Association of objectively measured physical activity with body components in European adolescents

Background

Physical activity (PA) is suggested to contribute to fat loss not only through increasing energy expenditure “per se” but also increasing muscle mass; therefore, it would be interesting to better understand the specific associations of PA with the different body’s components such as fat mass and muscle mass. The aim of the present study was to examine the association between objectively measured PA and indices of fat mass and muscle components independently of each other giving, at the same time, gender-specific information in a wide cohort of European adolescents.

Methods

A cross-sectional study in a school setting was conducted in 2200 (1016 males) adolescents (14.7 ±1.2 years). Weight, height, skinfold thickness, bioimpedance and PA (accelerometry) were measured. Indices of fat mass (body mass index, % fat mass, sum of skinfolds) and muscular component (assessed as fat-free mass) were calculated. Multiple regression analyses were performed adjusting for several confounders including fat-free mass and fat mass when possible.

Results

Vigorous PA was positively associated with height (p < 0.05) in males, whilst, vigorous PA, moderate-vigorous PA and average PA were negatively associated with all the indices of fat mass (all p < 0.01) in both genders, except for average PA in relation with body mass index in females. Regarding muscular components, vigorous PA showed positive associations with fat-free mass and muscle mass (all p < 0.05) in both genders. Average PA was positively associated with fat-free mass (both p < 0.05) in males and females.

Conclusion

The present study suggests that PA, especially vigorous PA, is negatively associated with indices of fat mass and positively associated with markers of muscle mass, after adjusting for several confounders (including indices of fat mass and muscle mass when possible). Future studies should focus not only on the classical relationship between PA and fat mass, but also on PA and muscular components, analyzing the independent role of both with the different PA intensities.

Uncoupling protein-2 gene polymorphisms are associated with obesity in Hungarian children

AIM

To determine the frequency of common polymorphisms of genes associated with energy metabolism among normal weight and overweight/obese children to look for effects on childhood obesity.

METHODS

Among 709 overweight/obese and 637 normal weight children (age 6-17 years), anthropometric measurements were carried out and genotyping for the following gene polymorphisms: β3 -adrenoreceptor Trp64Arg, uncoupling protein (UCP) -1 -3826 A/G, UCP-2 -866 G/A and exon 8 del/ins, UCP-3 -55 C/T and peroxisome proliferator-activated receptor-γ Pro12Ala.

RESULTS

On multivariate regression analysis adjusted for age and gender heterozygosity and homozygosity for the UCP-2 -866 A variant was associated with an odds ratio (OR) for obesity of 0.69 (95% CI: 0.52-0.92; p = 0.013) and 0.50 (95% CI: 0.32-0.79; p = 0.003), respectively, compared with G/G homozygotes. Heterozygotes and homozygotes for the UCP-2 exon 8 ins allele had an OR for obesity of 1.66 (95% CI: 1.24-2.23; p = 0.001) and 2.12 (95% CI: 1.23-3.63; p = 0.006), respectively, compared with del/del homozygotes. There were no significant differences in obesity risk in association with the other examined gene polymorphisms.

CONCLUSION

Common polymorphisms of the UCP-2 gene might influence the propensity to overweight/obesity in Hungarian children.

Independent and combined effects of physical activity and sedentary behavior on blood pressure in adolescents: gender differences in two cross-sectional studies

Objectives

To examine the independent and combined association of physical activity (PA) and sedentary behavior (SB) on both systolic (SBP) and diastolic blood pressure (DBP) in adolescents from two observational studies.

Methods

Participants from two cross-sectional studies, one conducted in Europe (n = 3,308; HELENA study) and the other in Brazil (n = 991; BRACAH study), were selected by complex sampling. Systolic and diastolic blood pressure (outcomes), PA and SB, both independently and combined, and potential confounders were analyzed. Associations were examined by multilevel linear regression.

