Association between Short-Term Exposure to Ozone and Heart Rate Variability: A Systematic Review and Meta-Analysis

At present, ambient air pollution poses a significant threat to patients with cardiovascular disease (CVD). The heart rate variability (HRV) is a marker of the cardiac autonomic nervous system, and it is related to air pollution and cardiovascular disease. There is, however, considerable disagreement in the literature regarding the association between ozone (O₃) and HRV. To further investigate the effects of short-term exposure to O₃ on HRV, we conducted the first meta-analysis of relevant studies. The percentage change of HRV indicator(s) is the effect estimate extracted for the quantitative analysis in this study. In our meta-analysis, per 10 ppb increase in O₃ was significantly associated with decreases in the time-domain measurements, for standard deviation of the normal-to-normal (NN) interval (SDNN) -1.11% (95%CI: -1.35%, -0.87%) and for root mean square of successive differences (RMSSD) -3.26% (95%CI: -5.42%, -1.09%); in the frequency-domain measurements, for high frequency (HF) -3.01% (95%CI: -4.66%, -1.35%) and for low frequency (LF) -2.14% (95%CI: -3.83%, -0.45%). This study showed short-term exposure to O₃ was associated with reduced HRV indicators in adults, which suggested that the cardiac autonomic nervous system might be affected after O₃ exposure, contributing to the association between O₃ exposure and CVD risk.