Population‐based epidemiology study of autoimmune hepatitis: A disease of older women?

Abstract Background and Aim: The etiology of autoimmune hepatitis (AIH) is unknown, and limited epidemiological data are available. Our aim was to perform a population based epidemiological study of AIH in Canterbury, New Zealand. Methods: To calculate point prevalence, all adult and pediatric outpatient clinics and hospital discharge summaries were searched to identify all cases of AIH in the Canterbury region. Incident cases were recruited prospectively in 2008. Demographic and clinical data were extracted from case notes. Both the original revised AIH criteria and the simplified criteria were applied and cases were included in the study if they had definite or probable AIH. Results: When the original revised criteria were used, 138 cases (123 definite and 14 probable AIH), were identified. Prospective incidence in 2008 was 2.0/100 000 (95% confidence interval [CI] 0.8–3.3/100 000). Point prevalence on 31 December 2008 was 24.5/100 000 (95% CI 20.1–28.9). Age‐standardized (World Health Organization standard population) incidence and prevalence were 1.7 and 18.9 per 100 000, respectively. Gender‐specific prevalence confirmed a female predominance, while ethnicity‐specific prevalence showed higher prevalence in Caucasians. 72% of cases presented after 40 years of age and the peak age of presentation was in the sixth decade of life. Conclusions: This is the first and largest population‐based epidemiology study of AIH in a geographically defined region using standardized inclusion criteria. The observed incidence and prevalence rates are among the highest reported. The present study confirms that AIH presents predominantly in older women, with a peak in the sixth decade, contrary to the classical description of the disease.