Association between serum cotinine level and prevalence of non-alcoholic fatty liver disease: a cross-sectional study from the Third National Health and Nutrition Examination Survey.

The data on the effect of smoking on non-alcoholic fatty liver disease (NAFLD) has been controversial. The aim of this study was to investigate if an association exists between serum cotinine level (a tobacco biomarker) and NAFLD prevalence in the general US population. We conducted a cross-sectional analysis of data from the Third National Health and Nutrition Examination Survey (NHANES III). We included 11,003 adults aged 20-74 years who underwent ultrasonography. Of those, 4036 were identified as having NAFLD and 6967 were recognized as controls. The percentage of current smokers was significantly lower in subjects with NAFLD compared with those in controls (21.5% vs 26.0%, p<0.01). After adjustment for potential confounders, there was no association between current or former smokers with NAFLD. Additionally, no associations were observed between the levels of serum cotinine and NAFLD. No association between serum cotinine levels at each quartile level and NAFLD was observed regardless of smoking status. In this large US population-based study, we did not find an association between NAFLD and self-reported smoking status or measured serum cotinine level.