title: COPD and its association with smoking in the Mainland China: a cross-sectional analysis of 0.5 million men and women from ten diverse areas.
abstract: OBJECTIVE
  In adult Chinese men, smoking prevalence is high, but little is known about its association with chronic respiratory disease, which is still poorly diagnosed and managed.
  
  
  METHODS
  A nationwide study recruited 0.5 million men and women aged 30-79 years during 2004-2008 from ten geographically diverse areas across the Mainland China. Information was collected from each participant regarding smoking and self-reported physician diagnosis of chronic bronchitis/emphysema (CB/E), along with measurement of lung function indices. Logistic regression was used to yield sex-specific odds ratios (ORs) relating smoking to airflow obstruction (AFO), defined as forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) <0.7 and CB/E, adjusting for age, areas, education, and income.
  
  
  RESULTS
  Overall 74% of men were ever regular smokers; among them, 7.2% had AFO compared with 5.4% in never-smokers, yielding an OR of 1.42 (95% confidence interval [CI]: 1.34-1.50). The risk was strongly associated with amount smoked and starting to smoke at a younger age. Among ex-smokers, the OR was more extreme for those who had quit due to illness (OR: 1.86, 95% CI: 1.77-1.96) than those who had quit by choice (OR:1.08, 95% CI: 1.01-1.16). CB/E prevalence was also significantly elevated in ex-smokers who had quit because of ill health (OR:2.79, 95% CI: 2.64-2.95), but not in regular smokers (OR:1.04, 95% CI: 0.96-1.11). Female smokers was rare (3%), but carried an excess risk for AFO (OR:1.53, 95% CI: 1.43-1.65) and, to a lesser extent, for CB/E (OR:1.28, 95% CI: 1.15-1.42).
  
  
  CONCLUSIONS
  In Mainland China, adult smokers, particularly ex-smokers who had quit because of illness, had significantly higher prevalence of chronic respiratory disease. AFO appeared to be more strongly associated with smoking than self-reported chronic respiratory disease.
authors.affiliation: Nuffield Department of Population Health, Clinical Trial Service Unit and Epidemiological Studies Unit (CTSU), University of Oxford, Oxford, UK.
authors.forename: Om P
authors.initials: OP
authors.lastname: Kurmi
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, Mainland China ; Chinese Academy of Medical Sciences, Dong Cheng District, Beijing, Mainland China.
authors.forename: Liming
authors.initials: L
authors.lastname: Li
authors.affiliation: Nuffield Department of Population Health, Clinical Trial Service Unit and Epidemiological Studies Unit (CTSU), University of Oxford, Oxford, UK.
authors.forename: Jenny
authors.initials: J
authors.lastname: Wang
authors.affiliation: Nuffield Department of Population Health, Clinical Trial Service Unit and Epidemiological Studies Unit (CTSU), University of Oxford, Oxford, UK.
authors.forename: Iona Y
authors.initials: IY
authors.lastname: Millwood
authors.affiliation: China National Center for Food Safety Risk Assessment, Beijing, Mainland China.
authors.forename: Junshi
authors.initials: J
authors.lastname: Chen
authors.affiliation: Nuffield Department of Population Health, Clinical Trial Service Unit and Epidemiological Studies Unit (CTSU), University of Oxford, Oxford, UK.
authors.forename: Rory
authors.initials: R
authors.lastname: Collins
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, Mainland China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, Mainland China.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Bian
authors.affiliation: NCDs Prevention and Control Department, Huixian CDC, Huixian, Henan, Mainland China.
authors.forename: Jiangtao
authors.initials: J
authors.lastname: Li
authors.affiliation: NCDs Prevention and Control Department, Hunan CDC, Changsha, Mainland China.
authors.forename: Biyun
authors.initials: B
authors.lastname: Chen
authors.affiliation: NCDs Prevention and Control Department, Tongxiang CDC, Zhejiang, Mainland China.
authors.forename: Kaixu
authors.initials: K
authors.lastname: Xie
authors.affiliation: NCDs Prevention and Control Department, Liuyang CDC, Baiyikengdao, Liuyang, Changsha, Hunan, Mainland China.
authors.forename: Weifan
authors.initials: W
authors.lastname: Jia
authors.affiliation: NCDs Prevention and Control Department, Sichuan CDC, Sichuan, Mainland China.
authors.forename: Yali
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Nuffield Department of Population Health, Clinical Trial Service Unit and Epidemiological Studies Unit (CTSU), University of Oxford, Oxford, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Peto
authors.affiliation: Nuffield Department of Population Health, Clinical Trial Service Unit and Epidemiological Studies Unit (CTSU), University of Oxford, Oxford, UK.
authors.forename: Zhengming
authors.initials: Z
authors.lastname: Chen
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D005541:Forced Expiratory Volume; D006306:Health Surveys; D006801:Humans; D016015:Logistic Models; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D015995:Prevalence; D065840:Protective Factors; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology; D018570:Risk Assessment; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology* / Q000503:physiopathology; D016540:Smoking Cessation; D000074606:Smoking Prevention; D013997:Time Factors; D014797:Vital Capacity
keywords: China Kadoorie Biobank; Mainland China; airflow obstruction; chronic respiratory diseases; smoking cessation
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