Associations of accelerometer measured school- and non-school based physical activity and sedentary time with body mass index: IPEN Adolescent study.

BACKGROUND: This study examined the strength, shape and direction of associations of accelerometer-assessed overall, school- and non-school-based moderate-to-vigorous physical activity (MVPA) and sedentary time (ST) with BMI among adolescents across the world. Second, we examined whether these associations differed by study site and sex. METHODS: Cross-sectional data from the IPEN Adolescent study, an observational multi-country study, were used. Participants wore an accelerometer for seven days, reported height and weight, and completed a socio-demographic survey. In total, 4852 adolescents (46.6% boys), aged 11-19 years (mean age = 14.6, SD = 1.7 years) were included in the analyses, using generalized additive mixed models. RESULTS: Adolescents accumulated on average 41.3 (SD = 22.6) min/day of MVPA and 531.8 (SD = 81.1) min/day of ST, and the prevalence of overweight and obesity was 17.2% (IOTF), but these mean values differed by country. Linear negative associations of accelerometer-based MVPA and ST with standardized BMI scores and the likelihood of being overweight/obese were found. School-based ST and non-school-based MVPA were more strongly negatively associated to the outcomes than non-school based ST and school-based MVPA. Study site moderated the associations; adolescent sex did not. No curvilinear associations were found. CONCLUSIONS: This multi-country study confirmed the importance of MVPA as a potential protective factor against overweight/obesity in adolescents. Non-school-based MVPA seemed to be the main driver of these associations. Unexpected results were found for ST, calling for further examination in methodologically sound international studies but using inclinometers or pressure sensors to provide more precise ST measures.

International Physical Activity and Built Environment Study of adolescents: IPEN Adolescent design, protocol and measures.

INTRODUCTION: Only international studies can provide the full variability of built environments and accurately estimate effect sizes of relations between contrasting environments and health-related outcomes. The aims of the International Physical Activity and Environment Study of Adolescents (IPEN Adolescent) are to estimate the strength, shape and generalisability of associations of the community environment (geographic information systems (GIS)-based and self-reported) with physical activity and sedentary behaviour (accelerometer-measured and self-reported) and weight status (normal/overweight/obese). METHODS AND ANALYSIS: The IPEN Adolescent observational, cross-sectional, multicountry study involves recruiting adolescent participants (ages 11-19 years) and one parent/guardian from neighbourhoods selected to ensure wide variations in walkability and socioeconomic status using common protocols and measures. Fifteen geographically, economically and culturally diverse countries, from six continents, participated: Australia, Bangladesh, Belgium, Brazil, Czech Republic, Denmark, Hong Kong SAR, India, Israel, Malaysia, New Zealand, Nigeria, Portugal, Spain and USA. Countries provided survey and accelerometer data (15 countries), GIS data (11), global positioning system data (10), and pedestrian environment audit data (8). A sample of n=6950 (52.6% female; mean age=14.5, SD=1.7) adolescents provided survey data, n=4852 had 4 or more 8+ hours valid days of accelerometer data, and n=5473 had GIS measures. Physical activity and sedentary behaviour were measured by waist-worn ActiGraph accelerometers and self-reports, and body mass index was used to categorise weight status. ETHICS AND DISSEMINATION: Ethical approval was received from each study site's Institutional Review Board for their in-country studies. Informed assent by adolescents and consent by parents was obtained for all participants. No personally identifiable information was transferred to the IPEN coordinating centre for pooled datasets. Results will be communicated through standard scientific channels and findings used to advance the science of environmental correlates of physical activity, sedentary behaviour and weight status, with the ultimate goal to stimulate and guide actions to create more activity-supportive environments internationally.

Development and validation of the neighborhood environment walkability scale for youth across six continents.

BACKGROUND: The IPEN International Physical Activity and Environment Network Adolescent project was conducted using common study protocols to document the strength, shape, and generalizability of associations of perceived neighborhood environment attributes with adolescents' physical activity and overweight/obesity using data from 15 countries. Countries did not use identical versions of the Neighborhood Environment Walkability Scale for Youth (NEWS-Y) to measure perceived neighborhood environment attributes. Therefore, this study derived a measurement model for NEWS-Y items common to all IPEN Adolescent countries and developed a scoring protocol for the IPEN Adolescent version of the NEWS-Y (NEWS-Y-IPEN) that maximizes between-country comparability of responses. Additionally, this study examined between- and within-country variability, and construct validity of the NEWS-Y-IPEN subscales in relation to neighborhood-level socio-economic status and walkability. METHODS: Adolescents and one of their parents (N = 5714 dyads) were recruited from neighborhoods varying in walkability and socio-economic status. To measure perceived neighborhood environment, 14 countries administered the NEWS-Y to parents and one country to adolescents. Confirmatory factor analysis was used to derive comparable country-specific measurement models of the NEWS-Y-IPEN. Country-specific standard deviations quantified within-country variability in the NEWS-Y-IPEN subscales, while linear mixed models determined the percentage of subscale variance due to between-country differences. To examine the construct validity of NEWS-Y-IPEN subscales, we estimated their associations with the categorical measures of area-level walkability and socio-economic status. RESULTS: Final country-specific measurement models of the factor-analyzable NEWS-Y-IPEN items provided acceptable levels of fit to the data and shared the same factorial structure with five latent factors (Accessibility and walking facilities; Traffic safety; Pedestrian infrastructure and safety; Safety from crime; and Aesthetics). All subscales showed sufficient levels of within-country variability. Residential density had the highest level of between-country variability. Associations between NEWS-Y-IPEN subscales and area-level walkability and socio-economic status provided strong evidence of construct validity. CONCLUSIONS: A robust measurement model and common scoring protocol of NEWS-Y for the IPEN Adolescent project (NEWS-Y-IPEN) were derived. The NEWS-Y-IPEN possesses good factorial and construct validity, and is able to capture between-country variability in perceived neighborhood environments. Future studies employing NEWS-Y-IPEN should use the proposed scoring protocol to facilitate cross-study comparisons and interpretation of findings.

Are children living on dead-end streets more active? Near-home street patterns and school-going children's time spent outdoors in Dhaka, Bangladesh.

This study aimed to investigate relationships between near-home street patterns and children's time spent outdoors (TSO). Participants were 60 (n=60) school-age Dhaka children, 7-11years old (16 girls and 44 boys) selected by a two-phase cluster sampling method. Data were collected from September 2010 to June 2011 by visiting each of 60 children's homes. Children's mean TSOs (in minutes) were reported by parents' face-to-face interviews, and near-home street pattern data were collected by systematic direct observations. The researchers also collected data on seven socio-demographic variables and three neighborhood built-environment variables. A backward selection based multiple linear regression was used to examine association between children's TSO and near-home street patterns. Results (adjusted R2=0.66 for weekdays and 0.68 for weekend) suggested that children's TSO were significantly associated with near-home street type: dead-end instead of through streets (28min on weekdays, p<0.01 and 66min on weekend, p<0.01). The width of the street, level of its branching and availability of an open space or playground near the house are also positively associated with TSO. Near-home street features significantly contribute to TSO in school-going children of Dhaka.