Long-term exposure to road traffic noise and cause-specific mortality: a Danish Nurse Cohort Study

Abstract

Background. There is growing evidence on the adverse effect of road traffic noise exposure on cardio- and cerebrovascular disease and diabetes morbidity, with limited data on mortality. We investigated whether long-term exposure to road traffic noise was associated with all-cause and cause-specific mortality. Methods. We linked 24,698 female nurses from the Danish Nurse Cohort, who at recruitment in 1993 or 1999 reported information on lifestyle, to the Danish Register of Causes of Death until the end of 2013. Road traffic noise levels in 1970-2013 were estimated by Nord2000 model as the annual mean of a weighted 24h average (Lden). We examined the associations between up to 23-year mean exposure to Lden and mortality using time-varying Cox regression models, adjusting for individual characteristics and particulate matter with diameter < 2.5 µg/m3 (PM2.5). Results. During the mean follow-up of 17.5 years, 3,779 nurses died in total: 882 from cardiovascular disease (CVD), 277 from stroke, 76 from diabetes, 222 from dementia, 323 from respiratory disease (RD), and 1594 from cancer. Compared to a 5-year mean Lden < 48 dB, fully adjusted hazard ratios (95% confidence intervals) for all-cause mortality were 1.13 (1.02-1.25) and 1.14 (1.02-1.28) for exposure levels between 48-58 dB and > 58 dB, respectively. Corresponding estimates for CVD mortality were 1.23 (0.99-1.54) and 1.30 (1.02-1.67), for stroke mortality 2.01 (1.27-3.18) and 1.94 (1.17-3.22), for diabetes mortality 1.15 (0.54-2.48) and 1.53 (0.65-3.57), for dementia mortality 1.38 (0.84-2.26) and 1.36 (0.79-2.36), for RD mortality 1.20 (0.82-1.74) and 1.20 (0.79-1.84), and cancer mortality 1.01 (0.87-1.17) and 1.04 (0.88-1.24), respectively. HRs with 23-year mean of Lden were enhanced for all-cause and diabetes mortality, but attenuated for CVD, stroke, RD and dementia mortality. Conclusion: Long-term exposure to road traffic noise may increase risk of premature mortality independent of air pollution.