Hysterectomy is not associated with increased risk of urinary incontinence-a northern Finland birth cohort 1966 study.

Introduction: Hysterectomy has been suggested to increase the risk of urinary incontinence (UI), although evidence is controversial. In our population-based cohort study, we aimed to assess the independent effect of hysterectomy on the risk of de novo UI.

Material And Methods: This is a population-based cohort study on the women of the Northern Finland Birth Cohort 1966 (n = 5889). We identified all hysterectomies among the cohort (n = 461) using the national Care Register for Health Care and classified them according to surgical approach into laparoscopic (n = 247), vaginal (n = 107), and abdominal hysterectomies (n = 107). Women without hysterectomy formed the reference group (n = 3495). All women with UI diagnoses and operations were identified in the register, and women with preoperative UI diagnosis (n = 36) were excluded from the analysis to assess de novo UI. Data on potential confounding factors were collected from registers and the cohort questionnaire. Incidences of different UI subtypes and UI operations were compared between the hysterectomy and the reference groups, and further disaggregated by different hysterectomy approaches. Logistic regression models were used to analyze the association between hysterectomy and UI, with adjustments for several UI-related covariates.

Results: We found no significant difference in the incidence of UI diagnoses or the rate of subsequent UI operations between the hysterectomy and the reference groups (24 [5.6%] vs. 166 [4.7%], p = 0.416 and 14 [3.3%] vs. 87 [2.5%], p = 0.323). Hysterectomy was not significantly associated with the risk of any subtype of UI (overall UI: OR 1.20, 95% CI 0.77-1.86; stress UI (SUI): OR 1.51, 95% CI 0.89-2.55; other UI: OR 0.80, 95% CI 0.36-1.74). After adjusting for preoperative pelvic organ prolapse (POP) diagnoses, the risk was decreased (overall UI: OR 0.54, 95% CI 0.32-0.90; other than SUI: OR 0.40, 95% CI 0.17-0.95). Regarding different hysterectomy approaches, the risks of overall UI and SUI were significantly increased in vaginal, but not in laparoscopic or abdominal hysterectomy. However, adjusting for preoperative POP diagnosis abolished these risks.

Conclusions: Hysterectomy is not an independent risk factor for de novo UI. Instead, underlying POP appears to be a significant risk factor for the incidence of UI after hysterectomy.