Table 3.

RRs (95% CI) and P Values in Associations Between 10 μg/m³ Increments of PM_2.5 Concentrations and Cardiac Arrhythmia Counts^*

	PAC		PVC
	RR (95% CI)	P value	RR (95% CI)	P value
Lag 0, instantaneous	0.995 (0.989, 1.002)	0.17	0.998 (0.983, 1.013)	0.76
Lag 1, 0.5–1.0 h prior	0.998 (0.990, 1.003)	0.25	1.015 (1.004, 1.027)	<0.01
Lag 2, 1.0–1.5 h prior	1.000 (0.995, 1.006)	0.88	1.022 (1.011, 1.033)	<0.01
Lag 3, 1.5–2.0 h prior	1.003 (0.998, 1.009)	0.24	1.016 (1.002, 1.029)	0.02
Cumulative, within 2.0 h	0.989 (0.970, 1.009)	0.27	1.051 (1.002, 1.102)	0.04

All models were adjusted for age, race, sex, body mass index percentile, temperature, and relative humidity. P values for zero‐, first‐, and second‐degree polynomial terms were 0.76, <0.01, and <0.01, respectively. PAC indicates premature atrial contraction; PM_2.5, fine particles with aerodynamic diameters ≤2.5 μm; PVC, premature ventricular contraction; and RR, rate ratio.

^*RRs were calculated by exponentiating the regression coefficients from distributed lag‐negative binomial models. An RR of 1.05 indicates a 5% increase in arrhythmia counts/30 min in association with a 10 μg/m³ increase in PM_2.5 concentration.