Epidemiology

Autoimmune hepatitis (AIH) occurs globally in people of all aged and ethnicities. One meta-analysis of 22 studies found a pooled worldwide incidence of 1.37 per 100,000 persons and prevalence of 17.44 per 100,000 persons, with a high level of heterogeneity between studies.[4] Sub-group analysis suggested that incidence rates were similar worldwide, but prevalence was lower in Asian than in European and American populations; this difference may be due to genetic factors, as Europeans and North American populations are mainly white, with a high frequency of human leukocyte antigen (HLA)-DR3 and HLA-DR4 markers. An increase in incidence of type 1 AIH, which seems to represent a true increase of the disease, has been reported in Denmark, rising from 1.37 to 2.33 cases per 100,000 individuals per year between 1994 and 2014. This increase was also reflected by an increase in prevalence.[5]

Women are more frequently affected than men.[5][6]​​[7][8][9][10]​ Incidence rates for women in Europe are 1.2 to 3.05 per 100,000 population, compared with 0.26 to 0.89 per 100,000 population for men​.[11]

Type 1 AIH is the most common form; 78% of patients are women (female:male ratio is 4:1).[12] Type 1 AIH demonstrates a bimodal age distribution, most frequently affecting people between the aged of 10 and 30 years and 40 and 60 years.[13] Older peak aged of onset of AIH (>60 years) have been reported in Denmark and New Zealand.​[5][6]​​

Type 2 AIH mainly affects children; again, the majority of patients are female.[3][13][14] Prevalence is unknown. In one study in Canada that included 159 children and adolescents with AIH, the annual incidence of AIH was 0.23 cases per 100,000 children; type 1 AIH was diagnosed 5.5 times more frequently than type 2 AIH.[10]​​​​

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