Epidemiology of endometriosis based on real-world data in Japan

RESEARCH QUESTION: Considering the progressively delayed age of pregnancy, what is the current epidemiology of endometriosis in Japan, including its prevalence, incidence and medication patterns, as revealed by a large-scale, real-world dataset? DESIGN: A descriptive analysis of a health insurance dataset from January 2005 to July 2023. The study included adolescent girls and women aged 15 years or older with available data and at least 2 years of follow-up data. The main outcome measures were the prevalence of endometriosis, the age-specific incidence and the hypothetical cumulative incidences. RESULTS: Initially, 4,917,037 adolescent girls and women with at least 2 years of follow-up data were identified as potential participants, 285,309 of whom were diagnosed with endometriosis at 15-50 years of age. The prevalence of endometriosis increased consistently from 2006 to 2022, reaching 3.62% in 2022. The highest incidence was observed at 26 years of age. In older groups, the incidence of adenomyosis was higher than that of endometrioma. The hypothetical cumulative incidences were 37.34% for overall endometriosis and 20.08% for endometriosis treated with medications, with increasing trends observed for both conditions. CONCLUSIONS: The hypothetical lifetime incidence of endometriosis by age 50 years was approximately one-third among women, and one-fifth required medication for its treatment, highlighting the need for increased awareness and improved management in clinical settings.