Associations Between Active,Passive Smoking and the Risk of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease(NAFLD)is the most common chronic liver disease with an estimated worldwide prevalence of 32.4%.1 The multisystem condition is related to an increased risk of liver-related and cardiovascular extrahepatic diseases.2 Smoking is the leading preventable risk factor for premature disability and mortality.As NAFLD and smoking are both associated with the development of metabolic features,there has been increasing interest in testing the relationship between smoking and NAFLD.The causal relevance of smoking to NAFLD incidence have been implicated in crosssectional and prospective cohort studies.3,4 However,previous studies mainly focused on the effect of active smoking,discussion on the influence of passive smoking on NAFLD will facilitate illustrating the association between smoking and NAFLD.We conducted a national two-center cross-section study of active,passive smoking and NAFLD risk in Chinese and European population.This design allowed us to(1)test for associations between active,passive smoking and NAFLD risk by sex and consolidate evidence for causality by estimating dose-response relationship,(2)identify mediated factors,and(3)resolve their possible interaction with smoking.