Results

Performing the recommended amount of PA (≥60 min/d) attenuated the effect of SB on DBP in BRACAH study girls and in boys from both studies. In contrast, PA did not attenuate the effects of SB on the SBP of girls in the HELENA study. The combination of less than recommended levels of PA with 2–4 h/d of sedentary behavior was found to be associated with increased SBP in boys from both studies.

Conclusions

Meeting current PA recommendations could mediate the association between SB and DBP in both sexes. In boys, the joint effect of low levels of PA and excessive sedentary activity increases SBP levels. Longitudinal studies are required to confirm these findings.

Gestational weight gain and adiposity, fat distribution, metabolic profile, and blood pressure in offspring: the IDEFICS project

OBJECTIVE

To investigate the association between gestational weight gain (GWG) and total adiposity, body fat distribution, blood pressure (BP), and metabolic profile in offspring.

DESIGN

Cross-sectional study.

METHODS

Body mass index (BMI), waist, subscapular and tricipital skinfolds, and BP were measured and blood samples drawn in 12 775 children (aged 2-9 years) from the IDEFICS cohort. Overweight/obesity was defined by IOTF criteria. Parents filled in a questionnaire investigating child and familiar medical history and lifestyle. A section was dedicated to pregnancy history (including GWG).

RESULTS

Anthropometric indices linearly and significantly increased across GWG tertiles (BMI z-score: tertile I =0.08, 0.03-0.13; tertile II =0.16, 0.12-0.21; tertile III =0.34, 0.28-0.40, P<0.01, mean, 95% CI) by analysis of covariance (ANCOVA) adjusted by child sex, age and practice of sport, birth weight, current maternal BMI, parental education, gestational age, age at delivery, alcohol and smoking during pregnancy, maternal diabetes mellitus, gestational hypertension, and breastfeeding duration. After inclusion of BMI z-score among covariates, HbA1c significantly increased across tertiles (P=0.009) while no differences were observed for BP, serum insulin, HOMA index, blood glucose and lipids. The adjusted risk of overweight/obesity significantly increased by 14 and 22% in tertiles II and III respectively, in comparison with tertile I by logistic regression analysis controlling for covariates.

CONCLUSION

Maternal GWG is an independent predictor of total adiposity and body fat distribution in offspring during infancy. Exposure to perinatal factors should be taken into account for early prevention of overweight and obesity.

Physical activity attenuates the negative effect of low birth weight on leptin levels in European adolescents; the HELENA study

We examined whether physical activity (PA) influences the association between birth weight and serum leptin in adolescents. The study comprised a total of 538 adolescents (315 girls), aged 12.5-17.49 years, born at term (≥ 37 weeks of gestation). We measured serum leptin levels and time engaged in moderate-vigorous PA (MVPA) by accelerometry. There was an interaction effect between birth weight and meeting the PA recommendations (60 min/day MVPA) on leptin levels in girls (P = 0.023) but not in boys (P = 0.809). Birth weight was negatively associated with leptin levels in girls not meeting the PA recommendations (i.e. more than 60 min/day of MVPA) (β = -0.096, P = 0.009), whereas no significant association was observed in those meeting the PA recommendations (β = -0.061, P = 0.433). In conclusion, meeting the PA recommendations may attenuate the negative effect of low birth weight on serum leptin levels in European female adolescents.

Early inflammatory response in soft tissues induced by thin calcium phosphates

The inflammatory response to titanium and hydroxyapatite (HA)-coated titanium in living tissue is controlled by a number of humoral factors, of which monocyte chemoattractant protein-1 (MCP-1) has been specifically linked to the recruitment of monocytes. These cells subsequently mature into tissue-bound macrophages. Macrophages adhering to the proteins adsorbed at the implant surface play a pivotal role in initiating the rejection or integration of the foreign material. Despite this, little is known about the initial inflammatory events that occur in soft tissues following the implantation of titanium and HA-coated titanium implants. In this study, circular discs of commercially pure titanium (c.p. Ti) with either a thin crystalline HA coating or amorphous HA coating or uncoated were implanted subcutaneously into rats. The implants were retrieved after 24 and 72 h. The lactate dehydrogenase (LD) activity, DNA content, expression of MCP-1, interleukin-10 (IL-10), tumor necrosis factor α (TNF-α), as well as monocyte and polymorphonuclear granulocyte counts in the exudate surrounding the implants were analyzed. There were significantly higher DNA and LD levels around the titanium implants at 24 h compared with HA-coated titanium. A rapid decrease in MCP-1 levels was observed for all the implants over the period of observation. No statistically significant differences were found between the two HA-coated implants. Our results suggest a difference in the early soft-tissue response to HA-coated implants when compared with titanium implants, expressed as a downregulation of inflammatory cell recruitment. This suggests that thin HA coatings are promising surfaces for soft tissue applications.

Food consumption and screen-based sedentary behaviors in European adolescents: the HELENA study

OBJECTIVE

To examine the association between time spent on different sedentary behaviors and consumption of certain food and beverage groups in a sample of European adolescents.

DESIGN

Data from the Healthy Lifestyle in Europe by Nutrition in Adolescence Cross-sectional Study.

SETTING

Eight survey centers (Athens, Dortmund, Ghent, Lille, Rome, Stockholm, Vienna, and Zaragoza).

PARTICIPANTS

A total of 2202 participants (45.5% boys) aged 12½ to 17½ years.

MAIN OUTCOME MEASURES

Information on sedentary behaviors (weekdays and weekends) collected via a standardized self-reported questionnaire, including watching television, playing computer and video games, using the Internet for studying or recreation, and studying. Food and beverage consumption data of selected groups were obtained using 2 nonconsecutive 24-hour recalls.

RESULTS

Boys reporting more than 4 h/d of watching television, playing computer games, and using the Internet for recreation were more likely to consume sweetened beverages (weekends) (odds ratio [OR], 1.83 [95% CI, 1.21-2.75]; 1.99 [1.31-3.01]; and 1.73 [1.03-2.91], respectively), and less likely to consume fruit (weekdays) (0.39 [0.21-0.72], 0.37 [0.18-0.77], and 0.39 [0.19-0.78], respectively) than those who spent less than 2 h/d. Girls spending more time per day watching television and playing computer or video games (weekdays) and playing computer games or surfing the Internet for recreation (weekends) were more likely to drink sweetened beverages (OR, 1.89 [95% CI, 1.21-2.94]; 1.57 [1.00-2.46]; 2.14 [1.16-3.97]; and 2.30 [1.24-4.28], respectively) and less likely to consume fruit (weekdays) (0.43 [0.23-0.80], 0.40 [0.19-0.83], 0.37 [0.14-0.94], and 0.42 [0.20-0.85], respectively) than those who spent less than 2 h/d.

CONCLUSION

Increased television viewing and computer and Internet use during adolescence is associated with higher odds of consumption of sweetened beverages and lower odds of fruit consumption.

Impact of REV-ERB alpha gene polymorphisms on obesity phenotypes in adult and adolescent samples

BACKGROUND

REV-ERBα has been shown to regulate adipogenesis and lipid metabolism as well as to link the circadian timing system to whole body metabolic homeostasis. We thus tested whether polymorphisms in REV-ERBα could be associated with metabolic phenotypes in human population samples.

METHODS

We analyzed the associations between 5 REV-ERBα polymorphisms and anthropometric (body weight, body mass index (BMI), waist and hip circumferences), biochemical (plasma lipid, glucose and insulin levels) and clinical (systolic and diastolic blood pressure) variables in three population-based studies (MONICA Lille n=1155 adults, MONA LISA Lille n=1170 adults and HELENA n=1155 adolescents). We assessed in vitro, the potential influence of one REV-ERBα polymorphism in transient transfection assays using two different cell lines.

