Objective: To investigate the relationship between the symptom of mixed urinary incontinence and incontinence severity, urodynamic findings, and treatment response.
Methods: This is a secondary analysis of data from 553 women randomized into a double-blind, placebo-controlled study evaluating duloxetine (serotonin-norepinephrine reuptake inhibitor) for the treatment of predominant stress urinary incontinence. Assessment variables included incontinent episode frequency, the Incontinence Quality of Life Questionnaire (I-QOL), and the Patient Global Impression of Severity Scale (PGI-S). Urge symptoms were identified with three urge I-QOL questions not included in corrected I-QOL calculations.
Results: At baseline, 171 women (31%) had mixed urinary incontinence. They had more severe baseline urinary incontinence than did those with stress urinary incontinence (mean incontinent episode frequency 14.3 versus 10.5; PGI-S normal or mild 26.5% versus 70.4%; mean corrected I-QOL 59.1 versus 79.9; all Ps <.001). Baseline urodynamics were performed on a subset of 86 women. Subjects with both urodynamic stress incontinence and detrusor overactivity had less severe incontinence compared with subjects with only urodynamic stress incontinence. Both mixed urinary incontinence and stress urinary incontinence groups had significant decreases in median incontinent episode frequency at a 40 mg per day (62% and 58%, respectively) and 80 mg per day (63% and 65%) duloxetine dose compared with placebo (33% and 44%; all Ps <.05). Response was not dependent on the type of symptoms (interaction P =.47).
Conclusion: For women presenting with predominant stress urinary incontinence symptoms, the major determinant of concurrent urge symptoms was incontinence severity and not the pathophysiologic condition(s) causing the incontinence; duloxetine demonstrated equal efficacy for women with mixed urinary incontinence and pure stress urinary incontinence.