The impact of noise on the short-term effects of traffic-related air pollution on heart rate variability in young healthy adults

Abstract

Background: Traffic-related air pollution and noise are associated with cardiovascular diseases, and the alternation of heart rate variability (HRV), which reflects cardiac autonomic function, is considered as one of the mechanisms. However, few studies have explored interaction effects between traffic-related air pollution and noise on HRV. Aims: We explored whether noise modified the associations between short-term exposure to traffic-related air pollution and HRV in young healthy adults. Methods: In this randomized, crossover study, 40 young healthy adults stayed for 2 hours in a traffic center, and on a separate occasion, in a park. Subjects underwent ambulatory electrocardiogram monitoring and their personal exposure to fine particle (PM2.5), black carbon (BC), carbon monoxide (CO) and noise were measured. Mixed-effects regression models were applied for analysis, and interaction effects were assessed. Results: Traffic-related air pollution and noise were negatively associated with HRV separately, and the effects of traffic-related air pollutants were amplified at high noise level (>65.6 dBA) compared with low noise level (?65.6 dBA). Per 10 ?g/m3 increment in PM2.5 (5-minute moving average) was associated with ?4.61% (95% CI, ?6.75% to ? 2.42%) decrease in high frequency (HF) power, however the correlations became insignificant at low noise level. Per 1 ?g/m3 increment in BC (1-hour average) was associated with ?2.59% (95% CI, ?4.43% to ?0.72%) decrease in HF at high noise level, compared with ?2.20% (95% CI, ?3.56% to ?0.81%) at low noise level. Similar effects modification was observed for CO exposure. Conclusions: Both traffic-related air pollutants and noise associated with imbalanced cardiac autonomic function. The effects of air pollutants were amplified at high noise level.