Determinants of urinary incontinence in a population of young and middle-aged women.

Background: Urinary incontinence and genital prolapse are prevalent conditions in the female population. The aim of this study was to study possible determinants of female urinary incontinence in a population-based sample of young and middle-aged women.
Methods: Of 641 eligible women aged 20-59 years in a primary health care district, 487 (76%) responded to a questionnaire and accepted an invitation to a gynecological examination. The examination included digital assessment of the pelvic floor muscle strength (PFMS). Genital prolapse presence (cystocele, rectocele, uterine prolapse or absence of the urethrovesical crease) was graded in relation to the vaginal introitus.
Results: The prevalence of urinary incontinence was 28%, 3.5% having daily leakage. Stress urinary incontinence was the dominant type. The odds ratio (OR) of having incontinence increased from 1 to 3.5 with increasing age and from 1 to 2.7 with increasing parity. The OR also increased with decreasing PFMS; from 1 in the group with the best PFMS to 3.4 in the group unable to contract their pelvic musculature. In addition, women with cystocele and/or absence of the urethrovesical crease had a 2.5-fold increased OR of incontinence (95% CI 1.5-4.2), smoking increased the OR 1.9 times (95% CI 1.1-3.2) and estrogen replacement therapy (ERT) increased the OR 2.9 times (95% CI 1.4-5.9). There were no significant correlations with the presence of chronic disease, episiotomy or the birth weights of children but small non-significant correlations with performed hysterectomy and the woman's weight.
Conclusions: Urinary incontinence is a frequent symptom in the female general population and related to age, pelvic floor muscle strength, genital prolapse, smoking, parity and estrogen replacement therapy.