IntroductionEvidence from experimental RCTs of regular exercise programs in previously sedentary adults (Erickson et al. 2010) and cross-sectional studies of cardiorespiratory fitness (Barnes et al. 2003) have led to the view that engagement in regular aerobic exercise may both improve cognitive performance and even protect against cognitive decline (Lytle et al. 2004). In a RCT designed to examine the effects of a 12-week aerobic exercise program on brain structure and cognitive health we aimed to investigate (1) Does aerobic fitness correlate with cognitive performance at baseline? (2) Do cognitive measures increase after an exercise intervention?MethodsFifty-one sedentary adults (33 female, age 66 ±5.5 years) were randomly assigned to an exercise or waitlist group. The exercise group underwent supervised aerobic exercise sessions three times per week for 12-weeks. The waitlist group underwent the same exercise sessions following a 12 week delayed start. Participants underwent tests of cardiovascular fitness (VO2max) and a battery of neuropsychological tests at three time points; baseline, after 12 weeks and 24 weeks. The VO2max test was a continuous, incremental test on a cycle ergometer. The neuropsychological tests included tests that spanned the three main cognitive domains; executive function (EF), processing speed (PS) and memory (MEM), with the full battery described in the Whitehall II Imaging Study (Filippini et al. 2014). Raw neuropsychological data were normalized into z-scores and composite scores for each cognitive domain created by summing individual tests by category. Correlations between variables were conducted with partial correlation controlling for age, gender and qualification level. Change in each cognitive domain was assessed using repeated measures ANOVA.ResultsForty-one participants completed the intervention. Both groups increased VO2max after the exercise intervention (F(1,39) = 22.65, P < .001). There were no significant correlations between baseline VO2max and cognitive domain scores; there was however a trend for a positive association between VO2max and PS (r = .270, P = .063). When comparing change in each domain across time, there was a main effect of time for EF (F(2,36) = 23.81, P < .001) and MEM (F(2,26) = 8.16, P = .001), pairwise comparison identified an increase in EF and MEM between baseline and weeks 12 and 24. There was no main effect of group.ConclusionsWe observed a trend for a positive correlation between VO2max and PS at baseline.Whilst we observed an increase in both EF and MEM performance between baseline and weeks 12 and 24 in both groups, there was no difference between groups. These results highlight that the relationship between aerobic fitness and cognitive performance remains equivocal and further research exploring the specific mechanisms and proposed exercise ‘dose’ for cognitive health is warranted.