Associations of light smoking with serum carcinoembryonic antigen and relative leukocyte telomere length in men with asthma.

Smoking and asthma are associated with oxidative stress and chronic inflammation, which may contribute to accelerated cellular aging. Relative leukocyte telomere length (RTL) and serum carcinoembryonic antigen (CEA) are accessible biomarkers linked to these pathways, but their associations with light smoking (1-4 cigarettes/day) in men with asthma remain unclear. This cross-sectional study included 156 men: 73 with asthma and 83 healthy controls, classified as asthmatic light smokers, asthmatic nonsmokers, healthy light smokers, or healthy nonsmokers. Primary analyses used outcome-specific datasets after within-group Tukey 1.5×IQR exclusion, yielding 150 observations for CEA and 148 for RTL; complete-data and age-restricted analyses were sensitivity analyses. CEA differed across groups and was higher in asthmatic light smokers than in healthy nonsmokers (Dunn-Bonferroni p=0.006). In the age-adjusted full-cohort model, light smoking among participants with asthma was associated with higher CEA [adjusted ratio 1.18, 95% confidence interval (CI) 1.01-1.38; p=0.034]. This association became statistically inconclusive after broader adjustment. RTL also differed across groups and was shorter in asthmatic light smokers than in asthmatic nonsmokers (Dunnett T3 p=0.001). In the primary median-regression model, light smoking among participants with asthma was associated with lower RTL (adjusted conditional-median ratio 0.38, 95% bootstrap CI 0.22-0.67; p=0.001), but this association was not consistently retained in severity-adjusted, complete-data, and age-restricted analyses. Asthma-status×smoking-status interactions were nonsignificant for both biomarkers. Light smoking was associated with higher CEA and lower RTL in the primary models, but both findings were sensitive to analytical specification. These exploratory cross-sectional associations do not establish causality and require longitudinal confirmation.