Obesity is an ever-increasing public health issue and the single most prevalent health risk among women in the United States today.1 More than one third of the U.S. adult female population is obese. Recently, data from a large prospective cohort study of subjects in the NIH-AARP Diet and Health Study showed that being overweight in midlife increases one's risk of death by 20–40%, even if one is healthy and has never smoked.2 Being overweight or obese is associated with the development of type 2 diabetes, cardiovascular disease, cancer, sleep disorders, gallbladder disease, and arthritis.3–5 It can also adversely affect reproductive health in women, increasing the risk of infertility,6 irregular menses,6 polycystic ovarian syndrome,7 and high-risk pregnancies.8 Obesity is a risk factor for both urinary and fecal incontinence.9–11 A recent study found a particularly high prevalence of urinary and anal incontinence in a cohort of 178 morbidly obese (body mass index [BMI] 40 kg/m2 or more) women undergoing consultation for bariatric surgery.12 The prevalence of urinary incontinence was 66.9% and anal incontinence 32% (17.4% when considering liquid and solid stool and not flatus).
In 1991, the National Institutes of Health Consensus Development Conference13 established criteria for surgical intervention in the morbidly obese. These criteria specify that patients with a BMI of 40 kg/m2 or greater are potential candidates for surgery if they strongly desire substantial weight loss, their obesity severely affects quality of life, they are medically fit, and they have failed dietary weight loss therapy. The majority of patients who undergo bariatric surgery are women.14
Previous research on weight loss in morbidly obese women undergoing bariatric surgery has shown a positive effect on symptoms of urinary incontinence. One report of 12 women with urinary incontinence (mean BMI preoperatively, 49.4±7.9 kg/m2) who underwent bariatric surgery reported a decrease in bothersome urinary incontinence symptoms in nine of the 12 women (P=.004).15 Seven of 10 subjects with stress incontinence and eight of nine subjects with urge incontinence had resolution of symptoms. A larger study6 reported gynecologic and obstetric outcomes 2–5 years postoperatively in a cohort of 138 morbidly obese women who lost 50% or more of their excess weight with open bariatric surgery. Prevalence of urinary incontinence symptoms was significantly reduced from 61.1% preoperatively to 11.6% postoperatively (P<.001). No study has reported the effect of weight loss on symptoms of fecal incontinence.
The primary objective of this study was to examine changes in the prevalence and severity of urinary and fecal incontinence in morbidly obese women 6 and 12 months after laparoscopic weight loss surgery. The secondary objective was to examine predictors of regaining urinary continence 12 months after surgery.
MATERIALS AND METHODS
Participants in the study were women with BMI of 40 kg/m2 or more who underwent bariatric surgery between October 2003 and February 2005. Approval was obtained from the University Institutional Review Board for Human Use.
Before the initial office visit, patients accessed an existing Web site established by one of the investigators (R.H.C.). From the Web site, they printed patient information forms, which they completed at home and returned at their clinic visit.
All women underwent laparoscopic Roux-en-Y gastric bypass, a well-accepted and studied procedure in the bariatric literature.14,16,17 The highest rate of weight loss typically occurs 5–6 months postoperatively and then tends to level off.16,18
Five to 6 months after surgery, participants returned to the clinic, at which time they were weighed and completed questionnaires assessing symptoms of urinary and fecal incontinence. At 12 months after surgery, participants were contacted by telephone and asked to repeat and mail in their questionnaires.
Self-administered patient forms were used to collect baseline demographic information and medical and obstetric history, including presence of arthritis, hypertension, diabetes, sleep apnea, use of diuretics and hormone replacement therapy, hysterectomy, and current smoking. Race was self-reported and included in this study to demonstrate the representativeness of the sample. Instruments used to measure urinary symptoms included the Medical, Epidemiological, and Social Aspects of Aging Questionnaire,19 the Urogenital Distress Inventory (short form),20 and the Incontinence Impact Questionnaire (short form).20 The Medical, Epidemiological, and Social Aspects of Aging Questionnaire is a 15-item self-administered questionnaire that assesses the presence and frequency of urinary incontinence symptoms. It yields two subscales, one for stress incontinence and one for urge incontinence. The presence of urinary incontinence was the primary outcome measure and was defined as a response of “sometimes” or “often” to any item on the questionnaire. Fecal incontinence was assessed by asking participants “Do you have any uncontrolled anal leakage?” and “If yes, specify gas, liquid, solid or a combination.”
