A network analysis involving mental difficulties, cognition, physical fitness, 24-hour movement components, fatness, and sociodemographic factors in children.

Background: Evidence supports the beneficial linear influence of diverse lifestyle behaviors on brain health since childhood; however, multiple behaviors -and not only one-simultaneously affect such outcomes. Therefore, the aim was to explore the multivariate relationship through a network analysis among mental difficulty and cognitive function with physical fitness (PF), 24-h movement components, fatness, and sociodemographic factors in children. Methods: Cross-sectional study involved 226 children (52.2 % boys) aged between six and 11 years. Mental difficulties were evaluated through the Strengths and Difficulties Questionnaire and cognitive function by the Raven's Colored Progressive Matrices Test. The body mass index and PF were assessed according to the procedures suggested by the Proesp-Br, while moderate-to vigorous-intensity physical activity (MVPA) using accelerometry. The socioeconomic level, sleep, and screen time were evaluated by questionnaires. A network analysis was carried out to evaluate the associations among variables and establish centrality measures. Results: Age and PF moderated the negative relationship between cognitive function and MVPA. Furthermore, the direct and inverse relationship between cognitive function and mental difficulties appears to be affected by the 24-h movement components. Finally, age, PF, and screen time are the nodes with higher values of expected influence, indicating more sensitivity to interventions for decreasing mental difficulty and improving cognitive function. Conclusion: Mental health and cognitive function were moderated by the multivariate interaction among age, PF, and the three 24-h movement components. Nonetheless, centrality measures from the network analysis suggest that PF, MVPA, and screen time are crucial nodes in order to implement future interventions.

Sedentary time play a moderator role in the relationship between physical fitness and brain-derived neurotrophic factor in children. A pilot study.

Aim: Despite some advances, there are many controversies concerning brain-derived neurotrophic factor (BDNF) and its relationships with variables related to physical fitness and sedentary time, especially in children. The aim of the study was to explore the moderating role of sedentary time on the association between physical fitness and BDNF. Therefore, this study will add to the perspective of understanding how much time children may spend being sedentary with no deleterious influence on the positive association between physical fitness and BDNF. Methods: This cross-sectional study included 44 children aged between 6 and 11 years (9.02 ± 1.43) from a public school in Porto Alegre, Brazil. Cardiorespiratory fitness (CRF) was determined by the 6-min walk/run test, and muscular strength was determined through the lower limb strength test (LLS). Sedentary time was assessed through accelerometers, and blood samples were collected to determine serum BDNF levels (z score). Moderation analysis was performed using the PROCESS macro adjusted for sex, age, somatic maturation, waist circumference, and socioeconomic level. Results: Sedentary time moderates the relationship between CRF and BDNF, such that children should spend less than 511 minutes per day sedentary to achieve the benefits of CRF in BDNF concentrations. Conclusion: Sedentary time plays a significant moderating role in the relationship between CRF and BDNF. Therefore, to promote brain health in children, both increasing physical fitness and reducing sedentary time might be encouraged.