Short-term air pollutants exposure has heterogeneous associations with intracerebral hemorrhage risk: A case-crossover study based on symptom onset time in Chengdu, China

Background: The association between air pollutants and intracerebral hemorrhage (ICH) risk is inconsistent. Most previous research focuses on admission rather than symptom onset. In the present work, we used symptom onset time to explore the relationship between short-term air pollutants exposure and ICH risk in Chengdu, China.& nbsp;Methods: We adopted a time-stratified case-crossover approach to study the association between six air pollutants exposure (PM2.5, PM10, SO2, NO2, CO & O-3) and ICH risk in a teaching hospital, which covers a population of more than one million. Subgroup analysis was conducted and stratified by individual factors, including sex, age, and medical history.& nbsp;Results: We ultimately enrolled 1052 cases in this study. Overall, the daily concentration elevation of PM2.5, PM10, SO2, and CO in lag4 increased ICH risk. And the OR were 1.027 (95% CI 1.004 to 1.050), 1.017 (95% CI 1.003 to 1.031), 1.018 (95% CI 1.003 to 1.032), and 1.040 (95% CI 1.013 to 1.068), respectively. In subgroup analysis, increases of PM2.5 and PM10 promoted the ICH risk in patients < 60 years old, and elevation of SO2 and NO2 upped the ICH risk in patients >= 60 years old. CO increased the ICH risk of male patients; NO2 was associated with reduced risk in female patients and increased risk in cases with non-smoking or non-drinking. PM2.5, PM10, SO2, and CO raised the ICH risk of patients with non-smoking, non-drinking, non-diabetes, or hypertension. The smoking or hypertension cases had greater OR after exposure to O-3.& nbsp;Conclusions: Short-term air pollutants exposure has heterogeneous associations with ICH risk, and the connections are different in the overall cases and subgroups. Further studies are needed to clarify the biological association between specific pollutants and ICH risk.