Effects of improved physical fitness on cognitive/psychological functioning in community-dwelling, sedentary middle-aged and older adults

A growing corpus of research suggests that physical exercise can improve cognition, particularly executive functioning, in older adults. However, limitations of existing research have included (a) insufficient attention to the recruitment of sedentary older adults (who would most likely benefit from exercise interventions); (b) insufficient guidance in test selection drawing on neuropsychological theory and practice; and (c) failure to elucidate the multiple pathways or components of exercise effects on cognition. The current study sought to better clarify these routes to cognitive improvement via (a) assessment of both potential physical fitness and psychosocial mediators of exercise effects on cognition, and (b) inclusion of a control group that received a comparable psychoeducational intervention, matched in study contact hours and study-related non-exercise activities, but which did not receive a physical exercise enhancement intervention. Two randomized groups of 35 (control) and 34 (invention) adults aged 50 years and older were recruited from the Gainesville/Alachua County, Florida region. Both groups underwent pre- and post-intervention cognitive, fitness, and psychosocial/socioemotional assessment. The exercise promotion intervention group received 16 weeks of intervention (health and fitness education, weekly peer motivational coaching and group support, etc.) in small groups with a peer mentor, while a control/comparison group received 16 weeks of "health hygiene" instruction, consisting of 16 weeks of education about general health conditions in aging (also in small groups with a peer mentor). Repeated-measures MANOVA indicated no significant between-subjects effect of the intervention (p >.05). There were multivariate within-subjects effects for occasion; however, there were no study group-by-occasion interaction effects. Follow-up univariate analyses revealed within-subjects effects for 9 cognitive variables. There was a modest study group-by-occasion interaction on the COWA test, with intervention group participants improving significantly more across testing occasions. Next, exploratory age group analyses revealed significant multivariate between-subjects effects of age on executive measures only. Follow-up univariate analyses demonstrated age group effects for 4 cognitive variables. For each cognitive measure, younger participants performed significantly better than their older counterparts. In addition, there were study group-by-occasion interaction effects that suggested younger control participants performed better on the One-Back Mean RT SD task, while older intervention group participants performed significantly better on LM Delayed Recall. A three-way interaction suggested that younger intervention group participants improved significantly more over time than younger controls and older participants on the Trails B test. Finally, there was modest, but inconsistent, evidence for correlated change between cognitive, physical fitness/activity, and psychosocial variables. These findings lend some support to the previous literature suggesting the benefits of physical fitness/exercise improvements on cognitive function and the frontal aging hypothesis (West, 1996; Zimmerman et al., 2006). Future research should explore the benefits of physical and cognitive interventions in diverse samples of middle-aged and older individuals. Future studies should also explore the use of alternate cognitive and physical fitness assessment tools in elucidating the cognition-fitness relationship.