Exposure-response relationship between traffic noise and the risk of stroke: a systematic review with meta-analysis

Traffic noise is an established risk factor for some cardiovascular diseases such as hypertension and ischaemic heart disease, but the evidence regarding stroke is still limited. In this study we aimed to systematically review the related epidemiological data and make a meta-analysis of the risk of stroke morbidity associated with road and air traffic noise exposure. We searched articles in English, Spanish, and Russian indexed in MEDLINE, EMBASE, and Google Scholar on 24 November 2015. Qualitative synthesis was made for 13 studies, and 11 studies were included in quality effects meta-analyses. Overall, they were of high quality. Based on six studies (n≈8,790,671 participants) for road traffic noise, we found a pooled relative risk (RR) of stroke per 10 dB to be 1.01 (95 % CI: 0.96, 1.06). In the 70-75 dB noise range (versus <55 dB) RR increased to 1.29 (95 % CI: 0.74, 2.24). For air traffic noise we pooled five studies (n≈16,132,075 participants) and the RR per 10 dB was 1.01 (95 % CI: 1.00, 1.02). Road traffic group showed high heterogeneity whereas the air traffic group had none. Both groups showed evidence of publication bias. In conclusion, we have established a small but elevated risk of stroke to be associated with both road and air traffic noise exposure, but the association was statistically significant only with the latter. The effect of road traffic noise followed a non-linear trend.