Longitudinal changes in device-measured physical activity from childhood to young adulthood: the PANCS follow-up study.

BACKGROUND: There is a lack of longitudinal studies examining changes in device-measured physical activity and sedentary time from childhood to young adulthood. We aimed to assess changes in device-measured physical activity and sedentary time from childhood, through adolescence, into young adulthood in a Norwegian sample of ostensibly healthy men and women. METHODS: A longitudinal cohort of 731 Norwegian boys and girls (49% girls) participated at age 9 years (2005-2006) and 15 years (2011-2012), and 258 of these participated again at age 24 years (2019-2021; including the COVID-19 pandemic period). Physical activity and sedentary time were measured using ActiGraph accelerometers. Linear mixed models were used to analyse changes in physical activity and sedentary time and whether low levels of childhood physical activity track, i.e., persist into young adulthood (nchange=721; ntracking=640). RESULTS: The most prominent change occurred between the ages of 9 to 15 years, with an increase in sedentary time (150 min/day) and less time spent in light (125 min/day), moderate (16 min/day), and vigorous physical activity (8 min/day). Only smaller changes were observed between the ages of 15 and 24 years. Changes in moderate-to-vigorous physical activity from childhood to young adulthood differed between subgroups of sex, tertiles of body mass index at baseline and tertiles of peak oxygen uptake at baseline. While the tracking models indicated low absolute stability of physical activity from childhood to young adulthood, children in the lowest quartiles of moderate-to-vigorous (OR:1.88; 95%CI: 1.23, 2.86) and total physical activity (OR: 1.87; 95%CI: 1.21, 2.87) at age 9 years were almost 90% more likely to be in these quartiles at age 24 years compared to those belonging to the upper three quartiles at baseline. CONCLUSIONS: We found a substantial reduction in physical activity and increase in time spent sedentary between age 9 and 15 years. Contrary to previous studies, using mainly self-reported physical activity, little change was observed between adolescence and young adulthood. The least active children were more likely to remain the least active adults and could be targeted for early intervention.

Effects of a school-based physical activity intervention on cardiometabolic health 5 years after cessation.

BACKGROUND: While there have been several school-based physical activity (PA) interventions targeting improvement in cardiovascular disease (CVD) risk factors, few have assessed long-term effects. The aim of this paper was therefore to determine intervention effects on CVD risk factors 5 years after cessation. METHODS: Two schools were assigned to intervention (n = 125) or control (n = 134). The intervention school offered 210 min/week more PA than the control school over two consecutive years (fourth and fifth grades). Follow-up assessment was conducted 5-year post-intervention (10th grade) where 180-210 (73%-85%) children provided valid data. Outcomes were CVD risk factors: triglyceride, total-to-high-density-lipoprotein-cholesterol ratio (TC:HDL ratio), insulin resistance, blood pressure (BP), waist circumference, and cardiorespiratory fitness (VO2peak ). Variables were analyzed individually and as a composite score through linear mixed models, including random intercepts for children. RESULTS: Analyses revealed significant sustained 5-year intervention effects for HDL (effect sizes [ES] = 0.22), diastolic BP (ES = 0.48), VO2peak (ES = 0.29), and composite risk score (ES = 0.38). These effects were similar to the immediate results following the intervention. In contrast, while TC:HDL ratio initially decreased post-intervention (ES = 0.27), this decrease was not maintained at 5-year follow-up (ES = 0.09), whereas WC was initially unchanged post-intervention (ES = 0.02), but decreased at 5-year follow-up (ES = 0.44). CONCLUSION: The significant effects of a 2-year school-based PA intervention remained for CVD risk factors 5 years after cessation of the intervention. As cardiometabolic health can be maintained long-term after school-based PA, this paper demonstrates the sustainability and potential of schools in the primary prevention of future CVD risk in children.

Secular and longitudinal physical activity changes in population-based samples of children and adolescents.

