The Effect Of Short-term Exposure To Ambient Air Pollutants On Adult Outpatient Visits For Symptoms Owing To Helicobacter Pylori Infection:A Case-Crossover Study

Background:Helicobacter pylori（Hp）infection is an important risk factor for gastrointestinal diseases,and Hp infection is one of the most prevalent bacterial infections in the world,and the prevalence of Hp infection in China is around 40%-90%.Hp infection is prolonged and prone to recurrence,seriously endangering the health of the organism,and early and effective prevention remains a difficult clinical problem.Current research suggests that Hp,as an inflammatory disease,is influenced by a combination of internal and external environmental factors,but there is still a lack of research on the effects of atmospheric pollutants on Hp infection.Therefore,it is of great public health importance to actively explore the pathways of Hp infection,risk factors and mechanisms.Objectives:To investigate the effect of short-term exposure to ambient air pollutants on the outpatient visits for adult HPI.Methods:The daily outpatient data from 1^stJanuary 2014 to 31^stMay 2021（2709 days）were obtained from the 901st Hospital of the Joint Logistics Support Force of the Chinese People’s Liberation Army.Based on the International Classification of Diseases（ICD-10）,with codes A49.812,the daily outpatient visits for HPI referred to the patients who were initially or previously diagnosed at the department of Gastroenterology.For further analyses,we divided all subjects into different subgroups,including age groups（<45 years vs.≥45 years）,sex groups（male vs.female）and medical insurance groups（yes vs.no）.The whole study periods were also divided into two seasons,warm season（April to September）and cold season（January to March and October to December）.Data of particulate matter with an aerodynamic diameter no greater than 2.5 or 10micrometers(PM_2.5,PM₁₀),sulfur dioxide（SO₂）,nitrogen dioxide（NO₂）,carbon monoxide（CO）and ozone（O₃）were obtained from the Department of Ecology and Environment of Anhui Province（https://sthjt.ah.gov.cn/site/tpl/5391?city Code=340100）.Meantime,we obtained the daily values of temperature and relative humidity from the China Meteorological Data Service Center（http://data.cma.cn/）.A time-stratified case-cross analysis was used to explore the correlation between air pollutant exposure and HPI outpatient visits.Conditional logistic regression model was used to control the time-invariant individual-level confounding factors.The statistical differences of various exposure factors between different subgroups were used for Z-test.Build a dual-pollutant model and draw an exposure response（E-R）curve to evaluate the relationship between air pollutants and HPI outpatient visits.All analyses were conducted in R software（version 4.0.4）with packages“mgcv”and“dlnm”.The results were expressed by odds ratio（OR）of HPI outpatient visits at 75th and 95th percentile of air pollutants concentrations against the threshold of air pollutants.Results:1.After excluding the lost patients（n=1288）,a total of 9072 outpatients met the enrollment requirements.During the whole study period（2709 days）,3.35outpatient visits were recorded on average every day,with male and female accounting for 52.1%and 47.9%respectively;50.2%and 49.8%of patients under 45 years old and≥45 years old respectively;The proportion of outpatient service in warm season and cold season was 53.2%and 46.8%respectively;Individuals with and without medical insurance accounted for 69.3%and 30.7%respectively.2.The daily average maximum 8-hour average level of O₃is 90.5μg/m³,the 24-hour average concentrations of PM_2.5,PM₁₀,SO₂,NO₂and CO are 45.7μg/m³、72.4μg/m³、9.3μg/m³、41.3μg/m³and 0.8 mg/m³respectively.3.There is a significant correlation between daily air pollution concentration and weather conditions in Hefei,China（P<0.01）.4.The exposure-response curve of the single pollutant model showed that when NO₂,SO₂and CO exceeded the threshold（the lowest risk concentration of air pollution）,the air pollution factor was positively correlated with the number of HPI outpatient visits and had statistical significance（P<0.05）,while exposure to PM or O₃was not correlated with the number of HPI outpatient visits.5.The threshold of NO₂with a delay of 0 days is 37μg/m³,the threshold value of SO₂with 0 days lag is 8μg/m³,the threshold of CO for 0 days lag is 0.8 mg/m³.The three air pollutants above the threshold are related to the increased risk of HPI outpatient visits.The ORs of the 75th percentile HPI outpatient visits and the threshold are:NO₂is1.082（1.036–1.131）,SO₂is 1.061（1.024–1.098）,CO is 1.063（1.019–1.110）;The corresponding ORs of the 95th percentile and threshold of NO₂,SO₂and CO are 1.207（1.120–1.302）,1.175（1.052–1.312）and 1.110（1.019–1.209）,respectively.6.After adjusting other air pollutants,the correlation between air pollution and the number of HPI outpatient visits is consistent with the single pollution model.7.Among the demographic characteristics,male exposure to HPI at the 75th and 95th percentiles of NO₂increased（P<0.05）;Women were exposed to HPI at the 75th percentile and 95th percentile of NO₂,SO₂and CO（P<0.05）.Patients younger than 45years old were exposed to HPI at the 75th percentile,95th percentile and 95th percentile of NO₂（P<0.05）45-year-old patients were exposed to HPI at the 75th percentile of NO₂,95th percentile of SO₂and 75th percentile of CO（P<0.05）.The risk of HPI visits exposed to the 75th percentile of NO₂,the 95th percentile of SO₂and the 95th percentile of SO₂in warm season increased（P<0.05）;The risk of HPI visits exposed to the 95th percentile of NO₂,the 75th percentile of SO₂and CO and the 95th percentile of CO in cold season increased（P<0.05）.Patients without medical insurance were exposed to HPI at the 75th and 95th percentiles of NO₂and SO₂（P<0.05）;The risk of HPI in the 75th percentile and 95th percentile of NO₂,SO₂and CO exposure of those with medical insurance increased（P<0.05）.Conclusions:Short-term exposure to environmental NO₂,SO₂and CO may lead to an increase in the number of outpatient visits with simultaneous HP infection.The results of the exposure-response curve were positively correlated,and showed obvious threshold effect on NO₂,SO₂and CO.Some characteristics including age,sex,season and medical insurance,do not change the risk of air pollution on HPI outpatient visits,and the risk of HPI outpatient visits is higher when the age is≥45 years old,women,patients with medical insurance and exposed to air pollution in cold season.