Diurnal cardiac sympathetic hyperactivity after exposure to acute particulate matter 2.5 air pollution

Ambient fine particulate matter (PM2.5) exposure is associated with increased cardiovascular and cardiac arrhythmias events, but the detailed mechanism remains unclear.

We aimed to investigate the effect of PM2.5 (particulate matter < 2.5 μm in aerodynamic diameter) on the cardiac autonomics through a heart rate variability (HRV) analysis.

Among 6912 patients who had underwent 24-hour Holter ECG recordings between Oct 1st 2015 and Oct 31st 2016, 46 (25 males, 69.3 ± 12.1 years old) were enrolled with confirmation of living in an environment with a reported PM2.5 level and were classified as elevated (Group 1, >36 μg/m³, 50.73 ± 8.50) or low (Group 2, <11 μg/m³, 6.06 ± 1.00) PM2.5 group. The Holter recordings and HRV parameters were evaluated.

The baseline characteristics including the comorbidities and medications were similar between the 2 groups. The Holter ECG parameters were also similar. There were no significant HRV differences between the two groups for the 24-hour interval analysis. However, the LF/HF ratio was significantly higher in Group 1 than Group 2 in the 9 am to 9 pm (p = 0.028), 8 am to 4 pm (p = 0.024), and 4 pm to 12 pm (p = 0.025) periods, respectively, but not for the nocturnal HRV parameters.

Our study demonstrated that an elevated PM2.5 exposure had a significant association with an increased daytime LF/HF ratio suggesting a diurnal difference in the response to PM2.5 exposure.