Impact of overactive bladder on quality of life and resource use: results from Korean Burden of Incontinence Study (KOBIS)

Background: To evaluate the impact of overactive bladder (OAB) on quality of life (QOL), resource use and productivity loss in patients recruited from six hospitals in Korea. Methods: This cross-sectional survey recruited 625 OAB patients between July to December 2013. Patients were categorised into four groups based on the average number of urinary incontinence (UI) episodes over the past three days (0, 1, 2-3 and >= 4 UI/day). QOL was measured using the Incontinence-Specific Quality of Life Instrument (I-QOL), the Overactive Bladder Questionnaire (OAB-q), and a generic health-related utility instrument (EQ-5D). Information on hospital and clinic visit frequency, and continence pads use were also collected. Work productivity was assessed using the Work Productivity and Activity Impairment (WPAI) questionnaire. Between group differences were assessed using ANOVA. Multivariable regression analyses were performed to examine the independent effects of OAB symptoms on QOL. Results: Severity of UI showed a significant linear relationship with QOL, with clinically meaningful differences between each UI severity category. Compared to the dry category, patients in the most severe category (>= 4 UI/day) had significantly lower I-QOL scores (69.8 vs 42.6; p < 0.0001), greater symptom bother on the OAB-q (30.4 vs 64.6; p < 0.0001), and poorer EQ-5D utility (0.848 vs 0.742; p < 0.001). Multivariable analyses showed that UI severity, frequency, urgency, and nocturia are independently associated with poorer QOL. Incontinence severity is also significantly associated with cost of incontinence pads (p < 0.0001), and a greater interference with work and regular activities (p = 0.001), however, no significant difference in hospital and clinic visits were observed. Conclusion: Severity of UI is a key contributor to the disease burden of OAB in Korean patients, even after taking into account the impact of other symptoms associated with OAB.