The aims of this study were to investigate whether physical activity (PA) and sedentary time (ST) in 9- and 15-year-olds differed between 2005-2006 and 2011-2012 (secular change), and to investigate changes in PA and ST from age 9 to 15 (longitudinal change). In 2005-2006, we invited nationally representative samples of Norwegian 9- (n=1470) and 15-year-olds (n=1348) to participate. In 2011-2012, we invited a new nationally representative sample of 9-year-olds (n=1945), whereas 15-year-olds (n=1759) were invited to participate either based on previous participation in 2005-2006 or from a random sample of schools. We assessed PA and ST objectively using accelerometers. In 2011-2012, both 9- and 15-year-olds spent more time sedentary (≥35.7 min/d, P<.001) and less time in light PA (≥35.2 min/d, P<.001) compared to their peers in 2005-2006. Nine-year-old girls also spent less time in moderate-to-vigorous PA (MVPA) (4.2 min/d, P=.041). In both age groups, the proportion accumulating an average of 60 min/d of MVPA did not differ between the two cohorts. From age 9 to 15, girls and boys decreased their time spent in LPA (≥106.7 min/d, P<.001) and in MVPA (≥20.8 min/d, P<.001). During the same period, ST increased by a mean of >2 h/d (P<.011). We observed an adverse secular change in PA from 2005-2006 to 2011-2012 among 9- and 15-year-olds, and a large decline in PA in the participants followed longitudinally from age 9 to 15 years.

The Andersen aerobic fitness test: New peak oxygen consumption prediction equations in 10 and 16-year olds.

Measurement of aerobic fitness by determining peak oxygen consumption (VO2peak ) is often not feasible in children and adolescents, thus field tests such as the Andersen test are required in many settings, for example in most school-based studies. This study provides cross-validated prediction equations for VO2peak based on the Andersen test in 10 and 16-year-old children. We included 235 children (n = 113 10-year olds and 122 16-year olds) who performed the Andersen test and a progressive treadmill test to exhaustion to determine VO2peak . Joint and sex-specific prediction equations were derived and tested in 20 random samples. Performance in terms of systematic (bias) and random error (limits of agreement) was evaluated by means of Bland-Altman plots. Bias varied from -4.28 to 5.25 mL/kg/min across testing datasets, sex, and the 2 age groups. Sex-specific equations (mean bias -0.42 to 0.16 mL/kg/min) performed somewhat better than joint equations (-1.07 to 0.84 mL/kg/min). Limits of agreement were substantial across all datasets, sex, and both age groups, but were slightly lower in 16-year olds (5.84-13.29 mL/kg/min) compared to 10-year olds (9.60-15.15 mL/kg/min). We suggest the presented equations can be used to predict VO2peak from the Andersen test performance in children and adolescents on a group level. Although the Andersen test appears to be a good measure of aerobic fitness, researchers should interpret cross-sectional individual-level predictions of VO2peak with caution due to large random measurement errors.

The effect of a two-year school-based daily physical activity intervention on a clustered CVD risk factor score-The Sogndal school-intervention study.

To evaluate changes in clustered cardiovascular disease (CVD) risk factors in 9-year-old children following a 2-year school-based physical activity intervention. In total, 259 children (age 9.3 ± 0.3 years) were invited, of whom 256 participated. The intervention group (63 boys, 62 girls) carried out 60-minute teacher-controlled daily physical activity over two school years. The control group (62 boys, 69 girls) had the curriculum-defined amount of physical education (45 minutes twice each week). Of these, 67% (171 total, 91 intervention) successfully completed both baseline and post-intervention of six CVD risk factors: systolic blood pressure (SBP), triglyceride (TG), total cholesterol-to-high-density lipoprotein cholesterol ratio (TC:HDL ratio), waist circumference (WC), the homeostasis model assessment for insulin resistance (HOMA), and peak oxygen uptake (VO2peak ). All variables were standardized by sex prior to constructing a cluster score (sum of z scores for all variables). The effect of the intervention on the cluster score was analyzed using linear multiple regression. The cluster score improved after the intervention (ES = .29). Furthermore, the analyses showed significant effects in favor of the intervention group for systolic blood pressure (ES = .35), total cholesterol-to-HDL-c ratio (ES = .23), triglyceride (ES = .40), and VO2peak (ES = .57). A teacher-led school-based physical activity intervention that is sufficiently long and includes a substantial amount of daily physical activity can beneficially modify children's clustered CVD risk profile.

