Exposure to road traffic and railway noise and postmenopausal breast cancer: A cohort study

Exposure to traffic noise may result in stress and sleep disturbances. Studies on self-reported sleep duration and breast cancer risk have found inconsistent results. In a population-based Danish cohort of 29,875 women aged 50-64 years at enrolment in 1993-1997, we identified 1219 incident, postmenopausal breast cancer cases during follow-up through 2010. Mean follow-up time was 12.3 years. Road traffic and railway noise was calculated for all present and historical residential addresses from 1987 to 2010. We used Cox proportional hazard model for analyses and adjusted for hormone replacement therapy use, parity, alcohol consumption and other potential confounders. We found no overall association between residential road traffic or railway noise and breast cancer risk. Among women with estrogen receptor negative breast cancer, a 10-dB higher level of road traffic noise (continuous scale) during the previous 1, 5 and 10 years were associated with 28% (95% CI: 1.04-1.56), 23% (95% CI: 1.00-1.51) and 20% (95% CI: 0.97-1.48) higher risks of estrogen receptor negative breast cancer, respectively, in fully adjusted models. Similarly, a 10-dB increase in railway noise (1-year mean at diagnosis address) increased risk for estrogen receptor negative breast cancer by 38% (95% CI: 1.01-1.89). There was no association between road traffic or railway noise and estrogen receptor positive breast cancer. In conclusion, these results suggest that residential road traffic and railway noise may increase risk of estrogen receptor negative breast cancer. As the first study on traffic noise and breast cancer results should be treated with caution. What's new? Urbanization is linked to increased traffic noise, exposure to which is associated with stress and sleep disturbances. However, the impact of sleep duration and traffic noise exposure on breast cancer risk remains unclear. The present study suggests that residential exposure to road traffic and railway noise is associated with a dose-dependent increase in risk for estrogen receptor negative breast cancer. Exposure to road traffic and railway noise is considerable in many parts of the world, including the European Union, where more than 30% of the population is exposed to road traffic noise at levels exceeding WHO guideline values.