The Association Between Biomass Exposure And Chronic Obstructive Pulmonary Disease Among Chinese Women

BackgroundChronic Obstructive Pulmonary Disease(COPD)is a preventable chronic respiratory disease and,often with progressive development,is characterized by incompletely reversible airflow limitation[1].It is also associated with abnormal inflammatory reactions of harmful gases and harmful particulates in the lungs[1].Besides,COPD often has a negative impact on the living quality of patients.Indoor air pollution caused by the combustion of coal and biofuels is an importantreason of disease which burdens low and middle income countries.The WHO estimates that indoor air pollution caused 4.3 million deaths in 2012[2].Smoke from biofuel combustion is a main source of indoor air pollution in developing countries.In addition,indoor air pollution caused by biofuels has become a vital issue and it may pose a threat to the public health.Indoor air pollution caused by biofuels is associated with various respiratory systems and cardiovascular and cerebrovascular diseases,of which the greatest impact is on chronic obstructive pulmonary disease.More and more evidences show that the use of biofuels for life energy is closely related to the pathogenesis of chronic obstructive pulmonary disease especially for the women in low and middle income countries and it is an important hazard for COPD[3-6].In developing countries,about 50%COPD death,about 75%of which are women,are attributed to biofuel smoke[7].The smoking rate of women is much lower than that of men in China[8].Further,women have more opportunities to cook and are more likely to expose to biofuels for longer time.Therefore,the indoor air pollution caused by the burning of biofuels has a more significant effect on female chronic obstructive pulmonary disease.However,no study has been reported on the prevalence of biomass exposure to women in China.Also,there are fewer researches on the connection between biomass exposure and COPD in China.This may result from the fact that the present researches were conducted in relatively limited areas.Moreover,the confounding factors of these researches were also different,and the OR between biofuel exposure and the risk of COPD,currently,is not fully understood.Therefore,it is necessary to study the prevalence of biomass exposure among women in China and to analyze the hazard of biofuel exposure to female chronic obstructive pulmonary disease and lung function in China.Then this thesis aims to understand people's burden of biofuel exposure on COPD.It will also help to improve the emphasis on biofuels and provide evidence for the involved measures to reduce biofuel exposure and prevent COPD.Objective1.To describe and analyse the prevalence of cooking biomass exposure and the prevalence of COPD in Chinese women aged 40 or older.2.To explore the association between biomass exposure and chronic obstructive pulmonary disease among Chinese women aged 40 or older.3.To analyse the Population Attributable Risk Percent(PAR%)to female COPD who aged 40 or older.Methods1.Survey methods(1)Multi-stage stratified cluster random sampling method was used to select Participants aged 40 or older from 125 monitoring sites in 31 provinces/municipalities/municipalities in 2014-2015(living in the monitoring area for more than 6 months during the 12 months before the survey).When sampling,the national representativeness of the sample and the representativeness of the region(eastern,central and western)and urban and rural areas were all taken into consideration.The country was divided into 6 levels in accordance with the level of East,West,and urbanization,and the monitoring is distributed according to the proportion of counties in each layer.Then the COPD monitoring points were selected at each level of cause of death monitoring point.Finally,a total of 125 COPD monitoring sites were selected.Firstly,3 townships or streets were randomly selected from each monitoring site using a probability sampling method(PPS sampling)proportional to the population size.Secondly,2 villages/neighborhoods are sampled using PPS sampling in each township/street.Thirdly,1 village/residential group(at least 150 households)is randomly selected and in each village/neighborhood.Then one hundred households surveyed were selected from each village/residential group.Lastly,one aged 40 or above was randomly selected from each household using the KISH table method.In this study,a total of 37795 women were selected for the analysis.(2)The participants underwent a face-to-face questionnaire survey conducted by trained investigators with PAD.Questionnaire survey,height and weight measurements,and lung function tests were conducted among respondents.Questionnaire content mainly includes demographic data,personal and family history of illness,smoking history,exposure to secondhand smoke,the usage of cooking fuel,the type of cooking stove,the location of kitchen,kitchen exhaust equipment,the methods of winter heating,occupations exposure and contraindications for lung function tests.