Gender-specific effects of physical activity on children's academic performance: The Active Smarter Kids cluster randomized controlled trial.

Active learning combines academic content with physical activity (PA) to increase child PA and academic performance, but the impact of active learning is mixed. It may be that this is a moderated relationship in which active learning is beneficial for only some children. This paper examine the impact of baseline academic performance and gender as moderators for the effects of active learning on children's academic performance. In the ASK-study, 1129 fifth-graders from 57 Norwegian elementary schools were randomized by school to intervention or control in a physical activity intervention between November 2014 and June 2015. Academic performance in numeracy, reading, and English was measured and a composite score was calculated. Children were split into low, middle and high academic performing tertiles. 3-way-interactions for group (intervention, control)∗gender (boys, girls)∗academic performance (tertiles) were investigated using mixed model regression. There was a significant, 3-way-interaction (p=0.044). Both boys (ES=0.11) and girls (ES=0.18) in the low performing tertile had a similar beneficial trend. In contrast, middle (ES=0.03) and high performing boys (ES=0.09) responded with small beneficial trends, while middle (ES=-0.11) and high performing girls (ES=-0.06) responded with negative trends. ASK was associated with a significant increase in academic performance for low performing children. It is likely that active learning benefited children most in need of adapted education but it may have a null or negative effect for those girls who are already performing well in the sedentary classroom. Differences in gendered responses are discussed as a possible explanation for these results. TRIAL REGISTRATION: Clinicaltrials.gov registry, trial registration number: NCT02132494.

Validation of SenseWear Armband in children, adolescents, and adults.

SenseWear Armband (SW) is a multisensor monitor to assess physical activity and energy expenditure. Its prediction algorithms have been updated periodically. The aim was to validate SW in children, adolescents, and adults. The most recent SW algorithm 5.2 (SW5.2) and the previous version 2.2 (SW2.2) were evaluated for estimation of energy expenditure during semi-structured activities in 35 children, 31 adolescents, and 36 adults with indirect calorimetry as reference. Energy expenditure estimated from waist-worn ActiGraph GT3X+ data (AG) was used for comparison. Improvements in measurement errors were demonstrated with SW5.2 compared to SW2.2, especially in children and for biking. The overall mean absolute percent error with SW5.2 was 24% in children, 23% in adolescents, and 20% in adults. The error was larger for sitting and standing (23%-32%) and for basketball and biking (19%-35%), compared to walking and running (8%-20%). The overall mean absolute error with AG was 28% in children, 22% in adolescents, and 28% in adults. The absolute percent error for biking was 32%-74% with AG. In general, SW and AG underestimated energy expenditure. However, both methods demonstrated a proportional bias, with increasing underestimation for increasing energy expenditure level, in addition to the large individual error. SW provides measures of energy expenditure level with similar accuracy in children, adolescents, and adults with the improvements in the updated algorithms. Although SW captures biking better than AG, these methods share remaining measurements errors requiring further improvements for accurate measures of physical activity and energy expenditure in clinical and epidemiological research.

Does adiposity mediate the relationship between physical activity and biological risk factors in youth?: a cross-sectional study from the International Children's Accelerometry Database (ICAD).

