Trends in Incidence of Autoimmune Liver Diseases and Increasing Incidence of Autoimmune Hepatitis

Autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), and primary sclerosing cholangitis (PSC) are autoimmune liver diseases of unknown etiology. We studied trends in incidences of AIH, PBC, and PSC in a population-based prospective study Canterbury, New Zealand. We collected data on patients with AIH (n = 99), PBC (n = 26), or PSC (n = 47) from public hospitals and private practices in Canterbury from 2008 through 2016. Diagnoses were made based on international standardized criteria. We calculated incidence rates for the time periods of 2008–2010, 2011–2013, and 2014–2016 and compared them using 2-tailed mid-P exact tests. Overall incidence rates were 1.93 per 100,000 for AIH (95% CI, 1.58–2.34), 0.51 per 100,000 for PBC (95% CI, 0.33–0.73), and 0.92 per 100,000 for PSC (95% CI, 0.68–1.21). The incidence of AIH was significantly higher during the period of 2014–2016 (2.39 per 100,000; 95% CI, 1.76–3.23) than during the period of 2008–2010 (1.37 per 100,000; 95% CI, 0.91– 2.06) (P < .05). Incidences of PBC and PSC did not change significantly. In 2016, prevalence values were 27.4 per 100,000 for AIH (95% CI, 23.58–32.0), 9.33 per 100,000 for PBC (95% CI, 7.13–12.05), and 13.17 per 100,000 for PSC (95% CI, 10.56–16.42). In a population-based prospective study, we found that the incidence of AIH was significantly higher in the 2014–2016 period than the 2008–2010 period; incidences of PBC and PSC were unchanged over the same period. Further studies are needed to determine the reasons for changes in incidence of autoimmune liver diseases.