Association between short-term exposure to ambient air pollution and number of outpatient Helicobacter pylori infection visits

Helicobacter pylori infection (HPI) is an important risk factor of gastrointestinal diseases, but factors leading to it are still not fully understood. To investigate the association between short-term exposure to air pollution and HPI during outpatient visits, we collected daily data for HPI outpatient visits and air pollutant concentrations during 2014-2021 in Hefei, Anhui Province, China. A time-stratified case-crossover design was performed to analyze the acute impacts of air pollution on HPI outpatient visits. We also explored potential effect modifiers. A total of 9072 outpatient visits were recorded. We found positive and statistically significant associations of acute exposure to nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO) with HPI outpatient visits. Threshold concentrations of the three pollutants with same-day exposure (lag 0 day) for outpatient visits were 37 mu g/m(3) for NO2, 8 mu g/m(3) for SO2, and 0.8 mg/m(3) for CO. The odds ratios for HPI outpatient visits at the 95th percentile of NO2, SO2, and CO against the thresholds were 1.207 (1.120-1.302), 1.175 (1.052-1.312), and 1.110 (1.019-1.209), respectively. The associations were more evident in patients older than 45 years, females, with health insurance, and in cold seasons. Null associations of exposure to either ozone (O-3) or particulate matter (PM) were observed. In summary, short-term exposure to NO2, SO2, and CO above certain concentrations, but not PM or O-3, may trigger the increased risk of outpatient visits due to HP infection in Chinese population.