Prospective evaluation of the prevalence of non-alcoholic fatty liver disease and steatohepatitis in a large middle-aged US cohort.

BACKGROUND AND AIMS: Large 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.

METHODS: Screening 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.

RESULTS: Of 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.

CONCLUSION: Using 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.