RESULTS

We observed significant and consistent associations between the T minor allele of the REV-ERBα rs2071427 polymorphism (located in intron 1) and higher BMI (mean allele effect=+0.33 kg m(-2)) in the MONICA Lille (P=0.02), MONA LISA (P=0.02) and HELENA (P=0.03) studies. The odds ratios for obesity associated with this allele were 1.67 (1.00-2.79) (P=0.05) in MONICA Lille, 1.29 (1.01-1.65) (P=0.04) in MONA LISA Lille and the odds ratio for overweight was 1.48 (1.08-2.03) (P=0.01) in HELENA. In transfection experiments in human hepatocyte-derived cell lines, the REV-ERBα intron 1 directed the transcription of a luciferase reporter gene independently of the rs2071427 polymorphism.

CONCLUSION

Our results suggest that the REV-ERBα rs2071427 polymorphism modulates body fat mass in both adult and young people.

Overweight in singletons compared to children with siblings: the IDEFICS study

The aim of this study was to compare the prevalence of overweight in only children to those with siblings and to explore potential behavioral mediating factors. This study relies upon cross-sectional data collected at survey centers in eight European countries participating in Identification and prevention of Dietary- and lifestyle-induced health EFfects In Children and infantS (IDEFICS). The present analysis is based on measured anthropometry and parent or guardian-reported socio-demographic characteristics. Subjects include 12 720 children aged 2-9 years for whom number of siblings was known. Singletons were more likely (odds ratio 1.52, 95% confidence interval (CI):1.34-1.72) to be overweight than their peers with siblings when controlling for factors related to childhood overweight, including survey country, parental education, parental weight, maternal age, child's age, birth weight and gender. The three southernmost countries have over threefold risk of overweight, dominated by Italy, compared with the north-central countries, which is not explained by the prevalence of singleton children. The excess risk of overweight among children without siblings was robustly observed even when considering behavioral mediating factors (playtime, screen time per day, dietary propensities for sugar or fat, parental attitudes towards food rewards and television in the child's bedroom). Among singletons aged 6-9 years, the excess risk of overweight was 1.70 (95% CI: 1.44-2.01) compared with 1.32 (95% CI: 1.10-1.60) in younger singletons.

Iron and vitamin status biomarkers and its association with physical fitness in adolescents: the HELENA study

There is a lack of studies that analyze the association between micronutrient-related biomarker status and physical fitness in adolescents. In the present study, biochemical parameters for iron and vitamin status were studied, along with objective measures of physical fitness in healthy male and female European adolescents. One thousand eighty-nine adolescents (580 girls, 12.5-17.5 yr) from the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) cross-sectional study were included. Hierarchical linear models were performed to determine the associations between micronutrient biomarkers and physical fitness. Age, seasonality, latitude, body mass index, menarche (in girls), and physical activity were used as covariates. For cardiorespiratory fitness, concentrations of hemoglobin, retinol, and vitamin C in male adolescents and β-carotene and 25(OH)D in female adolescents were associated with maximal oxygen consumption. For muscular fitness, concentrations of hemoglobin, β-carotene, retinol, and α-tocopherol in male adolescents and β-carotene and 25(OH)D in female adolescents were associated with better performance of the standing long jump test. In summary, concentrations of hemoglobin and most antioxidant vitamins in male adolescents and β-carotene and 25(OH)D in female adolescents were positively associated with cardiorespiratory and muscular fitness, after controlling for relevant confounders. The associations between physical fitness and iron or vitamin status observed in this cross-sectional study in adolescents should be followed up by a study specifically designed to evaluate causal relationships.

Main characteristics and participation rate of European adolescents included in the HELENA study

Background

Participation rate and response rate are key issues in a cross sectional large-scale epidemiological study. The objective of this paper is to describe the study population and to evaluate participation and response rate as well as the key nutritional status variables in male and female adolescents involved in the HELENA study.

