Children's blood pressure and its association with road traffic noise exposure - A systematic review with meta-analysis.

BACKGROUND: Primary and synthetic research on road traffic noise (RTN) and blood pressure (BP) is more common for adults than it is for children and adolescents. Given the conflicting evidence from primary studies, this study aimed to conduct an up-to-date systematic review with meta-analysis of the association between RTN and children's BP, by using advanced statistical techniques, to take into account the heterogeneity in primary studies. METHODS: MEDLINE (PubMed), EMBASE (ScienceDirect with filters), and the Internet (Google) were searched (last update: July 21, 2016) in English, Spanish, and Russian. Thirteen articles (total n=8 770) were included in the systematic review and 37 effect size estimates were pooled in different meta-analyses under the quality effects model. RESULTS: Results showed 0.48mmHg (95% CI: -0.87, 1.83) increase in systolic blood pressure (SBP) and 0.22mmHg (95% CI: -0.64, 1.07) in diastolic blood pressure (DBP) per 5dB increase in RTN at school/kindergarten; and 0.20mmHg (95% CI: -0.30, 0.71) increase in SBP and 0.03mmHg (95% CI: -0.18, 0.25) in DBP per 5dB increase in RTN at home. There was high heterogeneity in the first three models and evidence of publication bias in the first. The following categorical and linear factors were significant effect modifiers in different exposure - outcome scenarios: country where the study was conducted, the mode of noise assessment, the mode of BP measurement, the type of reported effect size estimate, the overall quality score of the estimate, the minimum number of BP readings, and children's mean age. CONCLUSIONS: All evidence considered, the observed association between RTN and BP is weak and further flattened by methodological issues of primary studies, but its long-term consequences should not be ignored.