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

Background & Aims: 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.

Methods: 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.

Results: 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).

Conclusions: 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.