Intelligence Mediates Associations Between Sedentary Time, Moderate-to-vigorous Physical Activity, And Inhibitory Control In Young Adults

The associations between sedentary time (ST) and executive functions (EFs) are mixed, while habitual physical activity (PA) has been positively related to EFs in young adults. Higher general intelligence is a proxy for higher socioeconomic status (SES), a positive correlate of ST, PA, and EFs. Thus, intelligence may help explain the link between ST, PA, and EFs. PURPOSE: To assess the mediating effects of general intelligence on the relationships between ST and moderate-to-vigorous PA (MVPA) with inhibitory control (an aspect of EFs) in young adults. METHODS: A sub-sample of 554 young adults (360 females, Mage = 23.7 ± 0.61 years; BMI = 24.4 ± 4.2 kg·m-2) from the Avon Longitudinal Study of Parents and Children (ALSPAC) was analyzed. ST and MVPA (min·d-1) were measured with a hip-worn GT1M ActiGraph accelerometer over 7 days. ST and MVPA were defined using <100 and ≥ 2,020 counts per minute thresholds, respectively. Inhibitory control was measured using the Stop-Signal Task and expressed as the time required to stop an initiated motor response (stop signal reaction time [SSRT] = RT on Go trials - Stop Signal Delay; ms). General intelligence was measured with a vocabulary subtest from the Wechsler Intelligence Scale and expressed as correct responses to word cues. RESULTS: Mediation analyses adjusting for gender, relative grip strength, percent total body fat mass, MVPA (ST models), and ST (MVPA models) demonstrated that general intelligence mediated the association between higher ST and shorter SSRT (β = -0.03 ± 0.01, 95% bootstrap CI [CI for short]: -0.06, -0.01). ST was also directly related to shorter SSRT (β = −0.11, t(553) = -2.17, P = 0.03). General intelligence fully mediated a positive association between MVPA and shorter SSRT (β = -0.03 ± 0.01, 95% CI: -0.06, -0.01); the direct pathway (P = 0.67). CONCLUSION: Young adults who were more sedentary were less impulsive in their responses showing better inhibitory control, which was partly explained by higher general intelligence. Higher intelligence fully explained better inhibitory control in more physically active young adults. Since higher ST, MVPA and intelligence are associated with higher SES, future studies should explore how various aspects of SES may affect the link between sedentary behaviors, PA and higher-order cognition.