(3)COPD diagnostic criteria:According to the COPD diagnostic criteria recommended by GOLD(2017),the definition of epidemiological diagnosis of COPD in this study was established.That is,after inhaling bronchodilators in the subjects,lung function tests were performed.If the FEV1/FVC was less than 70%,it was confirmed that there was a continuous airflow limitation and the diagnosis was COPD.2.Statistic methodsSAS9.4 statistical software was used to clean up and analyze the data.(1)Based on complex sampling weights and post-stratification weights,the characteristics of biomass exposure are described.The difference of rate was evaluated by the Rao-Scott ?2 test based on complex sampling design correction.A logistic regression model with complex sampling design was used to directly include the level variable value as a continuous variable into the model in order to conduct a trend test of the rate.(2)The prevalence(%,95%CI)of COPD based on complex sampling weights and post-stratification weights was used to describe the prevalence of COPD among females with different characteristics.The difference of rate was evaluated by the Rao-Scott ?2 test based on complex sampling weights and post-stratification weights.(3)Using COPD as a dependent variable and whether or not biofuel exposure is an independent variable,univariate analysis was performed using univariate Logistic regression with complex sampling.And using complex sampling multivariate Logistic regression to further control other risk factors of COPD,explore the impact of biofuel exposure on the prevalence of COPD.(4)Percentage of population attributable risk(PAR%):PAR%= Pe*(OR-1)/(1+Pe*(OR-1))[9],Pe is the exposure rate of the population and OR is the odds ratio after correcting confounding factors from Logistic regression model.Results??The prevalence of cooking biomass exposure in Chinese women aged 40 or older1.A total of 37795 women were surveyed.After removing 18 samples that were both missing from the "whether to cook regularly" variable and the "whether using biofuels to cook" variable,37777 women were eventually included in this section.The study showed that the prevalence of cooking biomass exposure for Chinese women aged 40 years or older was 35.8%(95%CI:29.6%?42.1%),with significant difference observed in rural vs urban,i.e.51.9%(95%CI:44.2%?59.5%)in rural women and 18.2%(95%CI:13.1%?23.4%)in urban women(?2=121.99,P<0.0001).The results showed that the prevalence of cooking biomass exposure increased with age(the trend ?2=23.39,P<0.0001)and decreased with the increment of educational level(the trend x2=91.40,P<0.0001).2.The prevalence of cooking biomass exposure for Chinese women aged 40 years or older in the eastern,central and western rural regions increased in turn(x2=6.69,P=0.0353),highest in rural western areas(61.5%,95%CI:53.6%?69.5%).The prevalence of cooking biomass exposure for Chinese women were 54.5%(95%CI:42.8%-66.3%)and 41.3%(95%CI:27.2%?55.4%)in the central and eastern rural areas,respectively.3.Among the female population aged 40 and above in urban areas in the seven regions,the exposure rate of cooking biofuels for female population was 7.4%(95%CI:0.4%-14.4%)in North China,and 21.0%(95%CI:9.7%?32.3%)in East China,18.2%(95%CI:5.5%?30.8%)in Central China,25.3%(95%CI:6.5%?44.0%)in South China,16.4%(95%CI:7.7%?25.2%)in Southwest China,and 21.7%(95%CI:0.0%?45.3%)in Northwest China,23.1%(95%CI:6.9%-39.3%)in Northeast China(?2=5.45,P=0.4870).The difference in the exposure rate of female cooking biofuels in the rural areas of the seven regions was statistically significant(?2=41.59,P<0.0001).The prevalence of cooking biomass exposure was highest in the rural areas of northeastern China(88.9%,95%CI:85.5%?92.2%),68.5%(95%CI:57.0%?80.1%)in the rural areas of South China,23.8%(95%CI:4.5%?43.1%)in the rural areas of North China,lowest in urban areas of North China(7.4%,95%CI:0.4%?14.4%).4.The total proportion of ventilation equipment(hoods,exhaust fans or chimneys)installed in women's home kitchens in China was 75.3%(95%CI:71.2%?79.5%),and 24.7%(95%CI:20.5%?28.8%)of women's home kitchens are not equipped with any ventilation equipment.The proportion of kitchen ventilator installations in exposed and uncovered cooking biofuel households was 75.8%(95%CI:70.8%?80.9%)and 75.1%(95%CI:69.8%?80.3%),respectively,with no statistical difference(P=0.8244).The proportion of ventilators installed in kitchens exposed to cooking coal was 54.8%(95%CI:44.3%?65.3%),which was significantly lower than that of female households unexposed to cooking coal(78.2%,95%CI:74.7%?81.7%)(x2=48.43,P<0.0001).5.The total proportion of kitchens in the living room is 3.5%(95%CI:2.1%?4.9%).The proportion of kitchens in the living room for women exposed to cooking biofuels was 4.7%(95%CI:2.4%?7.0%),which was significantly higher for the unexposed women(2.9%)(?2=5.67,P=0.0173).The proportion of kitchens in the living room for women exposed to cooking coal was 12.9%(95%CI:5.7%?20.1%),significantly higher than that of women unexposed to cooking coal(2,2%,95%CI:1.6%?2.8%)(?2=89.98,P<0.0001).??The association between biomass exposure and chronic obstructive pulmonary disease among Chinese women aged 40 or older1.Prevalence of COPD among populations with different characteristicsA total of 34 623 women completing the bronchial dilatation test.The effective samples analyzed in this section were 33 615 women who passed the diastolic pulmonary function tests.There were 2 499 patients