Association between cotinine‐verified smoking status and risk of nonalcoholic fatty liver disease

Abstract Background & Aims The relationship between cigarette smoking and nonalcoholic fatty liver disease ( NAFLD ) has been controversial. Most relevant studies have relied on self‐reported questionnaires. We aimed to elucidate the association between smoking status and NAFLD using an objective biomarker of tobacco exposure (urinary cotinine) and self‐reported questionnaire. Methods A cross‐sectional study was conducted on 160 862 asymptomatic examinees who underwent abdominal ultrasonography and urinary cotinine measurements between April 2011 and December 2015. Cotinine‐verified current smokers were defined as participants with urinary cotinine levels ≥50 ng/ mL . Results The mean age of the study population was 36.1 years, and the proportion of men was 51.7%. The proportions of self‐reported and cotinine‐verified current smokers were 17.6% and 17.7% respectively. After adjusting for confounding factors, self‐reported current smoking was associated with an increased risk of NAFLD (adjusted odds ratio [ AOR ], 1.10; 95% confidence interval [ CI ], 1.06‐1.14). Moreover, among the current smokers, the risk of NAFLD increased with an increase in the amount of cigarette smoking (<10 and ≥10 pack‐years vs never smokers; AOR , 1.04 and 1.11; 95% CI , 1.01‐1.08 and 1.05‐1.16 respectively). Cotinine‐verified current smoking was also associated with an increased risk of NAFLD ( AOR , 1.10; 95% CI , 1.06‐1.14). Conclusions Cotinine‐verified current smoking and self‐reported current smoking were independent risk factors for NAFLD . Further longitudinal studies are needed to more clearly elucidate the impact of smoking on the development of NAFLD .