Associations of objectively measured built-environment attributes with youth moderate-vigorous physical activity: a systematic review and meta-analysis.

BACKGROUND: Understanding attributes of the built environment that influence children's and adolescents' habitual physical activity can inform urban design.
OBJECTIVE: To conduct a systematic review and meta-analysis of studies linking aspects of the built environment with youth moderate-vigorous activity, including walking. DATA SOURCES: The PubMed, Embase, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases were searched using relevant key words for articles published between January 2000 and March 2013. STUDY SELECTION: The included articles reported associations between children's or adolescents' objectively measured physical activity and residential neighbourhoods or activity settings defined with geographical information systems (GIS), street audits or global positioning systems (GPS). Excluded articles did not delineate neighbourhoods by residential address or were not written in English. Of 320 potentially relevant articles, 31 met the inclusion criteria, but only 23 (with a total of 6,175 participants, aged 8-17 years) provided sufficient data to derive effects (associations) of built-environment features on child or adolescent habitual moderate-vigorous activity. STUDY APPRAISAL AND SYNTHESIS
METHODS: Ten criteria were used to appraise the inclusion of studies. The effects were analysed as the difference in mean minutes of daily moderate-vigorous activity either between two levels of a dichotomous variable (e.g., neighbourhood park available or not within 800 m) or between predicted means corresponding to a difference of two standard deviations of a simple linear numeric variable (e.g., housing density per square kilometre). The magnitude of the difference in means was evaluated via standardization. The meta-analysis was performed with the 14 studies using GIS or street audits to relate a total of 58 specific built-environment features to daily activity. Each feature was categorized with two dichotomous variables to indicate whether the feature promoted playing and/or walking, and these variables were included in the meta-analytic model as moderators interacting with age and proportion of males in the study as linear numeric covariates.
RESULTS: The meta-analysed effects of built-environment features that encourage play (including sports and fitness) and/or walking on youth moderate-vigorous activity ranged between trivial and small. There was a moderate effect of age (15 versus 9 years) whereby play facilities, parks, playgrounds and features that facilitate walking had negative effects on children's activity but positive effects on adolescents' activity. In studies that located youth physical activity with GPS, walking to school produced small increases in activity compared with transport by car or bus, greater proportions of activity took place in streets and urban venues (40-80%) than in green spaces (20-50%), and more than half of children's outdoor activity occurred with a parent nearby. LIMITATIONS: The meta-analysis cannot quantify the additive effect when several built-environment features are provided in a given neighbourhood.
CONCLUSIONS: Children do not benefit to the same extent as adolescents from built-environment features that encourage walking and those designed or used for neighbourhood play.