Transportation noise and risk of stroke: a nationwide prospective cohort study covering Denmark

Background Studies on transportation noise and incident stroke are few and inconclusive. We aimed to investigate associations between road-traffic and railway noise and the risk of incident stroke in the entire Danish population. Methods We estimated road-traffic and railway noise (Lden) at the most and least exposed façades for all residential addresses across Denmark (2.8 million) for the period 1990–2017. Based on this, we estimated the 10-year time-weighted mean noise exposure for 3.6 million Danes aged >35 years, of whom 184 523 developed incident stroke during follow-up from 2000 to 2017. Analyses were conducted using Cox proportional-hazards models, with adjustment for various individual- and area-level demographic and socio-economic covariates collected from registries and air pollution [fine particulate matter with particles with a diameter of ≤2.5 µm (PM2.5) and nitrogen dioxide (NO2)]. Results A 10-dB increase in the 10-year mean road-traffic noise at the most exposed façade was associated with an incidence rate ratio (IRR) of 1.04 [95% confidence interval (CI): 1.03–1.05] for all strokes. For road-traffic noise at the least exposed façade, the IRR per 10 dB was 1.03 (95% CI: 1.02–1.04) for all strokes. Railway noise was not associated with a higher risk of stroke. Conclusion Road-traffic noise increased the risk of stroke. These findings add to the evidence of road-traffic noise as a cardiovascular risk factor.