Residential road traffic noise exposure and survival after breast cancer - A cohort study

Background: It is generally acknowledged that patients with already existing clinical conditions are especially vulnerable to the effects of traffic noise exposure. The aim of the present study was to investigate the association between residential road traffic noise and breast cancer survival. Methods: Road traffic noise was calculated for all residential addresses from 1987 to February 2012 for incident breast cancer cases (n=1,759) in a cohort of 57,053 Danes. We used Cox Proportional Hazard Models to investigate the association between residential road traffic noise at different time-windows, and overall and breast cancer-specific mortality. Furthermore, we investigated interaction with prognostic and socioeconomic factors. Mortality Rate Ratios (MRR) were calculated in both unadjusted models, and adjusted for residential railway noise, lifestyle factors and socioeconomic variables. Results: During a median of 7.3 years of follow-up, 402 patients died; 274 from breast cancer. We found no association between time-weighted averages of residential road traffic noise 1-, 3- or 5-years before death, or over the entire follow-up period, and overall or breast cancer-specific mortality. A 10 dB higher road traffic noise from diagnosis until censoring was associated with an adjusted MRR of 0.94 (0.81-1.08) for all-cause mortality. The association was modified by lymph node involvement, with a MRR of 1.20 (0.97-1.48) for those with tumor-positive lymph nodes and 0.76 (0.59-0.98) for those without. Conclusion: The present study suggests no association between residential road traffic noise and concurrent mortality. As it is the first study of its kind, with relatively limited power, further studies are warranted.