BACKGROUND/OBJECTIVES: To model the association between accumulating 60 daily minutes of moderate-to-vigorous physical activity and a composite score of biological risk factors into a direct and an indirect effect, using abdominal obesity as the mediator. SUBJECTS/METHODS: Cross-sectional data from the International Children's Accelerometry Database (ICAD) including 6-18-year-old children and adolescents (N=3412) from 4 countries providing at least 3 days of accelerometry-assessed physical activity. A standardized composite risk score was calculated from systolic blood pressure and fasting blood samples of insulin, glucose, triacylglycerol and inverse HDL-cholesterol. Abdominal obesity was assessed by the waist-circumference:height ratio. Two-stage regression analysis, allowing for exposure-mediator interaction, was used for the effect decomposition. RESULTS: Participants achieving 60 daily minutes of moderate-to-vigorous physical activity had a 0.31 (95% CI: -0.39, -0.23) standard deviations lower composite risk score than those achieving less than 60 min. Modelling the associations suggested that 0.24 standard deviations (95% CI: -0.32, -0.16) was attributed to the direct effect and -0.07 (95% CI: -0.11, -0.02) to the indirect effect indicating that 22% of the total effect was mediated by central adiposity. Modelling 30 and 90 min of moderate-to-vigorous physical activity per day resulted in changes in the direct but not the indirect effect. CONCLUSIONS: One hour of daily moderate-to-vigorous physical activity was associated with clinically relevant differences in metabolic control compared to engagement in less than this minimally recommended amount. The majority of the difference was explained by the direct effect of physical activity.International Journal of Obesity advance online publication, 31 October 2017; doi:10.1038/ijo.2017.241.

Cross-sectional and prospective associations between physical activity, body mass index and waist circumference in children and adolescents.

OBJECTIVE: To study the cross-sectional and prospective associations between physical activity (PA) of different intensities, body mass index (BMI) and waist circumference (WC) in children and adolescents using isotemporal substitution modelling. METHODS: Physical activity (accelerometry), BMI and WC were assessed in 6- (n = 970), 9- (n = 2,423) and 15-year-olds (n = 1,544) in 2005/2006 and 2011/2012. Participants aged 9 years in 2005/2006 were followed prospectively to 2011/12 (age 15). Associations between PA of different intensities (light, moderate and vigorous), BMI and WC were examined using isotemporal substitution models. RESULTS: Substituting 10 min per day of sedentary time with light PA was associated with higher WC (0.17 to 0.29 cm, p ≤ 0.003)) in all age groups. Substituting 10 min per day of sedentary time with moderate PA was associated with lower WC in 6- and 9-year-olds (-0.32 to -0.47 cm, p ≤ 0.013)). Substituting 10 min per day of sedentary time with vigorous PA was associated with lower WC in 9- and 15-year-olds (-1.08 to -1.79 cm, p ≤ 0.015)). Associations were similar with BMI as the outcome. In prospective analyses, substituting sedentary time with light, moderate or vigorous PA at age 9 was not associated with BMI or WC at age 15. CONCLUSION: Substituting sedentary time with moderate PA appears favourably associated with adiposity in children, whereas vigorous PA may be required in adolescents. Cross-sectional associations were not replicated in prospective analyses.

Motor competence and cardiorespiratory fitness have greater influence on body fatness than physical activity across time.

