Clinical course of non-alcoholic fatty liver disease and the implications for clinical trial design

Background & Aims: The predicted risk and timeline to progression to liver-related outcomes in the population with NAFLD are not well-characterized. We aimed to examine the risk and time to progression to cirrhosis, hepatic decompensation and death in a contemporary population over a long follow-up period, to obtain information to guide endpoint selection and sample size calculations for clinical trials on NAFLD-related cirrhosis. Methods: This is a retrospective study of prospectively collected data in a medical record linkage system, including all adults diagnosed with NAFLD between 1996-2016 by clinical, biochemical and radiological criteria in Olmsted County, Minnesota and followed until 2019. Liver-related outcomes and death were ascertained and validated by individual medical record review. Time and risk of progression from NAFLD to cirrhosis to decompensation and death were assessed using multistate modeling. Results: A total of 5,123 individuals with NAFLD (median age 52 years, 53% women) were followed for a median of 6.4 (range 1-23) years. The risk of progression was as follows: from NAFLD to cirrhosis: 3% in 15 years; compensated cirrhosis to first decompensation: 33% in 4 years (8%/year); first decompensation to ≥2 decompensations: 48% in 2 years. Albumin, bilirubin, non-bleeding esophageal varices and diabetes were independent predictors of decompensation. Among the 575 deaths, 6% were liver related. Therapeutic trials in compensated cirrhosis would require enrolment of a minimum of 2,886 individuals followed for >2 years to detect at least a 15% relative decrease in liver-related endpoints. Conclusion: In this population-based cohort with 23 years of longitudinal follow-up, NAFLD was slowly progressive, with liver-related outcomes affecting only a small proportion of people. Large sample sizes and long follow-up are required to detect reductions in liver-related endpoints in clinical trials. Lay summary: For patients with compensated non-alcoholic steatohepatitis-related cirrhosis, the time spent in this state and the risk of progression to decompensation are not well-known in the population. We examined the clinical course of a large population-based cohort over 23 years of follow-up. We identified that adults with compensated cirrhosis spend a mean time of 4 years in this state and have a 10% per year risk of progression to decompensation or death. The risk of further progression is 3-fold higher in adults with cirrhosis and one decompensating event. These results are reflective of placebo arm risks in drug clinical trials and are essential in the estimation of adequate sample sizes.