Introduction: Fine particulate (PM2.5) air pollution has been associated with impaired cardiac autonomic modulation (CAM) in adults. The association between PM2.5 exposure and CAM in adolescents is rarely investigated.
Hypothesis: We assessed the hypothesis that PM2.5air pollution is related to acute impairment of CAM in adolescents.
Methods: We used data from 421 adolescents in the Penn State Child Cohort follow-up examination. We obtained 24-hour ECG data using a 12-lead Holter ECG from each participant. After removing artifacts and arrhythmic beats, we performed heart rate variability (HRV) analysis on normal RR intervals to compute 30-min based high frequency (HF) and low frequency (LF) powers, standard deviation of RRs (SDNN), and the square root of mean of the sum of the squared differences of the adjacent RRs (RMSSD). Individual level 24-hour PM2.5 concentration was obtained by a personal PM2.5 monitor. We then calculated, on a 30-min basis, the corresponding time-specific exposure to PM2.5. Distributed lag models under a framework of linear mixed-effects model, with a first-order autoregressive covariance structure, were used to assess the segment-specific and cumulative effect of 30-min based PM2.5 and HRV indices.
Results: As shown in the table, both individual lag and cumulative effects of PM2.5 on HRV, based on the lag 0-6 model, were significant after controlling for major covariates. For instance, for a 10 μg/m3 increase in cumulative PM2.5, HF and SDNN decreased by 0.023 (SE=0.006) ms2 and 0.61 (SE=0.16) ms, respectively. A 10 μg/m3 increase in PM2.5 was also significantly associated with elevated heart rate (0.25 (SE=0.09) beat/min). Individual lag effects of PM2.5 were most consistently associated within 1.5 hours.
Conclusion: Individual level exposure to PM2.5 in adolescents is associated with impaired CAM, towards an elevated sympathetic and decreased parasympathetic outflow. The time to the apparent cumulative effect is about 3 hours, with the most consistent individual lag effects within 1.5 hours.