Assessment of physical activity intensity and duration in the paediatric population: evidence to support an a priori hypothesis and sample size in the agreement between subjective and objective methods.

We aimed to provide evidence for an a priori hypothesis and sample size for subjectively assessing physical activity intensity and duration in paediatric population, adopting objective methods as the reference. We searched electronic databases, reference lists and author databases. Correlation coefficients were pooled as an indicator of agreement estimates. We found 183 agreement analyses (94.5% based on correlation coefficients) from 89 studies that met our inclusion criteria. We identified four physical activity parameters addressing intensity and two parameters addressing duration. The physical activity parameters focusing on intensity were measured only by questionnaires, and the best correlation was achieved by moderate-to-vigorous physical activity compared with a heart rate monitor. In addition, total physical activity duration had a stronger correlation with an accelerometer when measured by diaries or logs than when measured by questionnaires. In both cases, the correlation was moderate. Studies with sample sizes between 50 and 99 subjects showed measurements that were stable in both magnitude and interpretation. Our findings suggest that the agreement between subjective and objective methods for assessing physical activity intensity and duration is weak to moderate. Furthermore, sample sizes ranging from 50 to 99 subjects provide stable agreement estimates between methods.

Abdominal obesity and its association with socioeconomic factors among adolescents from different living environments.

BACKGROUND: Socioeconomic status has been associated with obesity in children and adolescents. This association may be dependent according with where adolescents lives. OBJECTIVE: The aim of this study was to evaluate the association between different socioeconomic indicators such as parental education and occupation and socioeconomic status with abdominal obesity in adolescents from two observational studies: the Healthy Lifestyle in Europe by Nutrition in Adolescence cross-sectional study (HELENA-CSS) and the Brazilian Cardiovascular Adolescent Health (BRACAH) study. METHODS: European (n = 3192, aged 12.5-17.5 years, with 53.1% girls from HELENA-CSS) and Brazilian (n = 991, aged 14-18 years, with 54.5% girls from BRACAH study) adolescents from two cross-sectional studies were included in this analysis. Complete data on waist circumference (WC), height, socioeconomic status indicators and several confounders were collected. Socioeconomic indicators were measured using a self-reported questionnaire in order to assess the family social status of the adolescents. Multilevel linear regression models were used to examine associations, and results were adjusted for potential confounders. RESULTS: Adjusted results showed inverse associations between mother's and father's education levels (p < 0.001) and father's occupation level (p < 0.001) with waist-to-height ratio (WHtR) and WC in HELENA-CSS girls. Similarly in European girls, socioeconomic indicators by socioeconomic status and maternal occupation level were associated with WHtR. In HELENA-CSS boys, the same significant association was found between WHtR and WC with maternal occupation level. Moreover, in European boys WHtR was also associated with parental education. In Brazilian adolescents, both indicators of abdominal obesity did not remain associated with the independents variables, after adjustment for potential confounders. CONCLUSIONS: Abdominal obesity was associated with socioeconomic indicators in higher-income countries, but this association was not observed in a lower-middle-income country.

Inflammation profile in overweight/obese adolescents in Europe: an analysis in relation to iron status.

BACKGROUND/OBJECTIVES: The objectives of this study were to investigate the relationship between inflammatory parameters (CRP, c-reactive protein; AGP, α1-acid glycoprotein), iron status indicators (SF, serum ferritin; sTfR, soluble transferrin receptor) and body mass index (BMI) z-score, fat-free mass (FFM) and fat mass (FM) in European adolescents. Differences in intake for some nutrients (total iron, haem and non-haem iron, vitamin C, calcium, proteins) were assessed according to BMI categories, and the association of nutrient intakes with BMI z-score, FM and FFM was evaluated. METHODS: A total of 876 adolescents participating in the Healthy Lifestyle in Europe by Nutrition in Adolescence-Cross Sectional Study were included in the study sample. RESULTS: Mean CRP values (standard error; s.e.) were significantly higher in overweight/obese adolescents (1.7±0.3 and 1.4±0.3 mg/l in boys and girls, respectively) than in thin/normal-weight adolescents (1.1±0.2 and 1.0±0.1 mg/l in boys and girls, respectively) (P<0.05). For boys, mean SF values (s.e.) were significantly higher in overweight/obese adolescents (46.9±2.7 µg/l) than in thin/normal-weight adolescents (35.7±1.7 µg/l) (P<0.001), whereas median sTfR values did not differ among BMI categories for both boys and girls. Multilevel regression analyses showed that BMI z-score and FM were significantly related to CRP and AGP (P<0.05). Dietary variables did not differ significantly among BMI categories, except for the intake of vegetable proteins, which, for boys, was higher in thin/normal-weight adolescents than in overweight/obese adolescents (P<0.05). CONCLUSIONS: The adiposity of the European adolescents was sufficient to cause chronic inflammation but not sufficient to impair iron status and cause iron deficiency.

