OBJECTIVES: Non-alcoholic steatohepatitis (NASH) is a progressive form of non-alcoholic fatty liver disease (NAFLD). Due to the invasive diagnostic process and non-specific symptoms, NASH may be undetected and underreported. Thus, there is limited knowledge of NASH prevalence, with prior estimates based on expert consensus or data mainly pertaining to specific subpopulations. Our study aimed to describe the NASH incidence and prevalence in England using real-world routinely collected population data.

METHODS: We used linked primary (Clinical Practice Research Datalink Aurum) and secondary (Hospital Episode Statistics) care data in England to detect individuals with NASH from 2011-2021. We employed four definitions to identify NASH: 1) ≥1 NASH-code diagnosis, 2) either ≥1 NASH-coded inpatient or ≥2 NASH-coded outpatient or primary care diagnoses, 3) NAFLD-coded diagnosis with subsequent liver biopsy, and 4) NAFLD-coded diagnosis and ≥2 subsequent elastography and fibrosis score. We described the incidence and prevalence of NASH based on these definitions.

RESULTS: Definitions 1-4 identified 2,696, 2,101, 2,041, and 1,587 patients, respectively, with 78% overlap between definitions 1 and 2 and low overlap between definitions 1-3 and 1-4 (Jaccard index = 0.13 and 0.03, respectively). Incidence for definitions 1-3 was similar over time (~2.00-4.00/100,000 person-years), while incidence using definition 4 increased steadily over time (~0.04 to ~4.17/100,000 person-years). Overall NASH prevalence in this study was 39 per 100,000 people.

CONCLUSIONS: NASH prevalence in our study was lower than estimates generated for the UK or other European countries (3-%), however, the majority of prior estimates are not based on general population real-world data sources. Given the diagnostic challenges of NASH, the incidence and prevalence may be underestimated in our study. The difference in patients picked up in definition 4 could be attributed to increased use of non-invasive tests over time, possibly representing those with NAFLD at-risk of progression rather than those with NASH.