The modifying effect of trait anxiety on the association of fine particulate matter with heart rate variability variables

Previous studies have shown that exposures to ambient particulate matter with aerodynamic diameter <2.5 μm (PM2.5) and stress are associated with adverse cardiovascular health effects.To investigate the potential modifying effect of trait anxiety on the association between short-term exposures to PM2.5 and HRV variables.A panel of 92 middle-aged and elderly adults in Tianjin and Shanghai were recruited for repeated follow-ups with measurements of 24-h personal exposures to air pollutants and Holter ECG monitoring. Heart rate variability (HRV) variables calculated over 5-minute segments during the 24 h, including low frequency power (LF), high frequency power (HF), standard deviation of normal-to-normal intervals (SDNN) and root mean square of successive differences (rMSSD), were included in the analysis. The Trait Anxiety Inventory was used to investigate the long-term general anxiety level of the participants. Generalized linear mixed-effects model was used to analyze the association between exposure factors and HRV variables, and potential effect modification by trait anxiety.Data on 87 participants were included in final analysis after exclusions. Higher exposure to PM2.5 was associated with lower levels of LF, HF, SDNN and rMSSD, and the largest decreases in LF, HF, SDNN and rMSSD were found at 3-h moving average. Trait anxiety significantly modified the associations of PM2.5 with LF, HF, SDNN and rMSSD, with stronger inverse associations found in high trait anxiety group than in low trait anxiety group. For an IQR (27.3 μg/m³) increase in PM2.5 at 3-h moving average, there were decreases of 3.50% (95% CI: -4.46%, -2.54%) and 3.50% (95% CI: -4.49%, -2.50%) in the high trait anxiety group, and decreases of 0.81% (95% CI: -1.22%, -0.40%) and 0.65% (95% CI: -1.07%, -0.23%) in the low trait anxiety group in HF and rMSSD, respectively (both p for interaction<0.01).Our study suggests that trait anxiety could modify the association of short-term exposure to PM2.5 with HRV variables, indicating that higher trait anxiety may increase the cardiac susceptibility to air pollution in the study participants.