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

Abstract

Background: Previous studies have shown that exposures to ambient particulate matter with aerodynamic diameter <2.5 μm (PM_2.5) and stress are associated with adverse cardiovascular health effects.

Objectives: To investigate the potential modifying effect of trait anxiety on the association between short-term exposures to PM_2.5 and HRV variables.

Methods: 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.

Results: Data on 87 participants were included in final analysis after exclusions. Higher exposure to PM_2.5 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 PM_2.5 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 PM_2.5 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).

Conclusion: Our study suggests that trait anxiety could modify the association of short-term exposure to PM_2.5 with HRV variables, indicating that higher trait anxiety may increase the cardiac susceptibility to air pollution in the study participants.

Keywords: Air pollution; Heart rate variability; Modifying effect; Particulate matter; Trait anxiety.