Progression of non-alcoholic fatty liver disease and long-term outcomes: A nationwide paired liver biopsy cohort study

•In adults with NAFLD and paired clinical liver biopsies, a substantial proportion experienced progression between biopsies. •NAFLD progression was associated with a markedly higher incidence of end-stage liver disease. •In contrast, NAFLD progression was not associated with significantly worse overall mortality. Background & Aims More data are needed regarding the long-term impact of the histological progression of non-alcoholic fatty liver disease (NAFLD) on long-term outcomes, including end-stage liver disease (ESLD) and mortality. Methods We included Swedish adults with biopsy-confirmed non-cirrhotic NAFLD and ≥2 liver biopsies >6 months apart (1969-2017; n = 718). NAFLD was categorized at initial biopsy as simple steatosis, non-fibrotic steatohepatitis (NASH), or non-cirrhotic fibrosis. NAFLD progression was defined by histological changes between biopsies (i.e. incident NASH, incident fibrosis, fibrosis progression, cirrhosis). Using Cox regression, we estimated multivariable adjusted hazard ratios (aHRs) and 95% CIs for incident ESLD (i.e. hospitalization for decompensated cirrhosis, hepatocellular carcinoma or liver transplantation) and mortality, according to NAFLD progression vs. stable/regressed disease. Results At initial biopsy, 497 patients (69.2%) had simple steatosis, 90 (12.5%) had non-fibrotic NASH, and 131 (18.2%) had non-cirrhotic fibrosis. Over a median of 3.4 years between biopsies, 30.4% (218/718) experienced NAFLD progression, including 12.5% (62/497) with incident non-fibrotic NASH, 24.0% (141/587) with incident fibrosis, and 5.6% (40/718) with cirrhosis. Compared to stable/regressed disease, NAFLD progression was associated with significantly higher rates of developing incident ESLD (23.8 vs. 11.4/1,000 person-years [PY]; difference = 12.4/1,000 PY; aHR 1.65, 95% CI 1.17-2.32). While the highest ESLD incidence occurred with progression to cirrhosis (difference vs. stable/regressed disease = 56.3/1,000 PY), significant excess risk was also found with earlier transitions, including from simple steatosis to incident fibrosis (difference vs. stable/regressed disease = 18.9/1,000 PY). In contrast, all-cause mortality rates did not appear to differ when NAFLD progression was compared to stable/regressed disease (difference = 4.7/1,000 PY; aHR 0.99, 95% CI 0.78-1.24). Conclusions In a nationwide, real-world cohort of patients with paired NAFLD biopsies, histological disease progression contributed to significantly higher rates of developing incident ESLD, but did not appear to impact all-cause mortality. Impact and implications Currently, data are scarce regarding the long-term impact of histological progression or regression of non-alcoholic fatty liver disease (NAFLD) on subsequent risk of adverse clinical outcomes, including the development of end-stage liver disease and mortality. This is particularly important because randomized-controlled trials of NAFLD therapeutics currently focus on short-term histological endpoints as presumed surrogates for those major clinical outcomes. Thus, the results from this study can help inform the optimal design of future NAFLD therapeutic trials, while also providing the necessary evidence base for public health policies focused on preventing the development and progression of NAFLD. More data are needed regarding the long-term impact of the histological progression of non-alcoholic fatty liver disease (NAFLD) on long-term outcomes, including end-stage liver disease (ESLD) and mortality. We included Swedish adults with biopsy-confirmed non-cirrhotic NAFLD and ≥2 liver biopsies >6 months apart (1969-2017; n = 718). NAFLD was categorized at initial biopsy as simple steatosis, non-fibrotic steatohepatitis (NASH), or non-cirrhotic fibrosis. NAFLD progression was defined by histological changes between biopsies (i.e. incident NASH, incident fibrosis, fibrosis progression, cirrhosis). Using Cox regression, we estimated multivariable adjusted hazard ratios (aHRs) and 95% CIs for incident ESLD (i.e. hospitalization for decompensated cirrhosis, hepatocellular carcinoma or liver transplantation) and mortality, according to NAFLD progression vs. stable/regressed disease. At initial biopsy, 497 patients (69.2%) had simple steatosis, 90 (12.5%) had non-fibrotic NASH, and 131 (18.2%) had non-cirrhotic fibrosis. Over a median of 3.4 years between biopsies, 30.4% (218/718) experienced NAFLD progression, including 12.5% (62/497) with incident non-fibrotic NASH, 24.0% (141/587) with incident fibrosis, and 5.6% (40/718) with cirrhosis. Compared to stable/regressed disease, NAFLD progression was associated with significantly higher rates of developing incident ESLD (23.8 vs. 11.4/1,000 person-years [PY]; difference = 12.4/1,000 PY; aHR 1.65, 95% CI 1.17-2.32). While the highest ESLD incidence occurred with progression to cirrhosis (difference vs. stable/regressed disease = 56.3/1,000 PY), significant excess risk was also found with earlier transitions, including from simple steatosis to incident fibrosis (difference vs. stable/regressed disease = 18.9/1,000 PY). In contrast, all-cause mortality rates did not appear to differ when NAFLD progression was compared to stable/regressed disease (difference = 4.7/1,000 PY; aHR 0.99, 95% CI 0.78-1.24). In a nationwide, real-world cohort of patients with paired NAFLD biopsies, histological disease progression contributed to significantly higher rates of developing incident ESLD, but did not appear to impact all-cause mortality.