South Korea offers public health insurance for all Koreans. Consequently, Korea's National Health Insurance Service can access the medical records (sex, age, surgery name, prescription drug name, diagnosis name, type of medical insurance, hospitalization, and outpatient treatment) of most Koreans (approximately 51 million people). The Health Insurance Review and Assessment Service is a nationwide organization that arbitrates health insurance payment disputes between the NHIS and medical institutions. Therefore, the HIRA has access to most of the National Health Insurance Corporation's medical record information for Koreans. This population-based retrospective cohort utilized HIRA's health insurance data study (January 1, 2007, to December 31, 2020).
The International Classification of Diseases, 10th Revision (ICD-10) and Korea Health Insurance Medical Care Expenses (2016, 2019 edition) were utilized for the analyses in this study. In this study, the hysterectomy group consisted of women aged 40 to 59 who underwent hysterectomy for uterine leiomyoma or adenomyosis between January 1, 2011, and December 31, 2014. The day of the hysterectomy was designated as the inclusion date. The control group consisted of women aged 40 to 59 who visited a medical facility for a checkup between January 1, 2011 and December 31, 2014. Those who had a hysterectomy were not included in the control group. The inclusion day was designated as the date of the initial health examination visit. In all groups, patients with any cancer (any Cxx) were excluded before the 180th day of inclusion. For the selected hysterectomy group and control group, 1:1 propensity score matching was performed for age in 5-year intervals, year of inclusion, socioeconomic status (SES), parity, region, Charlson comorbidity index (CCI), adnexal surgery before inclusion, menopause before inclusion, menopausal hormone therapy, and pelvic organ prolapse before inclusion.
Information about the bladder, ureter, and kidney cancer diagnoses was derived from the Korean Cancer Register using ICD-7 nomenclature.