The prevalence of and risk factors for non-smoking chronic obstructive pulmonary disease in China: A systematic review and meta-analysis

Background: In China, chronic obstructive pulmonary disease (COPD) is one of the most common chronic diseases. The prevalence of and risk factors for non-smoker COPD in China remains to be known. Objectives: To estimate the proportion of non-smokers in COPD patients and to evaluate the risk factors for COPD in non-smokers in China. Data sources Six databases from inception to 1st May 2022 were searched. Results: Overall, 95 studies with a total of 482,158 participants were included. The percentage of never-smokers among people with COPD was 42% (95% CI: 38% to 45%, P < 0.001). The proportion of never-smokers in males with COPD was 22% (95% CI: 19% to 26%, P < 0.001), which was different from that in females (81%, 95% CI: 75% to 87%, P < 0.001). The results showed an association between biomass fuel and COPD in never-smokers (OR: 1.25, 95% CI: 1.06 to 1.44). Data from four studies showed a close association between underweight and COPD in never-smokers (OR: 1.89, 95% CI 1.78 to 2.00). An association between history of tuberculosis and COPD was also observed in never-smokers (OR: 1.71, 95% CI 1.53 to 1.88). No associations were identified for passive smoking and COPD in never-smokers (OR: 0.90, 95% CI 0.87 to 0.94). Interestingly, data from three studies showed being male gender was associated with a risk for COPD in nonsmokers (OR: 1.36, 95% CI 1.22 to 1.51). Never-smokers living in rural areas or those with low educational status were more susceptible to COPD. Conclusions: This review confirmed the highly different proportions of never-smokers in male and female COPD patients. Biomass fuel might have important roles in the risk for COPD among never-smokers.