with COPD,and the overall prevalence of COPD was 8.1%(95%CI:6.8%-9.3%).The study showed that the prevalence of COPD increased with the increment of age,with a prevalence of 14.5%in the ?60 age group.The prevalence of COPD was significantly higher in primary and lower education(10.0%)than that in junior high school and above(5.7%)(P<0.0001).The prevalence of COPD in women who hospitalized with a history of severe lung disease was significantly higher than those without hospitalization(16.4%vs.7.9%,P<0.0001).The COPD prevalence of those with a history of pulmonary tuberculosis were higher than those with no history of tuberculosis(17.6%vs.8.0%,P<0.0001).Those with family history of respiratory disease were higher than those without family history of respiratory disease(11.7%vs.7.2%,P<0.0001).The prevalence of COPD in low body mass index(14.5%)was significantly higher than that in normal body weight(8.2%)and overweight and obese(7.7%)(P<0.0001).The prevalence of COPD among smokers was significantly higher than that of never smokers(16.2%vs.7.6%,P<0.0001).The prevalence of COPD in those exposed to cooking biofuels was 9.8%higher than those without exposure(7.2%)(P=0.0139).However,the prevalence of COPD between urban women and rural women,exposed and unexposed workers with occupational dust and/or harmful gases,with/without passive smokers,exposed and unexploited people exposed to cooking coal,and people with different heating methods Statistical differences.2.Multivariate Logistic Regression Analysis of the Risk Factors of COPDAfter adjusting for confounding factors,the risk of COPD increased with age,and the risk of COPD of women aged 60 or older was higher than those aged 40 to 49(OR=3.46,95%CI:2.88?4.16).The OR of the COPD patients with severe lung disease during childhood was 2.50(95%CI:1.97?3.17).The OR of patients with a history of pulmonary tuberculosis was 1.86(95%CI:1.41?2.46).The OR of patients with family history of respiratory disease was 1.80(95%CI:1.61?2.02).Low body weight was a risk factor for COPD compared with normal weight(OR=1.56,95%CI:1.24-1.94).The risk of COPD in women with smoking increased significantly(OR=2.07,95%CI:1.69-2.53).Multivariate analysis showed occupational exposure to dust and/or harmful gases(OR=1.02,95%CI:0.88?1.18),passive smoking(OR=0.95,95%CI:0.85?1.06),and exposure to cooking coal(OR=0.91,95%CI;0.72?1.15)did not increase the risk of COPD in women 40 years of age or older(P>0.05).The exposure of cooking biomass increased the risk of COPD by 15%(OR=1.15,95%CI:0.93?1.42,P=0.2002)compared to those unexposed to cooking biomass.The use of coal warmers increased the risk of COPD by 12%compared to those who did not use heating/cleaning(OR=1.12,95%CI:0.93?1.35,P=0.2266).3.Logistic analysis of the relationship between biomass exposure and COPDUnivariate Logistic analysis showed that the risk of COPD of women exposed to cooking biomass was 1.35 times that of non-exposed individuals(OR=1.35,95%CI:1.11?1.65,P=0.0028).After adjusting for age,the OR was 1.28(95%CI:1.05?1.56,P=0.0163).After adjusting for age and smoking factors,the OR was 1.27(95%CI:1.04?1.55,P=0.0204).After further adjustment of age,smoking,childhood hospitalization due to severe pulmonary disease,history of tuberculosis,history of family respiratory disease,exposure to occupational dust and/or harmful gases,passive smoking,BMI,winter heating patterns,exposure to cooking coal,the OR was 1.26(95%CI:1.03-1.54,P=0.0266).4.The Relationship between Biomass Exposure and COPD after Urban-rural StratificationAmong the urban female,the prevalence of COPD in exposed biofuels(8.9%%)was higher than that in non-exposed individuals(7.3%)(P=0.2703).In rural women,the prevalence of COPD in exposed biofuels(10.1%)was higher than those in unexposed individuals(7.0%)(P=0.0448).Adjusted for age,smoking,childhood hospitalization due to severe pulmonary disease,history of pulmonary tuberculosis,history of family respiratory disease,exposure to occupational dust and/or harmful gases,passive smoking,BMI,winter heating patterns,factors of exposure to cooking coal,the risk of COPD of urban women exposed to cooking biomass was 1.20 times that of non-exposed urban individuals(OR=1.20,95%CI:0.89?1.61).The prevalence of COPD was higher in rural women exposed to cooking biofuels(9.1%)than in those non-exposed(6.5%)(P=0.0066),the OR was 1.25(95%CI:0.97?1.62)after controlling other factors,closed to statistically significant(P=0.0828).5.Population Attributable Risk Percent of biomass exposure to female COPD(PAR%)The PAR%of cooking biomass exposure to female COPD was 8.4%.After urban and rural stratification,the PAR%of cooking biomass exposure to urban COPD was 3.5%,much lower than that of rural COPD(11.3%).Conclusion1.The prevalence of biomass exposure is high in Chinese women aged 40 years or older,and with differences found between different regions,especially in rural areas where biomass exposure is more serious.2.The prevalence of COPD in Chinese women aged 40 years or older is as high as 8.1%.3.Exposure to cooking biomass increases the risk of COPD among women,and is a risk factor for COPD.4.The PAR%for female COPD in cooking biomass is higher,especially for women in rural areas.And enough attention should be paid to the biomass exposure.