BackgroundPhysical activity and sedentary behaviour in youth have been reported to vary by sex, age, weight status and country. However, supporting data are often self-reported and/or do not encompass a wide range of ages or geographical locations. This study aimed to describe objectively-measured physical activity and sedentary time patterns in youth.MethodsThe International Children’s Accelerometry Database (ICAD) consists of ActiGraph accelerometer data from 20 studies in ten countries, processed using common data reduction procedures. Analyses were conducted on 27,637 participants (2.8–18.4 years) who provided at least three days of valid accelerometer data. Linear regression was used to examine associations between age, sex, weight status, country and physical activity outcomes.ResultsBoys were less sedentary and more active than girls at all ages. After 5 years of age there was an average cross-sectional decrease of 4.2 % in total physical activity with each additional year of age, due mainly to lower levels of light-intensity physical activity and greater time spent sedentary. Physical activity did not differ by weight status in the youngest children, but from age seven onwards, overweight/obese participants were less active than their normal weight counterparts. Physical activity varied between samples from different countries, with a 15–20 % difference between the highest and lowest countries at age 9–10 and a 26–28 % difference at age 12–13.ConclusionsPhysical activity differed between samples from different countries, but the associations between demographic characteristics and physical activity were consistently observed. Further research is needed to explore environmental and sociocultural explanations for these differences.Electronic supplementary materialThe online version of this article (doi:10.1186/s12966-015-0274-5) contains supplementary material, which is available to authorized users.

Childhood and adolescence are important developmental phases which influence health and well-being across the life span. Social relationships are fundamental to child and adolescent development; yet studies have been limited to children’s relationships with other humans. This paper provides an evidence review for the potential associations between pet ownership and emotional; behavioural; cognitive; educational and social developmental outcomes. As the field is in the early stages; a broad set of inclusion criteria was applied. A systematic search of databases and grey literature sources found twenty-two studies meeting selection criteria. The review found evidence for an association between pet ownership and a wide range of emotional health benefits from childhood pet ownership; particularly for self-esteem and loneliness. The findings regarding childhood anxiety and depression were inconclusive. Studies also showed evidence of an association between pet ownership and educational and cognitive benefits; for example, in perspective-taking abilities and intellectual development. Evidence on behavioural development was unclear due to a lack of high quality research. Studies on pet ownership and social development provided evidence for an association with increased social competence; social networks; social interaction and social play behaviour. Overall, pet ownership and the significance of children’s bonds with companion animals have been underexplored; there is a shortage of high quality and longitudinal studies in all outcomes. Prospective studies that control for a wide range of confounders are required.

BackgroundPrevious studies have suggested an effect of high arsenic concentration on cognitive and neurobehavioral function in humans.ObjectiveOur goal was to identify demographic and nutritional factors that are associated with As exposure and the influence of this exposure on cognitive function in school-age children.MethodsWe recruited 602 children 6–8 years of age living within 3.5 km of a metallurgic smelter complex in the city of Torreón, Mexico, to participate in a cross-sectional evaluation. Of these, 591 had complete anthropometry, iron, and zinc status by biochemical measurements in serum, blood lead concentration (PbB), and arsenic in urine (UAs), and 557 completed several cognitive performance tests.ResultsThe mean for UAs was 58.1 ± 33.2 μg/L; 52% of the children had UAs concentrations > 50 μg/L, and 50.7% of children had PbB ≥10 μg/dL. UAs concentration was associated with low socioeconomic status. Nutritional status indicators were not related to UAs concentrations. Linear and logistic regressions adjusted for hemoglobin concentration, PbB, and sociodemographic confounders showed a significant inverse association between UAs and Visual–Spatial Abilities with Figure Design, the Peabody Picture Vocabulary Test, the WISC-RM Digit Span subscale, Visual Search, and Letter Sequencing Tests (p < 0.05). Boys excreted significantly more UAs (p < 0.05) and were affected on different cognitive areas than girls.ConclusionsChildren living in an area contaminated with both As and lead showed that As contamination can affect children’s cognitive development, independent of any effect of lead.