Methods

A multi-stage random cluster sampling with a target sample of 3000 adolescents aged [12.5 to 17.5] years, stratified for geographical location and age, was carried out. Information for participants and non-participants (NP) was compared, and participation and response rates to specific questionnaires were discussed.

Results

3,865 adolescents aged [12.5 to 17.5] years (1,845 females) participated in the HELENA study, of whom 1,076 (568 females) participated in the blood sampling. 3,528 (1,845 females) adolescents were finally kept for statistical analysis. Participation rates for the schools and classes differed importantly between countries. The participation rate of pupils within the participating classes also differed importantly between countries. Sex ratio, mean age and BMI were similar between NP and participating adolescents within each centre, and in the overall sample. For all the questionnaires included in the database, the response rate of questionnaires was high (more than 80% of questions were completed).

Conclusion

From this study it could be concluded that participation rate differed importantly between countries, though no bias could be identified when comparing the key study variables between participants and non-participants. Response rate for questionnaires was very high. Future studies investigating lifestyle and health in adolescents can optimize their methods when considering the opportunities and barriers observed in the HELENA study.

Eating behaviour, insulin resistance and cluster of metabolic risk factors in European adolescents. The HELENA study

The present study examined the associations of food behaviours and preferences with markers of insulin resistance and clustered metabolic risk factors score after controlling for potential confounders, including body fat in European adolescents. A cross-sectional study "Healthy Lifestyle in Europe by Nutrition in Adolescence Cross-Sectional Study" of 3546 European adolescents aged 12.5-17.5 years was conducted, using a complete dataset on at least glucose, insulin and "Food Choice Questionnaire". Results indicated skipping breakfast, as well as the preference of some foods such as nuts, chocolate, burgers and pizzas, soft drinks or juices, explain part of homeostasis model assessment index variance. In addition, snacking regularly during school day is associated with higher metabolic risk score in females. In conclusion, the present findings suggest that intervention studies aimed to prevent insulin resistance and metabolic risk factors in youth should focus not only in influencing food and drink preferences, but also to ensure healthy food behaviour in adolescents. The harmful consequences in the choice of certain foods or drinks and food habits can be countered with proper planning and intervention programs to prevent insulin resistance and metabolic risk factors.

Muscular and cardiorespiratory fitness are independently associated with metabolic risk in adolescents: the HELENA study

OBJECTIVE

To examine the independent associations of muscular and cardiorespiratory fitness with clustered metabolic risk in adolescents.

METHODS

Participants were 709 adolescents (346 boys) from 10 European centers, aged 12.5-17.5 yr, evaluated as a part of the Healthy Lifestyle in Europe by Nutrition in Adolescents cross-sectional study (HELENA-CSS). A muscular fitness score was computed using handgrip strength and standing long jump. Cardiorespiratory fitness was measured using the 20-m shuttle run test. Age- and gender-specific z-scores of waist circumference, systolic blood pressure, triglycerides, ratio total cholesterol/high-density lipoprotein cholesterol, and insulin resistance (homeostasis model assessment) were summed to create a metabolic risk score.

RESULTS

Muscular fitness was negatively associated with clustered metabolic risk independent of cardiorespiratory fitness (β = -0.249, p < 0.001). Independent of muscular fitness, an inverse association was also found between cardiorespiratory fitness and clustered metabolic risk (β = 0.264, p < 0.001). The odds ratios for having a high clustered risk (above or equal 1 standard deviation) were 5.3 [95% confidence interval (CI) = 2.6-10.6] and 4.3 (95% CI = 2.0-9.3) in the least fit quartile compared with the most fit quartile for muscular and cardiorespiratory fitness, respectively. Significant differences in metabolic risk between muscular fitness levels persisted among non-overweight (p = 0.012) and overweight participants (p = 0.011).

CONCLUSION

Muscular and cardiorespiratory fitness are independently associated with metabolic risk in adolescents. These results support current physical activity recommendations for youth, which include muscle strengthening activities in addition to aerobic exercise.

