Anne Kær Gejl

Associations of Physical Activity, Sports Participation and Active Commuting on Mathematic Performance and Inhibitory Control in Adolescents

Objectives To examine objectively measured physical activity level, organized sports participation and active commuting to school in relation to mathematic performance and inhibitory control in adolescents. Methods The design was cross-sectional. A convenient sample of 869 sixth and seventh grade students (12–14 years) was invited to participate in the study. A total of 568 students fulfilled the inclusion criteria and comprised the final sample for this study. Mathematic performance was assessed by a customized test and inhibitory control was assessed by a modified Eriksen flanker task. Physical activity was assessed with GT3X and GT3X+ accelerometers presented in sex-specific quartiles of mean counts per minute and mean minutes per day in moderate-to-vigorous physical activity. Active commuting and sports participation was self-reported. Mixed model regression was applied. Total physical activity level was stratified by bicycling status in order to bypass measurement error subject to the accelerometer. Results Non-cyclists in the 2nd quartile of counts per minute displayed a higher mathematic score, so did cyclists in the 2nd and 3rd quartile of moderate-to-vigorous physical activity relative to the least active quartile. Non-cyclists in the 3rd quartile of counts per minute had an improved reaction time and cyclists in the 2nd quartile of counts per minute and moderate-to-vigorous physical activity displayed an improved accuracy, whereas non-cyclists in the 2nd quartile of counts per minute showed an inferior accuracy relative to the least active quartile. Bicycling to school and organized sports participation were positively associated with mathematic performance. Conclusions Sports participation and bicycling were positively associated with mathematic performance. Results regarding objectively measured physical activity were mixed. Although, no linear nor dose-response relationship was observed there was no indication of a higher activity level impairing the scholastic or cognitive performance.

Cross-sectional associations of objectively measured physical activity with brain-derived neurotrophic factor in adolescents

OBJECTIVE The purpose of this study was to examine the associations between objectively measured physical activity and serum brain-derived neurotrophic factor (BDNF) in adolescents. METHODS Cross-sectional analyses were performed using data from 415 adolescents who participated in the 2015 follow-up of the Childhood Health Activity and Motor Performance School Study Denmark (the CHAMPS-study DK). Physical activity was objectively measured by accelerometry monitors. Serum BDNF levels were analyzed using the Enzyme-linked immunosorbent assay (ELISA). Anthropometrics and pubertal status were measured using standardized procedures. RESULTS With adjustment for age, pubertal status and body mass index, mean physical activity (counts per minute) was negatively associated with serum BDNF in boys (P=0.013). Similarly, moderate-to-vigorous physical activity (MVPA) was negatively associated with serum BDNF in boys (P=0.035). In girls, mean physical activity and MVPA were not associated with serum BDNF. Without adjustment for wear time, sedentary time was not associated with serum BDNF in either sex. CONCLUSION These findings indicate that higher physical activity is associated with lower serum BDNF in boys, but not in girls.

Influence of a 2- to 6-year physical education intervention on scholastic performance: The CHAMPS study-DK

The aim of this study was to investigate the influence of a school‐based intervention with a tripling of physical education (PE) lessons from two (90 minutes) to six lessons per week (270 minutes) on scholastic performance. This study is part of the CHAMPS study‐DK, a quasi‐experimental study that began in 2008. The intervention group consisted of six schools, and the control group consisted of four matched schools (mean age at baseline=8.4 years, kindergarten class fourth grade). Academic performance was extracted from the national test system from 2010 to 2014 (Math and Danish were measured at third and sixth, and second, fourth and sixth grades, respectively). Participants included 1888 students participating in at least one scholastic performance test. Linear mixed models were applied to test for differences between groups and adjusted for known confounders. No significant differences were observed between groups in the academic performance tests (control group reference); Danish second grade β=−1.34 (95% CI −9.90, 7.22), fourth grade β=0.22 (95% CI −6.12, 6.56), sixth grade β=1.03 (95% CI −5.02, 7.08), and all grades combined β=0.28 (95% CI −5.74, 6.31) and Math third grade β=−2.87 (95% CI −9.65, 3.90), sixth grade β=0.99 (95% CI −7.36, 9.34) and combined β=−1.20 (95% CI −8.10, 5.71). In conclusion, no significant differences were observed between intervention and control schools for scholastic performance. Importantly, there were no negative effects of additional PE on scholastic outcomes, despite more PE and longer school days for intervention children.

