Influence of neighbourhood safety on childhood obesity: a systematic review and meta-analysis of longitudinal studies.

Unsafe residential neighbourhoods are thought to be a risk factor for childhood obesity by discouraging physical activity while encouraging sedentary behaviours, but findings from cross-sectional studies are susceptible to selection bias (e.g. children who are obese disproportionately reside in unsafe neighbourhoods). A literature search was conducted in the Cochrane Library, PubMed, Web of Science and Google Scholar for articles published until January 2017 that used baseline neighbourhood safety levels to predict future weight-related behaviours and body-weight status among children aged 17 years and younger. Twenty-two prospective cohort studies conducted in seven countries were identified. The median sample size was 1,104, and the median follow-up was 3.5 years. Sixteen studies used parent-reported and/or child-reported neighbourhood safety measures, and six adopted some objective measures (e.g. county crime rate and interviewers' block observations). The meta-analysis found that living in unsafe neighbourhoods was associated with a reduction in children's physical activity by 0.13 h week-1 . Living in unsafe neighbourhoods predicted a trivial (but statistically significant) gain in body mass index but no change in childhood overweight/obesity risk. Current research indicates a limited influence of neighbourhood safety on childhood obesity; this finding could be partially due to measurement problems. Future longitudinal studies should adopt validated neighbourhood safety measures.