Prevalence of physician-diagnosed COPD and its association with smoking among urban and rural residents in regional mainland China

Objectives: To investigate the prevalence of physician-diagnosed COPD and to explore the relationship between the total amount of cigarettes smoked (TACS) and COPD among urban and rural adults in Nanjing, China. Design: Population-based, cross-sectional study conducted between October 2000 and March 2001. Setting: Administrative villages (n = 45) randomly selected from three urban districts and two rural counties of Nanjing municipality, Jiangsu province, China, with an overall population of 5.6 million. Participants: All regular local residents >= 35 years old (n = 29,319), 67.7% from urban areas and 32.3% from rural areas; 49.7% were men and 50.3% were women. Results: The response rate of potential participants was 90.1%. The overall prevalence of diagnosed COPD was 5.9%. The prevalence of COPD was significantly higher among men than in women (7.2% vs 4.7%, p = 0.000), while the difference between urban and rural participants was not statistically significant (6.7% vs 4.4%, respectively; p = 0.132). The prevalence of COPD was significantly higher among smokers than nonsmokers. After adjusting for age, gender, area of residence, fuels, heating in winter, ventilation in kitchen, passive smoking, education, occupation, average family income, alcohol drinking, cooking oil, body mass index, and physical activity, a dose-response relationship between COPD and TACS was evident in this population (odds ratio [OR], 1.60; 95% confidence interval [CI], 1.34 to 1.92; OR, 1.39; 95% Cl, 1.13 to 1.70; and OR, 1.24; 95% C1, 1.01 to 1.52 for smokers within upper, middle, and lower TACS levels compared with nonsmokers, respectively). Conclusions: The overall prevalence of diagnosed COPD (5.9%) among Chinese adults was higher than that (2.5%) estimated by World Health Organization experts, and there was a significant gradient increase in COPD prevalence from the stratum of nonsmokers to the stratum of upper TACS.