Objective To investigate the smoking status and factors influencing tobacco dependence among inpatients with respiratory diseases, and analyze the relationship of salivary and plasma nicotine metabolic ratio (NMR) with tobacco dependence and withdrawal symptoms. Methods A cross-sectional study was conducted on eligible patients admitted to the Department of Respiratory and Critical Care Medicine, West China Hospital of Sichuan University, between October 2023 and October 2024. Basic information of enrolled patients was collected and smoking questionnaires were administered. The participants were categorized into current smokers or former smokers based on smoking status. The current smokers were classified into no dependence, mild dependence, moderate dependence, and severe dependence by ICD-10, Chinese guidelines, and FTND. Group differences were analyzed with ANOVA and chi-square test. Tobacco dependence risk factors were identified by univariate/multivariate logistic regression. The smokers were stratified into slow and normal metabolizers based on NMR to analyze its correlation with tobacco dependence and withdrawal symptoms. Results Among 602 enrolled patients, 20.4% initiated smoking before age 18 years, with a mean smoking history of 46.2 pack-years. Family members smoked in 49.3% and friends smoked in 89.5% of cases; primary smoking motivations were conformity, curiosity, and boredom relief. Tobacco dependents had significantly higher rates of family member smoking (P=0.005) and withdrawal symptoms (P<0.001). Logistic regression identified lower education level, absence of pulmonary infection, parental smoking, and higher daily cigarette consumption as significant risk factors for tobacco dependence. NMR was positively correlated with nicotine dependence severity (saliva: rs=0.303, P=0.013; plasma: rs=0.297, P=0.045). Normal metabolizers had a significantly higher prevalence of nicotine dependence than slow metabolizers (saliva: 56.3% vs. 33.3%, P=0.014; plasma: 58.8% vs. 25.0%, P=0.044). Withdrawal symptoms were positively correlated with NMR (rs=0.244, P=0.048), with a higher incidence in normal metabolizers (81.3% vs. 58.8%, P=0.048). Conclusions Lower education level, absence of pulmonary infection, parental smoking, and higher daily cigarette consumption are major risk factors for tobacco dependence. Normal nicotine metabolizers are more likely to exhibit higher levels of tobacco dependence and withdrawal symptoms than slow metabolizers.
