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Background and aimsLarge prospective studies to establish the prevalence of nonalcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH), are lacking. We prospectively assessed the prevalence and severity of NAFLD/NASH in a cohort of asymptomatic middle-aged Americans attending a colonoscopy class at a gastroenterology clinic.MethodsScreening for NAFLD was performed using magnetic resonance (MR)-based LiverMultiScan® proton density fat fraction (LMS-PDFF). MR exams also included corrected T1 and elastography for liver stiffness measurement (LSM). FibroScan® was also used to measure LSM. Participants with predetermined abnormal imaging parameters were proposed a liver biopsy to evaluate for NASH. Biopsies were read in a blinded fashion with consensus by two expert pathologists. The prevalence of NAFLD was determined by PDFF ≥ 5% or when PDFF and biopsy data available, by histological diagnosis of NAFLD. The prevalence of NASH was defined by biopsy.ResultsOf 835 participants, 664 subjects met the inclusion and exclusion criteria. The mean age was 56 ± 6.4 years, 50% were male, the mean body mass index was 30.48 ± 5.46 kg/m2, and 52% were obese. The prevalence of NAFLD was 38% (95% CI 34-41%) and the prevalence of NASH was 14% (95% CI 12-17%). While no patient had cirrhosis on biopsy, significant fibrosis (F ≥ 2) was present in 5.9% (95% CI: 4-8%) and bridging fibrosis in 1.6% (95% CI: 1-3%). In a multivariable analysis, factors associated with the presence of NASH were race, obesity, and diabetes.ConclusionUsing state-of-the-art liver imaging modalities and reference biopsy, this study establishes an overall prevalence of NAFLD of 38% and NASH by biopsy of 14% in this cohort of asymptomatic middle-aged US adults. Lay summary.

Original publication




Journal article


Journal of hepatology

Publication Date



Radcliffe Department of Medicine, University of Oxford, UK. Electronic address: