Materials and Methods

This was a planned subanalysis of data collected from SISTEr, a multicenter, randomized, surgical trial in the United States comparing 2 common stress UI surgeries: Burch colposuspension and autologous rectus fascial sling. The trial of 655 community-dwelling, adult women, electing surgical treatment of stress-predominant urinary incontinence was conducted between February 2002 and June 2004. Eligibility requirements included documented pure or predominant symptoms of stress incontinence for at least 3 months and a positive standardized urinary stress test. Details of the study design and primary results have been previously reported. The study protocol was approved by the institutional review board at each of the participating institutions, and written informed consent was obtained from all participants.

Data were collected at baseline (prior to randomization) and at 24 months following surgery, the primary endpoint of the trial, using self-report questionnaires, physical examinations, and quantitative tests that included bladder diaries, weighed pad tests, and urodynamic studies. We report on 491 women who provided complete cost data at both time points (75% of women randomized and 94% of women assessed for the primary outcome at 24 months).

The 164 women excluded were younger (49 [±10] vs 53 [±10] years, P < .01), less educated (18% vs 28% with college degrees, P < .01), more likely to be diabetic (11% vs 6%, P = .02), smoked (21% vs 12%, P < .01), and less likely to have pelvic organ prolapse (65% vs 79%, Pelvic Organ Prolapse Quantification [POP-Q] stage greater than I, P < .01) and to have had nonsurgical (38% vs 48%, P = .04) or surgical (9% vs 16%, P = .03) treatment for UI compared with women included in this cost analysis.

Resources used for UI management or routine care by study participants were assessed by the question, “Over the past 7 days, please record the average number of supplies you used each day for your urinary incontinence.” Absorbent supplies included panty liners, minipads, maxipads, incontinence pads, diapers, urethral inserts/occlusive devices, toilet paper, and paper towels. Laundry use was assessed by the question, “How many loads of wash did you do during the last 7 days because of your incontinence?” and dry cleaning by the question, “How many items of clothing did you dry clean during the last 7 days because of your incontinence?”

For generalizability, we estimated the national unit costs for each type of supply, a load of laundry, and each item of dry cleaning using a survey of 14 stores in 6 states and 1 national Internet source. Primary cost data were collected in 2006 and the cost estimates were inflated to 2012 United States dollars using the general consumer price index and a multiple of 1.116 ( ftp://ftp.bls.gov/pub/special.requests/cpi/cpiai.txt ).

Mean out-of-pocket UI management cost (cost) was calculated by multiplying units of resources used by the mean cost per unit. Because the distribution of the cost data was skewed, we calculated the median and 25th and 75th percentiles (interquartile range [IQR]) as well as mean and SD for total routine care costs. We report both mean and median cost estimates because the aggregate costs to society are best summarized by mean cost multiplied by the number of people affected, whereas the cost to a typical woman who incurs any costs is best summarized by the median.

To minimize the outlier effect observed for some cost categories, Winsorization at the 90th percentile was also performed; specifically, costs and measures of incontinence above or below the 95th or 5th percentile, respectively, were reset to that limit for all multivariate analyses. Summary and univariable statistics were computed for women with any reported costs. Because routine care costs are paid out-of-pocket by affected women in the United States, the analysis is from the patient’s perspective.

Factors thought a priori to be associated with change in cost were assessed by self-report of demographic characteristics and medical history. Frequency of UI was assessed when the participant completed a 3 day voiding diary and reported by quartiles. We used total UI episodes per day for the primary variable to represent UI severity in this study.

Classification of type of UI was determined by the Michigan Epidemiological Study of Aging (MESA) questionnaire and defined as stress only if only stress UI symptoms were reported or mixed UI if both urine stress and urge UI symptoms were reported. By design all women with mixed UI had predominantly stress UI symptoms.

The amount of urine involuntarily lost was measured by 24 hour pad test weight. Condition-specific quality-of-life instruments (Incontinence Impact Questionnaire [IIQ] and Urogenital Distress Inventory [UDI]) were administered. Pelvic organ prolapse was assessed by physical examination (POP-Q) and fecal and flatal incontinence were identified by self-report of leaking or loss of control of liquid or solid stool or gas.

