physical activity is associated with better cognitive function in older adults (Colcombe & Kramer, 2003), particularly better executive function (Angeveran et al., 2008; Smith et al., 2010; Sherder et al., 2014). There is reason to believe that white matter integrity may mediate these changes (Grieve et al., 2007; Daselaar et al., 2015). In the current study, level of physical activity and steps in healthy older adults was measured. Diffusion tensor imaging (DTI) was utilized to examine white matter integrity, and neuropsychological testing was used to examine level of executive functioning. Results indicated that average steps were significantly related to executive function (t=2.829, p=.007), while moderate to vigorous physical activity (MVPA) was not (t=1.772, p=.08). White matter integrity, measured globally and in regions-of-interest (ROIs) did not mediate the associations between MVPA or average steps and executive function. These results suggest that white matter integrity alone may not be the mechanism by which physical activity impacts executive function in healthy older adults, and future research should examine additional health risk factors that may contribute.