[Association of solid fuel use for heating and smoking with respiratory diseases: a prospective cohort study].

Objective: To investigate the association between solid fuel use for heating, smoking, and respiratory diseases. Methods: This study is based on the Qingdao project of the China Kadoorie Biobank. After screening, 26 165 individuals were included in the study. We employed Cox proportional hazards regression models, stratified by risk age (in 5-year intervals) and sex while adjusting for confounding variables such as occupation and physical activity level to analyze the association between solid fuel use for heating, smoking, and increased risk of respiratory diseases. Results: Among the 26 165 participants, the average age of those using solid fuel for heating was (52.57±10.31) years, with females constituting 58.04% and former/current smokers accounting for 65.38%. The results indicated that both the solid fuel group and the former/current smoking group had a higher risk of respiratory diseases, with hazard ratios (HR) (95%CI) of 1.21 (1.04-1.41) and 1.41 (1.16-1.71), respectively. For the duration of solid fuel use, the HR (95%CI) for 20 years or more, it was 1.27 (1.07-1.51). The multiplicative interaction term between solid fuel use and smoking was statistically significant. Conclusions: The use of solid fuel for heating and smoking significantly increases the risk of respiratory diseases, and there may be a multiplicative interaction between solid fuel use and smoking.