We compared baseline demographic and clinical characteristics of the Burch and sling groups using χ ² and analysis of variance tests. Because no significant differences were observed between the 2 groups for either cost at baseline or change in cost from baseline to 24 months (all P > .05), the groups were combined to examine the effects of change in incontinence cost from baseline to 24 months. An intervention indicator was included in all multivariate models.

Univariate and bivariate changes in cost were analyzed using Wilcoxon signed rank test. Factors measured at baseline considered a priori as possible predictors of change in cost were examined using multivariate mixed models, including age, ethnicity, education, baseline body mass index, annual household income, report of 3 or more urinary tract infections per year, POP-Q stage, fecal incontinence, diabetes, prior nonsurgical UI treatment, menopause, smoking, surgery group, and accounting for site clusters.

Our sample provided 80% power to detect a change of cost of $2.63 per week. To assess whether successful treatment was associated with greater reduction of cost compared with failed treatment, we compared the cost among women who experienced success for overall UI measures as defined for the clinical trial (defined as a negative pad test, no urinary incontinence recorded in a 3 day diary, negative cough and Valsalva stress tests, no self-reported symptoms, and no retreatment for the condition) and success for stress incontinence specifically (defined as meeting the latter 3 criteria) using multivariable mixed models. A value of P < .05 was considered statistically significant. All analyses were carried out using SAS version 9.1 (SAS Institute, Cary, NC).

Results

Four hundred ninety-one women provided information on urinary incontinence management cost at both baseline and 24 months after surgery. They had a mean (±SD) age of 53 (±10) years and most were white (80%; Table 1 ). The distribution of reported annual household income was less than $40,000 (37%), $40,000-99,999 (44%), and $100,000 or more (19%).

At baseline, most women (85%) reported at least daily frequency of urinary incontinence, with a mean of 23 (±21) incontinent episodes per week. No differences were observed between the Burch and fascial sling group participants for baseline characteristics. At 24 months after surgery, the average number of incontinence episodes per week reported on voiding diaries decreased from 23 to 3 (a decrease of 86%, P < .001) and 68% of the women were dry on subjective and objective assessment, meeting the criteria for successful treatment.

Mean and median weekly out-of-pocket urinary incontinence management cost per participant were $16.60 ± $27.49 and $9.39 (25th to 75th percentile IQR, $3.78–19.75; range, $0–248) at baseline and decreased to $4.57 ± $15.37 and $0.10 (IQR, $0–3.39; range, $0–238) at 24 months ( P < .001; Table 2 ). This represents a decrease of 72% ($625 per woman per year) in annual mean cost for all women. The reduction in weekly cost for both surgery groups did not differ significantly (–$12.09 for Burch vs –$11.98 for fascial sling; P = .49).

Table 2

Weekly patient costs for incontinence management and change in cost at 24 months overall and by item (in 2012 US dollars)

Variable	Number (percent of total) using this resource	Baseline costs per week a		Total cost, %	Change in cost at 24 months a
		Mean (SD)	Median (IQR)		Mean (SD)	Median (IQR)
Total UI related cost	464 (95%)	16.60 (27.49)	9.39 (3.78–19.75)	100%	–12.03 (29.22)	–6.38 (–16.85 to –1.45)
Pad cost	410 (84%)	10.49 (24.62)	4.94 (0.97–11.81)	63%	–7.60 (26.18)	–3.22 (–9.62 to 0.0)
Paper (towels, toilet paper) cost	244 (50%)	0.96 (2.01)	0.0 (0.0–1.31)	6%	–0.54 (2.26)	0 (–0.85 to 0.0)
Incontinence-related laundry cost	276 (56%)	3.20 (4.20)	2.50 (0.0–5.0)	19%	–2.60 (4.42)	–0 (–5.0 to 0.0)
Dry cleaning–related cost	59 (12%)	1.97 (7.28)	0.0 (0.0–0.0)	12%	–1.31 (8.37)	0 (0.0–0.0)

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