South Korea offers public health insurance for all Koreans. Consequently, Korea's National Health Insurance Service (NHIS) 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 (HIRA) 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. It was determined that hysterectomy and adnexal surgery were performed simultaneously when adnexal surgery (oophorectomy, salpingo-oophorectomy, salpingectomy, ovarian cystectomy, additional adnexectomy, incision and drainage of ovarian cysts, ovarian wedge resection) was performed on the same day as hysterectomy. 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) or any urinary incontinence {N39.3 (stress incontinence), N39.40 (urge incontinence), N39.41 (mixed incontinence), and N39.48 (other specified urinary incontinence)} 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.
Stress urinary incontinence was defined as the occurrence of stress incontinence surgery {Transvaginal Approach (R3564, R3565), Abdominal Approach (R3562), Foreign Material or Autologous Fat Injection (R3563)} with a urinary incontinence diagnosis code (N39.3, N39.4).
If the inclusion area was outside of a metropolitan region, the region was classified as rural. When the form of health insurance was medical aid, SES was seen to be low. The CCI was computed with diagnostic codes from one year before the inclusion date to the inclusion date. Parity was determined based on the identified deliveries within the study period. Adnexal surgery was defined as at least one adnexal procedure before hysterectomy. Menopause was defined as at least two visits to a medical facility for menopause (N95.x menopausal and other perimenopausal disorders, M80.0 postmenopausal osteoporosis with pathological fracture, M81.0 postmenopausal osteoporosis, E28.3 premature menopause) before hysterectomy. If the patient was initially prescribed MHT (tibolone, estradiol hemihydrate, estradiol valerate, dydrogesterone, norethisterone acetate, drospirenone, medroxyprogesterone acetate, or cyproterone) at least 180 days before inclusion, they were considered to have MHT before inclusion.
SAS Enterprise Guide 7.15 (SAS Institute Inc) and R 3.5.1 (The R Foundation for Statistical Computing) were utilized for statistical analysis in this study. A p value of 0.05 or less was considered statistically significant in all analyses in this study, and a two-sided test was performed. For the analysis of categorical variables, the Cochran‒Mantel‒Haenszel test was utilized, whereas the Wilcoxon signed rank test was used to analyze continuous variables. Standardized differences were utilized to assess matched variables.
After adjusting for confounding variables, a stratified Cox regression model was utilized to evaluate the SUI risk of hysterectomy. The first day for Cox analysis was the inclusion date for each group, and the last day was the date of death or December 31, 2020. When the percentage of missing values was less than 10%, the pairwise deletion method was implemented, and when the percentage was greater than 10%, the regression imputation method was implemented. A stratified Cox regression analysis was performed on SUI risk following laparoscopic hysterectomy to validate our study's findings.