We investigated the longitudinal associations among physical activity (PA), motor competence (MC), cardiorespiratory fitness (VO2peak ), and body fatness across 7 years, and also analyzed the possible mediation effects of PA, MC, and VO2peak on the relationships with body fatness. This was a seven-year longitudinal study with three measuring points (mean ages [in years] and respective sample size: 6.75±0.37, n=696; 9.59±1.07, n=617; 13.35±0.34, n=513). PA (moderate-to-vigorous PA-MVPA and vigorous PA-VPA) was monitored using accelerometers. MC was assessed by the "Körperkoordinationstest für Kinder-KTK" test battery. VO2peak was evaluated using a continuous running protocol until exhaustion. Body fatness was determined by the sum of four skinfolds. Structural equation modeling was performed to evaluate the longitudinal associations among PA, MC, VO2peak, and body fatness and the potential mediation effects of PA, MC, and VO2peak . All coefficients presented were standardized (z-scores). MC and VO2peak directly influenced the development of body fatness, and VO2peak mediated the associations between MVPA, VPA, MC, and body fatness. MC also mediated the associations between MVPA, VPA, and body fatness. In addition, VO2peak had the largest total association with body fatness (ß=-0.431; P<.05), followed by MC (ß=-0.369; P<.05) and VPA (ß=-0.112; P<.05). As PA, MC, and VO2peak exhibited longitudinal association with body fatness, it seems logical that interventions should strive to promote the development of fitness and MC through developmentally appropriate physical activities, as the synergistic interactions of all three variables impacted body fatness.

Validity of noninvasive composite scores to assess cardiovascular risk in 10-year-old children.

Agreement between and classification accuracy of six different noninvasive composite scores and a cardiovascular disease (CVD) risk factor score were investigated in 911 (466 boys and 445 girls) 10-year-old Norwegian children. A CVD risk factor score (triglyceride, total cholesterol/HDL ratio, homeostasis model assessment of insulin resistance, systolic blood pressure (SBP), waist-to-height ratio (WHtR), and cardiorespiratory fitness) and six noninvasive risk scores (fitness+three different measurements of fatness (body mass index (BMI), WHtR, and skinfolds), with and without inclusion of SBP) were calculated (mean z-score by gender). Agreement was assessed using Bland-Altman plots. The ability of noninvasive scores to correctly classify children with clustered CVD risk was examined by receiver operating characteristic (ROC) analysis and Cohen's kappa coefficient (κ). For both sexes, the noninvasive scores without SBP showed excellent AUC values (AUC=0.93-0.94, 95% CI=0.88-0.98) and moderate kappa values (κ=0.49-0.64) and had limits of agreement of 0.0±0.78-0.89 (arbitrary unit). Inclusion of SBP increased AUC values (AUC=0.96-0.97, 95% CI=0.94-0.99), kappa values (κ=0.58-0.69), and reduced limits of agreement (0.0±0.68-0.76). Noninvasive scores that include fitness and fatness provide acceptable agreement and classification accuracy, allowing for widespread early identification of children that might be at risk for developing CVD later in life. SBP should be included in the noninvasive score to improve classification accuracy if possible.

The association between angiogenic markers and fetal sex: Implications for preeclampsia research.

OBJECTIVE: Current research suggests sexual dimorphism between the male and female fetoplacental units, but with unknown relevance for preeclampsia. We investigated the association between fetal sex and concentrations of the angiogenic markers soluble Fms-like kinase 1 (sFlt-1), placental growth factor (PlGF), and sFlt-1/PlGF ratio in first and second-third trimester in women with/without preeclampsia, and the impact of fetal sex on the prognostic value of angiogenic markers for preeclampsia. STUDY DESIGN: Observational study in a prospective, population-based cohort of 2110 singleton pregnancies with 150 preeclampsia cases. RESULTS: Higher sFlt-1 concentrations were observed for women carrying female fetuses in first trimester (all, 1107.65 vs. 992.27pg/ml; preeclampsia cases, 1118.79 vs. 934.49pg/ml, p<0.05) and in second-third trimester (all, 1130.03 vs. 1043.15pg/ml; preeclampsia, 1480.30 vs. 1152.86pg/ml, p<0.05), with similar findings for the sFlt-1/PlGF ratio concentrations in first (29.67 vs. 27.39 p<0.05) and second-third trimester (3.56 vs. 3.22, p<0.05). In first trimester, log transformed concentrations of PlGF, sFlt-1 and sFlt-1/PlGF (all participants) and sFlt-1 (preeclampsia cases) associated with fetal sex in adjusted analyses (p<0.05). In second-third trimester, only log(sFlt-1) associated with fetal sex (all, p=0.028; preeclampsia, p=0.067) In receiver operating curve analysis, prediction of early-onset preeclampsia by sFlt-1/PlGF tended to be superior in pregnancies with female vs. male fetuses (p=0.06). CONCLUSION: Sexual dimorphism was observed for concentrations of angiogenic markers. Female fetal sex was associated to higher sFlt-1 and sFlt-1/PlGF ratio concentrations in both healthy pregnancies and women developing preeclampsia. Fetal sex should be considered in research and clinical use of angiogenic markers.

