Personal coronary risk profiles modify autonomic nervous system responses to air pollution

Objective: We investigated whether PM2.5-mediated autonomic modulation depends on individual coronary risk profiles. Methods: Five-minute average heart rate (HR) and heart rate variability (HRV, including standard deviation of normal-to-normal intervals [SDNN], square root of the mean squared differences of successive NN intervals [rMSSD], high frequency [HF]) were measured from 24-hour ambulatory electrocardiograms, and personal PM2.5 exposures were monitored in a prospective study of 10 male boilermakers (aged 34.3 +/- 8.1 years). We used the Framingham score to classify individuals into low (score = 1-3) and high (score = 5-6) risk categories. Mixed-effect models were used for statistical analyses. Results: Each I-mg/m(3) increase in the preceding 4-hour moving average PM2.5 was associated with HR increase (5.3 beats/min) and HRV reduction (11.7%, confidence interval [CI] = 62-17.1% for SDNN; 11.1%, CI = 3.1-19.1% for rMSSD; 166%, CI = 1.5-31.7% for HF). Greater responses (2- to 4-fold differences) were observed in high-risk subjects than in low-risk subjects. Conclusions: Our study suggests that adverse autonomic responses to metal particulate are aggravated in workers with higher coronary risk profiles.