Association of active and passive smoking with noncommunicable diseases in a large health check-up population: A cross-sectional study in Changzhi, Shanxi province, China.

INTRODUCTION: Tobacco smoke, encompassing both active smoking and secondhand smoke (SHS) exposure, constitutes a leading modifiable risk factor for the global burden of non-communicable diseases (NCDs). This study aimed to examine the association of active smoking and SHS with the presence of NCDs among health check-up populations, and to explore the dose-response association according to daily cigarette consumption and smoking duration. METHODS: A cross-sectional study was conducted among 38906 adults aged ≥18 years who were local residents undergoing physical examination in Changzhi, Shanxi Province from January to December 2025. Questionnaire interviews were used to capture the demographics, lifestyle habits, tobacco smoke status (active smoking, SHS exposure, daily cigarette consumption, and smoking duration), and clinically diagnosed NCDs. Multivariable logistic regression estimated the adjusted odds ratios (AORs) and 95% confidence intervals (CIs), with adjustment for potential confounders. In this study, a p<0.05 was considered statistically significant. RESULTS: The overall prevalence of current smoking was 27.3% (51.3% in men, 0.3% in women), and 26.2% of participants had at least one NCD. After full adjustment, active smoking remained independently associated with increased odds of NCDs (AOR=1.26; 95% CI: 1.18-1.35). A modest dose-response gradient was observed for smoking duration: compared with <5 years, the AORs were 1.24 (95% CI: 1.08-1.43) for 5-14 years, 1.23 (95% CI: 1.09-1.39) for 15-24 years, and 1.37 (95% CI: 1.19-1.58) for ≥25 years. Daily consumption of ≥20 cigarettes was modestly associated with elevated risk (AOR=1.13; 95% CI: 1.03- 1.25). Regarding SHS, the crude association was significant (OR=1.25; 95% CI: 1.16-1.35), but attenuated after adjusting for potential confounders (AOR=1.04; 95% CI: 0.95-1.13). In subgroup analyses, active smoking was associated with hypertension, diabetes, cardiovascular disease and dyslipidemia, and the doseresponse relationships were also observed for smoking duration. CONCLUSIONS: Active smoking independently increases the odds of prevalent NCDs, especially among long-term smokers. The attenuated effect of SHS highlights the challenge of isolating its independent role in observational settings. So comprehensive tobacco control strategies and targeted cessation interventions for long-term smokers are important.