Prevalence of cardiovascular risk factors among Latin American adolescents: a multilevel analysis.

High blood pressure (HBP) and obesity is a well-established major risk factor for stroke and coronary heart disease. However, the literatures are scarce about these informations in adolescents from low-and-middle income countries. This school-based survey was carried out among students from Maringá (Brazil) and Buenos Aires (Argentina) selected random sampling. We studied 991 Brazilian adolescents (54.5% girls) in the age range of 14-18 years. In Argentina, we studied 933 adolescents (45.9% female) in the age range of 11-17 years. The outcomes of this study are general obesity, abdominal obesity and HBP. The associated factors analysed were gender, age and health behaviours. The prevalence of obesity was 5.8% in Brazil and 2.8% in Argentina, the prevalence of abdominal obesity was 32.7% in Brazil and 11.1% in Argentina, the prevalence of HBP was 14.9% in Brazil and 13.5% in Argentina. The multilevel analysis showed that older adolescents (>14 years old) have a little likelihood of being overweight, whereas male adolescents are more likely to be obese and have HBP. The abdominal obesity in both indicators were not associated with the independent variables. The prevalence of cardiovascular risk factors is high in Latin American adolescents independent of each country, and was associated with male gender.

Sleep time and cardiovascular risk factors in adolescents: the HELENA (Healthy Lifestyle in Europe by Nutrition in Adolescence) study.

OBJECTIVE: We aimed to examine the association between adolescents' sleep time and a cardiometabolic risk score. A second aim was to examine associations between sleep time and individual cardiometabolic risk factors. METHODS: Adolescents (N=699; ages, 12.5-17.5 years) participating in the HELENA (Healthy Lifestyle in Europe by Nutrition in Adolescence) study were examined. Sleep time was reported by a questionnaire. Physical activity (PA) was assessed by accelerometry (n=497). Cardiometabolic risk factors measurements included insulin resistance, blood pressure, adiposity markers, cardiorespiratory fitness, and blood lipids. A cardiovascular disease risk score was computed. Associations were examined by a multilevel regression analysis (linear for individual risk factors and Poisson for the clustered risk score). RESULTS: For school days no association was found between sleep time and cardiometabolic risk factors. At weekend days, the prevalence ratio (PR) of having a clustered risk score increased by 15% for each additional hour of sleep controlling for age, sex, and socioeconomic status (SES); however, the prevalence disappeared when adjusting for PA. CONCLUSIONS: In European adolescents sleep time is not associated with cardiometabolic risk factors when important confounders are considered. Future research about sleep cardiovascular risk factors should register other sleep dimensions (sleep patterns or disturbances) to provide a better insight in this scientific field.

Prevalence of abdominal obesity in adolescents: a systematic review.

The objectives of this study were to (i) review extant literature on the prevalence of abdominal obesity (AO) in adolescents of both sex (10-19 years old); (ii) analyse the cut-off points used for the diagnosis of AO and (iii) compare its prevalence between developed and developing countries. The search was carried out using online databases (MEDLINE, Web of Science, EMBASE, SPORTDiscus, SCIELO and BioMed Central), references cited by retrieved articles and by contact with the authors, considering articles published from the establishment of the databanks until 19 October 2009. Only original articles and those using waist circumference in the diagnosis were considered. Twenty-nine studies met the inclusion criteria. Fourteen of these studies were performed in developed countries. The prevalence of AO varied from 3.8% to 51.7% in adolescents from developing countries. The range of results was smaller among developed countries; with values from 8.7% to 33.2%. Eighteen different cut-off points were used. It was concluded the AO prevalence is high among adolescents, but is not clear what sex has a higher proportion and it is greater in adolescents from developing countries; however, there is no consensus in the literature about the criteria to be used.