Associations of screen time, physical activity and neuromuscular fitness with brain structure in adolescents

Objective To explore the associations of total screen time, smart device use, physical activity, and neuromuscular fitness with brain gray matter volumes in adolescence. Methods Brain gray matter volumes were assessed using magnetic resonance imaging in 44 healthy adolescents (25 females and 19 males) aged 16–19 years. Physical activity and sedentary behavior questionnaires were used to assess screen time, including smart device use, and physical activity, including organized sports in sports clubs. Neuromuscular fitness was assessed using a score combining results of a 50-m shuttle-run test and a standing long jump test. Results Screen time and smart device use were negatively associated with medial temporal lobe volumes but positively associated with supplementary motor cortex and dorsal lateral prefrontal cortex volumes. Screen time was also positively related to left cuneus volume. Total physical activity was positively associated with right inferior occipital gyrus volume, but the association did not remain statistically significant after correction for multiple testing. Neuromuscular fitness was positively associated with parietal lobe volumes but negatively associated with right hippocampus and left posterior cingulate gyrus volumes, but these associations were no longer statistically significant after correction for multiple testing. Conclusion Longer screen time was related to lower medial temporal lobe volumes and larger frontal lobe volumes, whereas higher physical activity and better neuromuscular fitness were associated with larger volumes in the parietal and occipital regions. These findings highlight the complex relationships of screen time and physical activity with brain gray matter volumes in adolescence.