Long-term exposure to road traffic noise and incident myocardial infarction: A Danish Nurse Cohort study

Abstract

Background: Evidence of nonauditory health effects of road traffic noise exposure is growing. This prospective cohort study aimed to estimate the association between long-term exposure to road traffic noise above a threshold and incident myocardial infarction (MI) in Denmark.

Methods: In the Danish Nurse Cohort study, we used data of 22,378 women, at recruitment in 1993 and 1999, who reported information on MI risk factors. The participants' first hospital contact or out-of-hospital death due to MI were followed-up until 2014. We investigated a relationship between residential exposures to road traffic noise levels (L_den) up to 23 years and incident MI (overall, nonfatal, and fatal) using time-varying Cox regression models adjusting for potential confounders and air pollutants. We estimated thresholds of road traffic noise (53, 56, and 58 dB) associated with incident MI in a piece-wise linear regression model.

Results: Of the 22,378 participants, 633 developed MI, 502 of which were nonfatal. We observed a non-linear relationship between the 23-year running mean of L_den and incident MI with a threshold level of 56 dB, above which hazard ratios (95% confidence intervals) were 1.30 (0.97, 1.75) for overall and 1.46 (1.05, 2.03) for nonfatal MI per 10 dB. The association with nonfatal MI attenuated slightly to 1.34 (0.95, 1.90) after adjustment for fine particles.

Conclusions: We found that long-term exposure to road traffic noise above 56 dB may increase the risk of MI. The study findings suggest that road traffic noise above 56 dB may need regulation in addition to the regulation of ambient pollutants.

Keywords: Cohort study; Incidence; Myocardial infarction; Noise; Survival analysis; Threshold limit values.

Figure 1.

Relationship between (A) overall, (B) nonfatal, and (C) fatal incident MI and 23-year running mean of road traffic noise (24-hour weighted mean) in the Danish nurse cohort (N = 22,378). A relationship between 23-year exposure to road traffic noise and (A) overall, (B) nonfatal, (C) fatal incident MI in the Danish nurse cohort was expressed in a solid spline line with 95% CIs (dashed spline lines). Y-axis in the residual plot indicated HRs at certain L_den levels (ranged between 0 and 80 dB) compared to the risk at 56 dB of L_den. Gray vertical lines in the residual plots were drawn at 53 dB (a solid line), 56 dB (a dashed line), and 58 dB (a dotted line) of L_den. A histogram of the distribution of 23-year exposure to road traffic noise was drawn in light gray. Model adjusting for strata term of baseline year, a penalty spline term of calendar year, and individual- and area-level covariates.