Around the world, many women continue to experience low levels of autonomy. Recent literature has reported that the health consequences of low maternal autonomy extend beyond mothers and translate into health consequences for their children, and may be an important causal factor in child malnutrition. This review summarises the current knowledge of the relationship between maternal autonomy and children's nutritional status (defined as any measure that reflects the nutritional state of the body, such as birthweight or anthropometric scores) and child-feeding practices. The review also includes both discussion of the limitations found in the literature and directions for future research. A systematic review of the literature was conducted. Results of the studies included in the review strongly suggest that raising maternal autonomy is an important goal for improving children's nutritional status, yet gaps in the current knowledge exist, further confounded by issues with how autonomy is measured and limitations of cross-cultural comparability. A thorough understanding of the consequences of restricting women's autonomy will inform programmes and policy worldwide, and speed progress towards both empowering women and alleviating the global burden of child malnutrition.

Physical activity declines during youth but most evidence reports on combined moderate and vigorous-intensity physical activity. We investigated how vigorous-intensity activity varies with age.Cross-sectional data from 24,025 participants (5.0–18.0 y; from 20 studies in 10 countries obtained 2008–2010) providing ≥ 1 day accelerometer data (International Children's Accelerometry Database (ICAD)). Linear regression was used to investigate age-related patterns in vigorous-intensity activity; models included age (exposure), adjustments for monitor wear-time and study. Moderate-intensity activity was examined for comparison. Interactions were used to investigate whether the age/vigorous-activity association differed by sex, weight status, ethnicity, maternal education and region.A 6.9% (95% CI 6.2, 7.5) relative reduction in mean vigorous-intensity activity with every year of age was observed; for moderate activity the relative reduction was 6.0% (5.6%, 6.4%). The age-related decrease in vigorous-intensity activity remained after adjustment for moderate activity. A larger age-related decrease in vigorous activity was observed for girls (− 10.7%) versus boys (− 2.9%), non-white (− 12.9% to − 9.4%) versus white individuals (− 6.1%), lowest maternal education (high school (− 2.0%)) versus college/university (ns) and for overweight/obese (− 6.1%) versus healthy-weight participants (− 8.1%). In addition to larger annual decreases in vigorous-intensity activity, overweight/obese individuals, girls and North Americans had comparatively lower average vigorous-intensity activity at 5.0–5.9 y.Age-related declines in vigorous-intensity activity during youth appear relatively greater than those of moderate activity. However, due to a higher baseline, absolute moderate-intensity activity decreases more than vigorous. Overweight/obese individuals, girls, and North Americans appear especially in need of vigorous-intensity activity promotion due to low levels at 5.0–5.9 y and larger negative annual differences.

Lead exposure is a legacy issue that continues to affect vulnerable population groups globally, but particularly in low and middle-income countries (LMICS). We take a multi-disciplinary approach to examine the patterns of lead exposure in these countries, discuss the underlying injustices and socio-political causes, and the economic costs that are associated with exposure. We conclude with some lessons we drew from our discussion of lead across the disciplines and advocate for a number of approaches to solving this ongoing issue. These include (i) biomonitoring that could be integrated into existing health surveys or public health programs targeting young children; (ii) greater civic engagement to push for solutions; and, (iii) environmental control policies that represent a continuum of local, context-specific to broad, national-level, and even global approaches.

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Lead exposure and nutritional factors are both associated with cognitive performance. Lead toxicity and nutritional status are also associated with each other. We examined whether nutritional status variables account for part or all of the association between cognitive performance and lead exposure. First-grade children (n = 724) ages 6-8 y, attending Mexican public schools located in the vicinity of a metal foundry were asked to participate and 602 enrolled in the study. Blood lead, iron status, anemia, anthropometry, and cognitive function were assessed. Results from 7 standardized tests are presented here. The mean blood lead concentration was 11.5 +/- 6.1 micro g/dL (0.56 +/- 0.30 micro mol/L) and 50% of the children had concentrations >10 micro g/dL (0.48 micro mol/L). The prevalence of mild anemia (<124 g/L) was low (10%) and stunting (<2 SD) was nonexistent (2.3%). In bivariate analyses, lead was negatively associated with 4 cognitive tests and was also inversely correlated with iron status, height-for-age Z scores, and head circumference. In multivariate models, the association between lead and cognitive performance was not strongly affected by nutritional variables, suggesting that the relation of lead to cognition is not explained by lead's relation to iron deficiency anemia or growth retardation. In multivariate models, hemoglobin concentration was also positively associated with Peabody Picture Vocabulary Test and Number Sequencing performance, whereas serum ferritin was negatively related to the Coding subscale of the Wechsler Intelligence Scales for Children-Revised Mexican Version (WISC-RM).