Exposure to road traffic noise has been linked to adverse health effects, including cardiovascular diseases (CVD), however, evidence is inconsistent. In this study we examined the association between long-term exposure to road traffic noise and incidence of myocardial infarction (MI).Methods
We used the data from a nationwide Danish Nurse Cohort on 22 438 female nurses (age >44 years) who at recruitment in 1993 or 1999 reported information on CVD risk factors. We obtained data on incidence of MI from the Danish National Patient Register until end of 2014. Road traffic noise levels at the nurses’ residences between 1970 and 2014 were estimated using The Nord2000 as the annual mean of a weighted 24 hour average (Lden). We used time-varying Cox regression models to examine the association between 24-, 10-, and 1 year running mean of Lden and MI incidence, in a crude model (adjusted for age and time of cohort enrolment) and in a fully adjusted model (adjusted for age, enrolment year, physical activity, alcohol, smoking, marital status, fruit consumption and use of hormone therapy).Results
Of the 22 438 women, 590 developed MI during a mean follow-up of 18.3 years. Residential road traffic noise levels ranged from 5–82.7 dB at the year of cohort baseline. We found no association between exposure to road traffic noise and MI in crude (hazard ratio; 95% confidence interval: 0.94; 0.83–1.05) or fully (0.92; 0.82–1.04) adjusted model, for each 10 dB increase in 24 year mean road traffic noise levels. Similar results were found with 10 year and 1 year exposure windows. We observed a possible trend of increased risk, although statistically non-significant, in nurses living in urban areas (1.29; 0.84–2.00), and none in those living in provincial (0.98; 0.77–1.23) or rural (0.91; 0.77–1.07) areas (p for interaction 0.38).Conclusion
We found no association between long-term exposure to road traffic noise and MI in the total population of Danish nurses. We present novel finding that nurses living in urban areas may be more susceptible to the effects of exposure to road traffic noise with respect to MI.