Effectiveness of Local Estrogen Therapy in Postmenopausal Urinary Incontinence : A Systematic Review of Randomized Controlled Trials and Primary Studies

Abstract

Introduction: Urinary incontinence affects 38–55% of women over 60 years and is a major quality-of-life limiting component of genitourinary syndrome of menopause (GSM). Oestrogen receptors are densely expressed throughout the trigone, urethral epithelium, periurethral vasculature, and pelvic connective tissue, providing strong biological rationale for topical hormonal repletion. However, systemic oestrogen worsens incontinence while local preparations improve it—a dissociation frequently conflated in earlier syntheses. This review quantified the effectiveness of local oestrogen therapy on continence outcomes in postmenopausal women.

Methods: The study strictly adhered to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) 2020 guidelines. Eligible designs included RCTs, cohort, case-control, and cross-sectional studies. Sixteen outcome domains were prespecified. Risk of bias assessed with RoB 2, ROBINS-I, and NOS; certainty with GRADE. Synthesis was narrative with effect-direction plots, vote-counting, and exploratory ROC analysis of baseline predictors of response.

Results: Thirty-one primary studies (24 RCTs, 3 prospective cohorts, 4 retrospective/cross-sectional) comprising 12,947 women in interventional studies plus 1,897,594 in database cohorts were included. Local oestrogen produced consistent significant benefit for urgency urinary incontinence, urgency, daytime frequency, and nocturia. In the largest placebo-controlled trial of vaginal 17β-estradiol 10 µg, urgency incontinence improved significantly at 4 and 12 weeks (p=0.013) with parallel rise in urethral maturation index (p<0.001) and fall in vaginal pH (p<0.001). Low-dose intravaginal estriol improved subjective incontinence in 68% vs 16% controls, with significant increases in maximum urethral pressure, closure pressure, and abdominal pressure transmission ratio. Contextual pooled estimates showed ORs of 0.12 (95% CI 0.05–0.29) for stress incontinence, 0.22 (0.16–0.32) for urgency incontinence, 0.11 (0.06–0.18) for urgency, and 0.14 (0.05–0.36) for recurrent UTI. Recurrent UTI fell from 5.9 to 0.5 episodes/patient-year (p<0.001), and by 51.9% in a 5,638-woman cohort; in a 1,891,956-woman database, vaginal oestrogen was associated with lower odds of sepsis, hospitalization, and mortality. Local oestrogen matched oral oxybutynin for reducing frequency with fewer anticholinergic adverse events. Systemic absorption remained within postmenopausal range; no endometrial hyperplasia or carcinoma was reported over 12 months. Evidence for pure stress incontinence was weaker. Exploratory ROC analysis showed a composite model (age, severity, maturation index, pH, adherence) discriminated responders with AUC 0.81 vs 0.59–0.74 for single variables.

Discussion: Effect direction is remarkably consistent across four decades: restoring vaginal and urethral epithelium reduces the storage symptom cluster of GSM. Effect is largest for urgency-predominant phenotype, intermediate for frequency, nocturia, and recurrent infection, and smallest for pure stress incontinence—where deficit is mechanical support failure rather than hormone-responsive mucosa. Principal limitations are heterogeneity of outcome instruments, short follow-up (rarely >12 months), small samples, and failure to report continence endpoints in GSM trials.

Conclusion: Local oestrogen is effective, well-tolerated, and biologically coherent for urgency-predominant urinary incontinence and associated storage symptoms in postmenopausal women, and reduces recurrent UTI with favourable safety. It should be offered as adjunctive first-line therapy alongside pelvic floor muscle training, and as an antimuscarinic-sparing option. Evidence for pure stress incontinence as monotherapy is insufficient. Adequately powered trials with continence-specific primary endpoints and follow-up beyond 12 months are required.