Accelerometry-based monitoring of daily physical activity in children with juvenile idiopathic arthritis.

OBJECTIVES: Juvenile idiopathic arthritis (JIA) may cause functional impairment, reduced participation in physical activity (PA) and, over time, physical deconditioning. The aim of this study was to objectively monitor daily free-living PA in 10-16-year-old children with JIA using accelerometry with regard to disease activity and physical variables and to compare the data with those from healthy age- and gender-matched controls. METHOD: Patients underwent an evaluation of disease activity, functional ability, physical capacity, and pain. Accelerometer monitoring was assessed using the GT1M ActiGraph. Normative data from two major studies on PA in Danish schoolchildren were used for comparison. RESULTS: Data of accelerometry were available for 61 JIA patients and 2055 healthy controls. Of the JIA patients, 57% showed below-average values of maximal physical capacity (fitness level). JIA patients showed low disease activity and pain and were physically well functioning. Accelerometer counts were lower in JIA patients than in controls. Accelerometer measurements were negatively correlated with disease activity, erythrocyte sedimentation rate (ESR), and number of joints with swelling and/or limited range of motion (ROM). No correlation was found between PA and pain scores, functional ability, and hypermobility. Patients with involvement of ankles or hips demonstrated significantly lower levels of PA. CONCLUSIONS: Children with JIA are less physically active and have lower physical capacity and fitness than their age- and gender-matched healthy peers despite good disease control. The involvement of hips or ankles is associated with lower PA.

Longitudinal influence of musculo-skeletal injuries and extra physical education on physical fitness in schoolchildren.

The aims of this study were to investigate if (A) injuries and (B) increased physical education (PE) influenced the development of physical fitness in schoolchildren. Simultaneously, to investigate if a possible PE effect was modified by sport participation outside school hours. This was a longitudinal controlled school-based study. Six schools with 270 min of PE (extra PE) and four schools with 90 min of PE were followed up for 2.5 years. In total, 1054 children were included for analysis (normal PE = 443, extra PE = 611). Development in fitness was analyzed using composite z-scores from six fitness tests measured four times. Information of injury and sport was derived from weekly automated mobile phone text messages surveying the presence of musculo-skeletal pain and organized sport participation. Injury and extra PE both influenced the development of physical fitness. Injury decreased development of physical fitness with -1.01 composite z-score units (95% CI: -1.57; -0.45). Extra PE increased physical fitness development with 0.80 (95% CI: 0.49; 1.10) composite z-score units. The influence of injury was not dependent on extra PE. No modifying effect was found by mean weekly sport participation outside school hours. In conclusion, extra PE had a positive effect, whereas injuries had a negative effect on physical fitness development in schoolchildren.

Effects of extra school-based physical education on overall physical fitness development--the CHAMPS study DK.

First, this study aimed to investigate if four extra physical education (PE) lessons per week improved children's development in physical fitness. Second, to investigate if the extra PE lessons improved development in physical fitness for children with lower levels of fitness at baseline. This study was a longitudinal controlled school-based study. The study population consisted of 10 Danish public schools with children in preschool to fourth grade (cohorts 0-4) with 2.5-year follow-up. Six schools had extra PE and four schools had normal PE. In total 1247 children were included (normal PE = 536, extra PE = 711). Development in fitness was analyzed using a composite z-score from six fitness tests. Multilevel mixed-effects linear regression was used to examine the association between school type and development in fitness. Extra PE increased the total development of composite z-score units among children enrolled in cohort 4 and borderline in cohort 3 with 1.06 (95% confidence interval 0.48-1.65) and 0.52 z-score units (-0.06 to 1.09), respectively. Children in the lower 50 percentiles increased their development with 0.47 (0.08-0.85) z-score units. Extra PE in schools improved development in fitness for cohort 4 and borderline for cohort 3 among all children. Extra PE improved fitness development across all cohorts among children with low fitness levels.

