The association between nonalcoholic fatty liver disease and metabolic comorbidities

Potential conflict of interest: Nothing to report. To the Editor: We read with great interest the research by Allen et al.1 They investigated the trends in nonalcoholic fatty liver disease (NAFLD) incidence and the impact of NAFLD on incident metabolic comorbidities, cardiovascular events, and mortality from a community cohort of all adults diagnosed with NAFLD in Olmsted County during 1997‐2014 using the Rochester Epidemiology Project database. However, there are some key points worthy of discussion. Firstly, the current study examined the temporal associations between rates of NAFLD and the frequency of abdominal ultrasound testing in all Olmsted County residents during the study time frame. Abdominal B‐mode ultrasonography may underestimate the true prevalence of NAFLD as ultrasound examinations of the liver are relatively insensitive in cases where the hepatic lipid content is <30%.2 Therefore, to enhance the diagnosis rate of NAFLD, laboratory tests and FibroScan examinations should be included, and liver biopsies should be performed when necessary. Secondly, in this context, the NAFLD incidence increase was highest (7‐fold) in young adults, aged 18‐39 years; and the steeper increase in NAFLD diagnosis in young adults compared to other age groups is alarming. In addition, studies have revealed that NAFLD is currently the most common liver abnormality in children aged 2‐19 years, with a prevalence as high as 38% in obese children.3 Because this study is only focused on the incidence of NAFLD in adults, the incidence of NAFLD in children and teenagers was not investigated. Thirdly, this study reported that the prevalence of obesity among NAFLD subjects remained constant at 68% during the study period. Interestingly, studies4 have indicated that 7.6%‐25.6% of NAFLD patients have a normal body mass index, and their condition is known as "nonobese NAFLD," which is consistent with the proportion of nonobese NAFLD patients in this study (approximately 32%). Therefore, the absence of obesity and weight gain that has not yet resulted in obesity (especially in individuals aged 20 years and older) are also key predictive factors in the onset of NAFLD and the subsequent induction of metabolic syndrome. Therefore, segregation of the patient population for discussion in this study is recommended.