Prevalence of respiratory diseases in relation to smoking rate in adults living in four Chinese cities: a comparison between 2017–2018 and 1993–1996

BACKGROUND: The sustained high prevalence of smoking in China has contributed substantially to the burden of chronic diseases, including respiratory diseases. This study compared the prevalence of smoking and respiratory diseases in Chinese adults between two time periods spanning over 25 years. METHODS: Cross-sectional surveys were performed in four Chinese cities of Chongqing, Lanzhou, Wuhan, and Guangzhou in 1993–1996 (Period 1) and in 2017–2018 (Period 2). Participants completed questionnaires asking smoking status, the presence of asthma and chronic bronchitis, education attainment and household characteristics. Logistic regression models were used to estimate the odds ratios of disease prevalence with regard to active smoking status for men and passive smoking status for women. RESULTS: Prevalence of asthma, prevalence of chronic bronchitis, and smoking rate, all decreased from Period 1 to Period 2. We observed strong evidence that active smoking increased prevalence for both asthma and chronic bronchitis in men during Period 1, with spatial heterogeneity and modifying effect by college-level education. Home exposure to passive smoking was associated with increased odds of having chronic bronchitis among female participants in Chongqing during Period 2, although the association was not statistically significant. CONCLUSIONS: The prevalence for asthma and chronic bronchitis were lower in 2017–2018 compared to 25 years ago in the same four Chinese cities. Decreased smoking rate may have contribution to the improvement of these respiratory diseases. Male smokers, especially those without college-level education, showed higher prevalence of chronic bronchitis compared to nonsmokers during Period 1.