Changes from baseline to the 12-month follow-up were tested using the McNemar test for paired proportions for dichotomous outcomes and the paired t test for continuous outcomes. Selected clinical and demographic variables were examined as potential predictors of change in urinary continence status at 12 months, using simple logistic regression models. Characteristics or factors with P≤.05 were judged to be significantly associated with odds of regaining continence. Predictors of regaining fecal continence were not examined because the sample of participants with fecal incontinence was too small for standard statistical methods. All analyses were performed using SAS 9.0 (SAS Institute Inc, Cary, NC).
The sample size of 101 pairs achieves 83% power to detect an odds ratio of 2.5 using a two-tailed McNemar test with a significance level of .05. This study therefore had sufficient power to identify comorbidities having 2.5 times the odds of being present before surgery as compared with after surgery. The odds ratio is equivalent to a difference between two paired proportions of 0.20, which occurs, for example, when the proportion reporting the comorbidity before surgery but not after is 0.33 and the proportion not reporting the comorbidity before surgery but after is 0.13.
Of 194 women who completed a consultation for bariatric surgery, 180 had a BMI of 40 kg/m2 or more, and 101 of these women underwent bariatric surgery. Data were available on 83 women at the 6-month follow-up and 99 women at the 12-month follow-up. The 101 participants ranged in age from 20 years to 55 years (mean 40.2 years). Body mass index ranged from 40 kg/m2 to 77 kg/m2, with a mean BMI of 48.9±7.2 kg/m2. Characteristics of the participants are presented in Table 1.
Mean BMI decreased from 48.9±7.2 kg/m2 (range 40–77) before surgery to 35.3±6.5 kg/m2 (range 25–58) at the 6 month follow-up and 30.2±5.7 kg/m2 (range 19–45) at the 12-month follow-up. Mean decrease in BMI was 13.0±3.5 kg/m2 (range –1 to 22) at 6 months and 18.8±4.5 kg/m2 (range 11–22) at 12 months. The distributions of BMI values before and 12 months after surgery are displayed in Figure 1A and B.
Regarding the primary outcome, the prevalence of urinary incontinence decreased significantly from 66.7% before surgery to 41.0% at 6 months and 37.0% at the 12-month follow-up (P<.001; Table 2). Similar patterns of change were observed for the subtypes of incontinence, stress, urge, and mixed urinary incontinence (all P<.001). Although the findings for the subtypes of incontinence remain significant even after a Bonferroni correction for multiple testing, we caution the reader that the outcomes are all associated with one another. Therefore, one could expect that if one outcome demonstrated significant changes then the other outcomes would as well.
Reductions in prevalence of incontinence were significantly associated with the magnitude of the decreases in BMI (P=.01; Fig. 2), such that greater weight loss resulted in more patients regaining urinary continence. Among incontinent women who lost at least 18 BMI points, 71% had regained urinary continence 12 months after surgery. Variables not associated with changes in urinary continence status were age (P=.39), sleep apnea (P=.21), arthritis (P=.71), hypertension (P=.53), diabetes (P=.96), and parity (P=.55).
In addition to reduction in the prevalence of urinary incontinence, the severity of incontinence was also significantly reduced, as indicated by both the Medical, Epidemiological, and Social Aspects of Aging Questionnaire stress and urge incontinence scores. Reductions in these scores were not correlated significantly with magnitude of change in BMI at 12 months (urge score Pearson r=.16, P=.12; stress score r=.20, P=.06).
Changes in scores on the Urogenital Distress Inventory and Incontinence Impact Questionnaire at 12 months after surgery are displayed in Table 2. Consistent with the other measures, scores on these instruments indicate significant reductions in urinary symptoms and effect on quality of life after laparoscopic gastric bypass.
Changes in fecal incontinence varied depending on whether flatal incontinence was included or examined separately (Table 3). There was a significant decrease in loss of solid or liquid stool, from 19.4% before surgery to 9.1% at 6 months, and 8.6% 12 months after surgery (P=.018). Conversely, there was a significant increase in the percentage of patients with flatal incontinence only, from 12.9% preoperatively to 20.8% at 6 months, and 30.1% at 12 months (P=.004). Combining loss of solid stool, liquid stool, and gas, the change in prevalence 6 and 12 months after surgery was not significant (P=.32). Predictors of resolution of fecal incontinence could not be examined because the sample of participants with fecal incontinence was too small for standard statistical methods.
