Middle-term nitrogen dioxide exposure and electrocardiogram abnormalities: A nationwide longitudinal study

Recently, professionals, such as those from the World Health Organization, have recommended a rigorous standard for nitrogen dioxide (NO₂), a typical urban air pollutant affected by regular traffic emissions, based on its short-term and long-term cardiorespiratory effects. However, the association between middle-term NO₂ exposure and cardiovascular disorders remains unknown.

This study was conducted to examine the relationship between NO₂ exposure and its middle-term cardiovascular risks indicated by electrocardiogram (ECG) abnormalities.

We included 61,094 subjects (132,249 visits) with repeated ECG observations based on longitudinal data from the China National Stroke Screening Survey (CNSSS). The NO₂ exposure concentration was derived from a predictive model, measured as the monthly average concentration in the 6 months of preceding the ECG measurement. We used the generalized estimation equation to assess the association between NO₂ exposure and ECG abnormalities.

For each 10 µg/m³ increase in monthly average NO₂ concentration, the odds ratio of ECG abnormalities was 1.10 (95% confidence interval [CI] 1.09-1.12) after multiple adjustments. Stratified regression analyses of urban and rural residents showed associations between middle-term NO₂ exposure and ECG abnormalities in urban (OR 1.09 [95% CI 1.08-1.11]) and rural residents (OR 1.14 [95% CI 1.10-1.19]). The association was robust within different subpopulations. Associations generally remained statistically significant (OR 1.03 [95% CI 1.02-1.05]) after extra adjustment for PM_2.5. Exposure-response relationship analysis revealed a nearly linear relationship between NO₂ exposure and the risk for ECG abnormalities.

Using the variation in ECG signals as a potentially reversible indicator for subclinical risk in cardiovascular systems, our study provides additional evidence on the increased risk posed by middle-term NO₂ exposure. Our study showed that policies controlling for NO₂ concentrations are beneficial to prevent cardiovascular diseases among Chinese adults.