Letter: hereditary role in non‐alcoholic fatty liver disease

Editors, In their recent nationwide cohort study, Park et al analysed datasets from the Korean National Health and Nutrition Examination Surveys and evaluated the risk of nonalcoholic fatty liver disease (NAFLD) between parents and their children between 12 and 18 years old.1 Detailed nutritional intake and laboratory data were recorded in the database and were considered covariates in the analyses. In previous studies, the influence of NAFLD on offspring has been widely discussed; possible aspects including genetic and epigenetic issues could be involved.2 The robust database used in the current study could therefore make the reported results more convincing and could serve as useful realworld evidence of a hereditary role in NAFLD pathogenesis. However, we would like to raise some issues about the potential influence that NAFLD riskassociated comorbidities could cause and the issue regarding body mass index (BMI) adjustment. The influence of comorbidities should not be overlooked, since these points could possibly influence the interpretation of the results. In the current study, the presence of NAFLD highrisk comorbidities was not set as covariate, which could potentially lead to confounding bias. In previous studies, inflammatory diseases such as psoriasis and inflammatory bowel disease were associated with a higher risk of NAFLD.3,4 Likewise, the presence of diabetes mellitus was also a critical confounder, for it was considered one of the most significant risk factors of NAFLD.5 Given that the distribution of underlying comorbidities was not available in the baseline characteristics, we were unable to determine whether the presence of inflammatory comorbidities and diabetes would influence the outcome evaluation. Another issue regards the adjustment of BMI. The authors stated that BMI was considered one of the variables and was adjusted in specific models. We were extremely interested in the adjustment of BMI. Was the adjustment based on the value of children's, maternal or parental BMI? This seemed unclear since the authors did not explain it in detail. A recent report indicated that maternal prepregnancy BMI could influence the occurrence of NAFLD in offspring.6 In this case, if the adjustment only included children's BMI, there is potential for bias.