Associations of Physical Activity and Screen Time with White Matter Microstructure in Children from the General Population

Background: Physical activity and sedentary behaviors have been linked to a variety of general health benefits and problems. However, few studies have examined how physical activity during childhood is related to brain development, with the majority of work to date focusing on cardio-metabolic health. This study examines the association between physical activity and screen time with white matter microstructure in the general pediatric population. Methods: In a sample of 2,532 children (10.12 ± 0.58 years; 50.04% boys) from the Generation R Study, a population-based cohort in Rotterdam, the Netherlands, we assessed physical activity and screen time using parentreported questionnaires. Magnetic resonance imaging of white matter microstructure was conducted using diffusion tensor imaging. Findings: Total physical activity was positively associated with global factional anisotropy (β=0.057, 95% CI= 0.016, 0.098, p=0.007) and negatively associated with global mean diffusivity (β=-0.079, 95% CI= - 0.120, -0.038, p 0.05). Interpretation: This study provides new evidence that physical activity is modestly associated with white matter microstructure in children. In contrast, screen time was not associated with white matter microstructure. Causal inferences from these modest associations must be interpreted cautiously in the absence of longitudinal data. However, these data still offer a promising avenue for future work to explore to what extent physical activity may promote healthy white matter development. Funding Statement: The Sophia Foundation (S18-20 awarded to RM) and Netherlands Organization for Health Research and Development (ZonMw) (project 016.VICI.170.200, awarded to HT and TOP 91211021, awarded to TW). Declaration of Interests: The authors report no biomedical financial interests or potential conflicts of interest. Ethics Approval Statement: The Medical Ethics Committee of the Erasmus Medical Center approved the study procedures and participants provided written informed consent.