The effect of ponderal index at birth on the relationships between common LEP and LEPR polymorphisms and adiposity in adolescents

This study examined the effect of ponderal index (PI) at birth on the relationships between eight common polymorphisms of the leptin (LEP) and leptin receptor (LEPR) genes and adiposity in adolescents. A total of 823 European adolescents (45.4% girls) aged 14.8 ± 1.4 years were genotyped for the LEP (rs2167270, rs12706832, rs10244329, rs2071045, and rs3828942) and LEPR (rs1137100, rs1137101, and rs8179183) polymorphisms. The PI was calculated from parental reports of birth weight and length. Fat mass index (FMI) was calculated. Analyses were adjusted for relevant confounders. An "adiposity-risk-allele score" based on genotypes at the three single-nucleotide polymorphisms (SNPs) associated with adolescents' FMI in adolescents within the lower tertile of PI was calculated. The LEP rs10244329 and rs3828942 polymorphisms were associated with higher FMI only in adolescents within the lower PI tertile (+0.55 kg/m(2) per minor T allele, P = 0.040, and +0.58 kg/m(2) per major G allele, P = 0.028, respectively). The LEPR rs8179183 polymorphism was significantly associated with higher FMI in adolescents within the lower PI tertile (+0.87 kg/m(2) per minor C allele, P = 0.006). After correction for multiple comparisons, only the association between the LEPR rs8179183 and FMI persisted. However, each additional risk allele conferred 0.53 kg/m(2) greater FMI in adolescents within the lower tertile of PI (P = 0.008). In conclusion, our results suggest that those adolescents born with lower PI could be more vulnerable to the influence of the LEP rs10244329 and rs3828942 polymorphisms and LEPR rs8179183 polymorphism on total adiposity content. Due to the relatively small sample size, these findings should be replicated in further larger population samples.

Physical activity attenuates the effect of low birth weight on insulin resistance in adolescents: findings from two observational studies

OBJECTIVE

To examine whether physical activity influences the association between birth weight and insulin resistance in adolescents.

RESEARCH DESIGN AND METHODS

The study comprised adolescents who participated in two cross-sectional studies: the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) study (n = 520, mean age = 14.6 years) and the Swedish part of the European Youth Heart Study (EYHS) (n = 269, mean age = 15.6 years). Participants had valid data on birth weight (parental recall), BMI, sexual maturation, maternal education, breastfeeding, physical activity (accelerometry, counts/minute), fasting glucose, and insulin. Insulin resistance was assessed by homeostasis model assessment-insulin resistance (HOMA-IR). Maternal education level and breastfeeding duration were reported by the mothers.

RESULTS

There was a significant interaction of physical activity in the association between birth weight and HOMA-IR (logarithmically transformed) in both the HELENA study and the EYHS (P = 0.05 and P = 0.03, respectively), after adjusting for sex, age, sexual maturation, BMI, maternal education level, and breastfeeding duration. Stratified analyses by physical activity levels (below/above median) showed a borderline inverse association between birth weight and HOMA-IR in the low-active group (standardized β = -0.094, P = 0.09, and standardized β = -0.156, P = 0.06, for HELENA and EYHS, respectively), whereas no evidence of association was found in the high-active group (standardized β = -0.031, P = 0.62, and standardized β = 0.053, P = 0.55, for HELENA and EYHS, respectively).

CONCLUSIONS

Higher levels of physical activity may attenuate the adverse effects of low birth weight on insulin sensitivity in adolescents. More observational data, from larger and more powerful studies, are required to test these findings.

Sleep duration and overweight in European children: is the association modified by geographic region?

STUDY OBJECTIVES

To investigate differences and a possible effect modification by geographical region in the association between sleep duration and overweight.

DESIGN

Cross-sectional.

SETTING

Primary schools and preschools in 8 European countries.

PARTICIPANTS

7867 children aged 2 to 9 years.