Maternal obesity and offspring dietary patterns at 9 months of age.

BACKGROUND/OBJECTIVES: Differences in the quality of complementary feeding between infants of obese and nonobese mothers have not been examined sufficiently. The aim of this paper was to compare dietary patterns, foods, nutrients and energy intakes of 9-month-old Danish infants in a cohort comprising obese mothers (SKOT II, n=184; SKOT, Danish abbreviation of small children's diet and well-being) with a cohort consisting mainly of nonobese mothers (SKOT I, n=329). SUBJECTS/METHODS: Dietary intake was assessed by 7-day records, and dietary patterns were identified by principal component analysis. RESULTS: SKOT I was characterized by a lower maternal body mass index (BMI) and a higher social class than SKOT II in relation to parental education and occupation. Infants in SKOT II had lower scores on a Health-Conscious Food pattern reflected at the food group level, for example, with lower intake of the food groups Fruit and Vegetable but higher intake of WheatBreadNoWholegrain in SKOT II compared with SKOT I. Moreover, SKOT II had shorter durations of breastfeeding, earlier introductions of complementary feeding, higher energy intake from protein but lower energy intakes from monounsaturated fatty acids and polyunsaturated fatty acids at 9 months. SKOT II had higher weight-for-age and length-for-age z-scores, but no differences in BMI z-scores, as compared with SKOT I at 9 months. CONCLUSIONS: Infants of obese mothers from a lower social class seem to have a less healthy diet and higher weight and length z-scores at 9 months. Therefore, the promotion of healthy complementary feeding might be beneficial for the prevention of health implications, such as obesity, later in life for these infants.

Associations between bicycling and carotid arterial stiffness in adolescents: The European Youth Hearts Study.

The aim of the study was to investigate the associations between bicycling and carotid arterial stiffness, independent of objectively measured moderate-and-vigorous physical activity. This cross-sectional study included 375 adolescents (age 15.7 ± 0.4 years) from the Danish site of the European Youth Heart Study. Total frequency of bicycle usage was assessed by self-report, and carotid arterial stiffness was assessed using B-mode ultrasound. After adjusting for pubertal status, body height, and objectively measured physical activity and other personal lifestyle and demographic factors, boys using their bicycle every day of the week displayed a higher carotid arterial compliance {standard beta 0.47 [95% confidence interval (CI) 0.07-0.87]} and distension [standard beta 0.38 (95% CI -0.04 to 0.81)]. Boys using their bicycle every day of the week furthermore displayed a lower Young's elastic modulus [standard beta -0.48 (95% CI -0.91 to -0.06)]. Similar trends were observed when investigating the association between commuter bicycling and carotid arterial stiffness. These associations were not observed in girls. Our observations suggest that increasing bicycling in adolescence may be beneficial to carotid arterial health among boys.

Examining the causal association of fasting glucose with blood pressure in healthy children and adolescents: a Mendelian randomization study employing common genetic variants of fasting glucose.