The association between serum brain-derived neurotrophic factor and a cluster of cardiovascular risk factors in adolescents: The CHAMPS-study DK

Background and objective Cardiovascular disease and type 2 diabetes pose a global health burden. Therefore, clarifying the pathology of these risk factors is essential. Previous studies have found positive and negative associations between one or more cardiovascular risk factors and brain-derived neurotrophic factor (BDNF) probably due to diverse methodological approaches when analysing peripheral BDNF levels. Moreover, only a few studies have been performed in youth populations. Consequently, the main objective of this study was to examine the association between serum BDNF and a composite z-score consisting of six cardiovascular risk factors. A secondary aim was to examine the associations between serum BDNF and each of the six risk factors. Methods Four hundred and forty-seven apparently healthy adolescents between 11–17 years of age participated in this cross-sectional study. Cardiorespiratory fitness (CRF), anthropometrics, pubertal status, blood pressure (BP), serum BDNF, high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), blood glucose and insulin were measured. Information about alcohol consumption and socio-economic status was collected via questionnaires. Associations were modelled using linear regression analysis. Results Serum BDNF was positively associated with the composite z-score in the total study sample (standardized beta coefficient (std.β) = 0.10, P = 0.037). In males, serum BDNF was positively associated with the composite z-score (Std. β = 0.14, P = 0.034) and HOMA-IR (Std. β = 0.19, P = 0.004), and negatively associated with CRF (Std. β = -0.15, P = 0.026). In females, BDNF was positively associated with TG (Std. β = 0.14, P = 0.030) and negatively associated with waist circumference (WC) (Std. β = -0.16, P = 0.012). Conclusion Serum BDNF was positively associated with a composite z-score of cardiovascular risk factors. This association seems to be mainly driven by the association between TG, HOMA-IR and serum BDNF, and particularly for males. Further longitudinal research is warranted to determine the temporal relationship between BDNF and cardiovascular risk factors.

Associations between waist circumference, metabolic risk and executive function in adolescents: A cross-sectional mediation analysis

The main objective of this study was to investigate the associations between waist circumference, metabolic risk factors, and executive function in adolescents. Methods: The study was cross-sectional and included 558 adolescents (mean age 14.2 years). Anthropometrics and systolic blood pressure (sysBP) were measured and fasting blood samples were analyzed for metabolic risk factors. A metabolic risk factor cluster score (MetS-cluster score) was computed from the sum of standardized sysBP, triglycerides (TG), inverse high-density lipid cholesterol (HDLc) and insulin resistance (homeostasis model assessment). Cognitive control was measured with a modified flanker task. Results: Regression analyses indicated that after controlling for demographic variables, HDLc exhibited a negative and TG a positive association with flanker reaction time (RT). Waist circumference did not demonstrate a statistically significant total association with the cognitive outcomes. In structural equation modeling, waist circumference displayed an indirect positive association with incongruent RT through a higher MetS-cluster score and through lower HDLc. The only statistically significant direct association between waist circumference and the cognitive outcomes was for incongruent RT in the model including HDLc as mediator. Conclusions: These findings are consonant with the previous literature reporting an adverse association between certain metabolic risk factors and cognitive control. Accordingly, these results suggest specificity between metabolic risk factors and cognitive control outcomes. Further, results of the present study, although cross-sectional, provide new evidence that specific metabolic risk factors may mediate an indirect association between adiposity and cognitive control in adolescents, even though a direct association between these variables was not observed. However, taking the cross-sectional study design into consideration, these results should be interpreted with caution and future longitudinal or experimental studies should verify the findings of this study.

Associations Between Aerobic Fitness and Cognitive Control in Adolescents

Previous research has found positive associations between cognitive control and aerobic fitness in preadolescents and adults; however, fewer studies have investigated these associations in adolescents. Adolescence is of particular interest due to continued maturation of the prefrontal cortex; an area that subserves cognitive control. This study investigated the associations of aerobic fitness and cognitive control in adolescents. An assessment of aerobic fitness (Andersen intermittent running test) and two tests of cognitive control were collected to investigate these associations. Participants completed a test of inhibitory control (flanker task) and a test of cognitive flexibility (switch task). Along with traditional measures of reaction time (RT) and accuracy, diffusion modeling was utilized to combine these measures to calculate latent variables (i.e., drift rate, boundary separation, and nondecision time). Associations between cognitive measures and fitness were assessed with linear regressions while controlling for potential confounding factors. Higher fitness was associated with shorter reaction time and higher accuracy in the flanker task, indicating better inhibitory control performance. In addition, greater aerobic fitness was associated with greater quality of information uptake in the flanker task, as indicated by drift rate. In the switch task, higher aerobic fitness was associated with greater accuracy and longer switch RT indicating a speed-accuracy tradeoff. Results from the switch task diffusion modeling supported this conclusion as indicated by greater fitness associated with greater boundary separation, or response conservativeness. Further, greater drift rate in the switch task was associated with greater fitness. These findings corroborate growing evidence indicating the importance of aerobic fitness for inhibitory control and cognitive flexibility. This study extends the literature by demonstrating these effects in a large sample of adolescents with a computational model of the mechanisms that underlie cognition.