INTERVENTIONS

Not applicable.

MEASUREMENTS

Nocturnal sleep duration was assessed as part of a parental 24-h recall. Height and weight were measured by standardized procedures across centers. Data on personal, social, environmental and behavioral factors were collected using a standardized parental questionnaire.

RESULTS

Sleep duration differed (P < 0.001) between European regions and normal vs. overweight children. A dose-dependent inverse association between sleep duration and overweight could be seen, with crude odds ratios ranging from 1.73 (99% CI 1.33; 2.25) for sleeping between 10 and 11 h to 3.81 (99% CI 2.85; 5.09) for sleeping less than 9 h (reference category > 11 h). This persisted after adjustment, but remained significant only for sleeping less than 9 h per night (north: OR = 1.70; 99% CI 1.13; 2.58 vs. south: OR = 2.84; 99% CI 1.57; 5.12) if stratified by region. No effect modification by region could be found, but adjustment for region accounted for changes in the effect estimate for sleeping less than 9 h (OR = 2.22; 99% CI 1.64; 3.02). The association was stronger in school children than in preschool children.

CONCLUSION

Geographic region and related aspects-even if they do not seem to modify the association between sleep and overweight-should in any case be taken in consideration as a confounding factor on this association.

Comparison of several anthropometric indices with insulin resistance proxy measures among European adolescents: The Helena Study

The aim of the current study was to compare the association of several anthropometric indices, with insulin resistance (IR) proxy measures in European adolescents. The present study comprises 1,097 adolescents aged 12.5-17.5 from ten European cities participating in the HELENA study. Weight, height, waist circumference (WC) and hip circumference, skinfolds thickness, fat mass (FM), fasting plasma glucose (G(F)) and serum insulin (I(F)) levels were measured. HOMA (as indicator of IR body mass index (BMI), waist to hip ratio (WHR) and waist to height ratio (WHtR) were calculated. I(F) and HOMA were statistically significantly related to BMI, WC, skinfold sum, WHtR, WHR and FM. BMI, WC, WHtR, skinfold sum and FM displayed similar correlation with I(F) and HOMA as opposed to WHR where lower correlation with IR indices was detected in the overall sample. Similar results were found for boys, girls and underweight/normal weight adolescents. On the other hand, WC and WHtR were found to be more strongly associated with IR proxy measures compared to the rest of anthropometric indices among overweight/obese subjects. Based on the current findings, WC and WHtR could be used, alternatively, to identify the overweight/obese adolescent at risk for developing IR. In addition, all aforementioned anthropometric indices, except WHR, could be used among the underweight/normal weight adolescents.

Factors that influence weekday sleep duration in European children

STUDY OBJECTIVES

To compare nocturnal sleep duration in children from 8 European countries and identify its determinants.

DESIGN

Cross-sectional.

SETTING

Primary schools and preschools participating in the IDEFICS study.

PARTICIPANTS

8,542 children aged 2 to 9 years from 8 European countries with complete information on nocturnal sleep duration.

INTERVENTIONS

Not applicable.

MEASUREMENTS

Nocturnal sleep duration was assessed by means of a computer based parental 24-h recall. Data on personal, social, environmental, and behavioral factors were collected by means of standardized parental questionnaire. Physical activity was surveyed with accelerometers.

RESULTS

Nocturnal sleep duration in the participating countries ranged from 9.5 h (SD 0.8) in Estonia to 11.2 h (SD 0.7) in Belgium and differed significantly between countries (P < 0.001) in univariate as well as in multivariate analyses, with children from northern countries sleeping the longest. Sleep duration decreased by about 6 min with each year of age over all countries. No effect of season, daylight duration, overweight, parental education level, or lifestyle factors could be seen.

CONCLUSION

Sleep duration differs significantly between countries. Our findings allow for the conclusion that regional affiliation, including culture and environmental characteristics, seems to overlay individual determinants of sleep duration.