The aim of the study was to determine whether genetically raised fasting glucose (FG) levels are associated with blood pressure (BP) in healthy children and adolescents. We used 11 common genetic variants of FG discovered in genome-wide association studies (GWAS), including the rs560887 single-nucleotide polymorphism (SNP) located in the G6PC2 locus found to be robustly associated with FG in children and adolescents, as an instrument to associate FG with resting BP in 1506 children and adolescents from the European Youth Heart Study (EYHS). Rs560887 was associated with increased FG levels corresponding to an increase of 0.08 mmol l(-1) (P=2.4 × 10(-8)). FG was associated with BP, independent of other important determinants of BP in conventional multivariable analysis (systolic BP z-score: 0.32 s.d. per increase in mmol l(-1) (95% confidence interval (CI) 0.20-0.44, P=1.9 × 10(-7)), diastolic BP z-score: 0.13 s.d. per increase in mmol l(-1) (95% CI 0.04-0.21, P=3.2 × 10(-3)). This association was not supported by the Mendelian randomization approach, neither from instrumenting FG from all 11 variants nor from the rs560887, where non-significant associations of glucose with BP were observed. The results of this study could not support a causal association between FG and BP in healthy children and adolescents; however, it is possible that rs560887 has pleiotropic effects on unknown factors with a BP lowering effect or that these results were due to a lack of statistical power.

Maternal 25-hydroxyvitamin D level and fetal bone growth assessed by ultrasound: a systematic review.

OBJECTIVES: To assess systematically the role of maternal vitamin D levels in fetal bone growth. METHODS: PubMed, EMBASE and Cochrane databases were searched using the search words [Vitamin D] in combination with [fetal, fetus, intrauterine, or prenatal AND growth, development, bone, femur, or humerus]; [crown-rump length]; or [ultrasonography, prenatal]. Criteria for inclusion in this systematic review were data on maternal serum 25-hydroxyvitamin D (25(OH)D) during pregnancy and measurement of fetal growth by ultrasound. RESULTS: We identified 750 publications initially, from which five observational studies were selected for inclusion in the final review. The parameters studied were humerus length (HL) and femur length (FL) and their Z-scores, femoral volume, femoral distal metaphyseal cross-sectional area (CSA), femoral proximal metaphyseal diameter (PMD), femoral mid-shaft diameter and crown-rump length. In one study, 25(OH)D was associated directly with FL; in another study 25(OH)D only correlated with FL and HL Z-scores when calcium intake was insufficient. Two studies found no association between 25(OH)D and FL, but detected a direct association with femoral PMD, and an inverse relation with femoral distal metaphyseal CSA, respectively. CONCLUSIONS: Observational studies investigating the role of maternal vitamin D levels in fetal bone growth are sparse. Their evidence suggests that low maternal 25(OH)D levels may affect fetal bone growth under certain circumstances, especially in cases of simultaneous low calcium intake. Further studies are necessary.

Prospective association of adiposity and cardiorespiratory fitness with cardiovascular risk factors in healthy children.

This study aimed to examine the prospective association of three different measures of adiposity and cardiorespiratory fitness (CRF) with 2-year change in cardiovascular disease (CVD) risk factors in children. Two-year longitudinal data in schoolchildren aged 7-11 years (n = 365-729) was used. Total body fat (TBF) from dual-energy x-ray absorptiometry, body mass index (BMI), waist circumference (WC), CRF, blood samples, and blood pressure were obtained in 2008 and 2010 in the Childhood Health, Activity, and Motor Performance School Study in Denmark (CHAMPS study-DK). Greater adiposity at baseline was associated with increased CVD risk factor levels at follow-up. The magnitudes of associations were similar regardless of adiposity measure [TBF%: ß 0.30, 95% confidence interval (CI): 0.21-0.39; BMI: ß 0.24, 95% CI: 0.14-0.33; WC: ß 0.20, 95% CI: 0.10-0.31], and no evidence of nonlinear relationships was observed. We found less strong associations of CRF with increase in CVD risk factor levels after adjusting for adiposity; however, increasing CRF was still favorably associated with decrease in CVD risk factor levels among boys. Results suggest that any effort to shift the population distribution of adiposity downward would be valuable for early CVD prevention. The association of CRF with CVD risk factors was largely explained by adiposity, particularly among girls.