The results of this study clearly show that the prevalence of urinary incontinence decreases significantly after laparoscopic gastric bypass surgery. Reduction in the prevalence of urinary incontinence has been demonstrated in previous weight loss studies, both in the context of bariatric surgery6,15 and with more modest weight loss in traditional weight loss programs.21 The present study showed not only reduction in the presence of urinary incontinence, but improvements on validated instruments designed to measure severity (frequency) of incontinence symptoms (Medical, Epidemiological, and Social Aspects of Aging Questionnaire), the effect of incontinence on the patient's lifestyle (Incontinence Impact Questionnaire), and distress from urogenital symptoms (Urogenital Distress Inventory).
The effect of weight loss on urinary symptoms is comparable to what has been reported in patients undergoing surgery for stress incontinence.22 For example, in a cohort of subjects undergoing the tension-free vaginal tape for incontinence, there was a 64% reduction in Urogenital Distress Inventory score at 6 months after surgery, which was maintained to 1 year, as compared with a 57% reduction with bariatric surgery in the present study. Similarly, bariatric surgery resulted in a 61% reduction in effect score at 12 months as compared with approximately 80% for incontinence surgery. The incontinence surgery cohort was older and presented with higher symptom and effect scores, but the comparative magnitude of change is impressive.
This study also extends prior findings by examining changes over time and exploring predictors of continence status. It is noteworthy that reductions in incontinence paralleled reductions in weight, with the greatest changes in the first 6 months after surgery and more gradual changes in the subsequent 6 months. Consistent with this finding, the magnitude of change in BMI was a strong predictor of continence being recovered. Also, sleep apnea and diabetes, conditions that would be expected to improve after bariatric surgery, as well as to affect incontinence prevalence, were unrelated to regaining bladder control.
The effect of weight loss on fecal incontinence has remained an unexplored area. The present study demonstrated significant reductions in loss of liquid or solid stool. The mechanism of improvement is unknown but may be due to relief of chronic pressure on the pelvic floor that may weaken not only the urinary continence mechanism23,24 but also the internal and external anal sphincters as well. However, flatal incontinence increased after laparoscopic gastric bypass. This finding may be explained by changes in diet or digestion that cause increases in flatus and that have been previously described.25,26
One of the limitations of this study is the absence of a control group to observe changes that might occur in women who did not undergo bariatric surgery or weight loss. However, even in the absence of a control group, the observed changes in incontinence are unlikely to have occurred in women who did not lose weight. The changes were quite large, consistent with those seen in active treatment protocols, and not consistent with natural variations in continence status and remissions rates observed in epidemiologic studies.9 In addition, improvements in bladder symptoms were seen across measures, not only for presence of urinary incontinence on the Medical, Epidemiological, and Social Aspects of Aging Questionnaire, but also for symptom distress as indicated by the Urogenital Distress Inventory, for the severity of incontinence as indicated by the Medical, Epidemiological, and Social Aspects of Aging Questionnaire scores, and for the effect of incontinence on the patient's lifestyle (Incontinence Impact Questionnaire). Further, the significant association between magnitude of weight loss and reduction in prevalence of urinary incontinence strengthens the inference that improvements in continence status are attributable, at least in part, to weight loss.
Another limitation of the study is that we did not characterize patients on urodynamic parameters, nor did we measure urodynamic changes to assist in understanding the mechanisms of improvement in continence status. Incontinence associated with obesity is commonly explained by chronically elevated pressure on the bladder (leading to higher intravesical pressure) and on the pelvic floor (possibly contributing to pelvic relaxation or nerve damage). Improvements in continence status with weight loss are commonly attributed to the relief of chronically elevated bladder pressure and recovery of pelvic floor tissues and function. Previous research has shown changes in bladder pressure and other urodynamic parameters after bariatric surgery that could explain these improvements.15 However, women who undergo bariatric surgery experience a multitude of changes that may or may not play a role in improving bladder or bowel control, including changes in their medical conditions, diet, and digestion. Regardless of the specific mechanisms of therapeutic change, the potential benefits of bariatric surgery should be considered when counseling morbidly obese women about their treatment options for urinary and fecal incontinence.
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