The placebo response associated with stress urinary incontinence (SUI) is sizeable but poorly understood. The aim of this study was to examine the relationship between previous treatment experience and baseline urinary incontinence severity with placebo response.Study design
Nine hundred twenty-one women ages 24 to 83 years received placebo in 4 12-week randomized trials evaluating duloxetine for SUI in 16 countries in Africa, Australia, Europe, and North and South America. Incontinence episode frequency (IEF) was calculated before and after randomization with entries from subject-completed real-time diaries. At baseline, subjects reported on their experience with previous continence surgery and with current pelvic floor muscle training (PFMT) with standardized questions. Analyses included Pearson correlations and the Wilcoxon two-sample test, and were based on intent-to-treat principles.Results
The placebo group averaged 17 IEF per week at baseline. Fifty-five percent of placebo-treated subjects averaged ≥ 14 IEF/wk, 11.8% had previous continence surgery, and 16.5% currently performed PFMT. The overall median decrease in IEF with placebo was 33%, but ranged from 11% to 57% for individual countries. The placebo response was lower in women with more severe SUI (29.6% vs 36.4%, P = .07), in those who had previous continence surgery (25.0% vs 33.3%, P = .26), and for those using PFMT (23.6% vs 33.3%, P = .02). There was a significant positive correlation (rho = .44; P < .0001) between the placebo response within a country and that country's use rate for PFMT.Conclusion
Treatment naivete and less severe incontinence are associated with an increased placebo response in clinical trials for stress urinary incontinence, although this difference was statistically significant only for PFMT.