Criteria air pollutants and hospitalizations of a wide spectrum of cardiovascular diseases: A nationwide case-crossover study in China

Few national studies have systemically examined the effects of criteria air pollutants on cardiovascular morbidity. This study aimed to investigate the associations between all criteria air pollutants and hospitalization of cause-specific cardiovascular diseases (CVD) in China. We obtained data on CVD hospitalization events of four major categories and 12 specific diseases from 153 hospitals distributed in 20 provincial-level regions from 2013 to 2020. We adopted a time-stratified case-crossover study design using individual cases to capture the effect of short-term exposure to six criteria air pollutants on CVD hospitalizations, using conditional logistic regression models. More than 1.1 million CVD hospitalization events were included. The lag pattern exploration demonstrated the largest effect for six air pollutants on lag 0–1 day. PM_2.5, PM₁₀, NO₂, and CO were significantly associated with increased hospitalization from ischemic heart diseases, cerebrovascular diseases, other heart diseases, and five specific causes of CVD. The effect estimates of NO₂ were the most robust when adjusting for co-pollutants. The concentration-response curves were positive and linear for most pollutant–endpoint pairs (except for O₃), and these positive associations remained even below the 24-h levels recommended by WHO Air Quality Guidelines and China Air Quality Standards. This nationwide case-crossover study in China demonstrated that short-term exposure to multiple ambient air pollutants may significantly increase the risk of cause-specific CVD hospitalizations even under the most stringent air quality regulations, striking an alert for potential CVD patients against these environmental risk factors.