Objective To investigate the effects of indoor and outdoor air pollution on electrocardiogram (ECG) parameters and their interaction among government employees in Hunan Province, China.

Methods The study population comprised a total of 2014 participants who were randomly selected by age and sex stratification from government employees who had undergone health check-ups at a tertiary general hospital in Hunan Province from January 2018 to April 2020. A standard questionnaire was employed to investigate information on indoor air pollution, including home decoration, cooking frequency, fuel type, number of cohabitants, and home area, as well as the basic characteristics of the subjects. Personal exposure levels to outdoor air pollutants (including PM_2.5, PM₁₀, SO₂, NO₂, and CO) were calculated using the inverse distance weighting method based on the subjects' home and workplace addresses. The standard resting 12-lead ECG test was performed in accordance with established protocols. The associations of indoor/outdoor air pollution with ECG results were assessed by using generalized linear models. Furthermore, multiplicative interaction and subgroup analyses were performed to elucidate the interaction between indoor and outdoor air pollution on ECG parameters.

Results For the 2014 government employees, the median age was 34.0 years, and 76.3% of them were females. After adjusting for covariates, the use of unclean cooking fuel was associated with an increased heart rate. A greater number of cohabitants was associated with a prolonged P-wave duration and a prolonged QTc interval. Home area was negatively associated with the electrical axis. Both PM_2.5 and PM₁₀ were negatively associated with QTc interval. SO₂ had a negative association with P-wave duration while a positive association with the electrical axis. NO₂ was positively associated with P-wave duration. The multiplicative interaction analyses indicated significant interactions between the number of cohabitants and outdoor SO₂ exposure (P_interaction=0.003), PM_2.5 exposure (P_interaction=0.007), and NO₂ exposure (P_interaction=0.042) on P-wave duration; the subgroup analysis indicated that compared with more than 3 cohabitants, when the number of cohabitants was ≤3, the effects of SO₂ (β=-2.71, 95% confidence interval CI: -4.45 to -0.97) and NO₂ (β=2.84, 95%CI: 1.10 to 4.57) on P-wave duration remained significant. There was a significant interaction between outdoor PM₁₀ exposure and home area (P_interaction=0.032) on QTc interval; the subgroup analysis indicated that the subgroup differences were significant for home area ≤115 m² compared with home area >115 m² (β=-2.72, 95%CI: -5.02 to -0.41).

Conclusion Indoor and outdoor air pollution are associated with changes in ECG parameters including heart rate, P-wave duration, QTc interval, and the electrical axis, with multiplicative interactions on P-wave duration and QTc interval.