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Effect of weight loss on urinary incontinence in women

Background The purpose of this research was review the epidemiology of the association of obesity and urinary incontinence, and to summarize the published data on the effect of weight loss on urinary incontinence. Methods A literature review of the association between urinary incontinence and overweight/obesity in women was performed. Case series and clinical trials reporting the effect of surgical, behavioral, and/or pharmacological weight loss on urinary incontinence are summarized. Results Epidemiological studies demonstrate that obesity is a strong and independent risk factor for prevalent and incident urinary incontinence. There is a clear dose-response effect of weight on urinary incontinence, with each 5-unit increase in body mass index associated with a 20%–70% increase in risk of urinary incontinence. The maximum effect of weight on urinary incontinence has an odds ratio of 4–5. The odds of incident urinary incontinence over 5–10 years increase by approximately 30%–60% for each 5-unit increase in body mass index. There appears to be a stronger association between increasing weight and prevalent and incident stress incontinence (including mixed incontinence) than for urge incontinence. Weight loss studies indicate that both surgical and nonsurgical weight loss leads to significant improvements in prevalence, frequency, and/or symptoms of urinary incontinence. Conclusion Epidemiological studies document overweight and obesity as important risk factors for urinary incontinence. Weight loss by both surgical and more conservative approaches is effective in reducing urinary incontinence symptoms and should be strongly considered as a first line treatment for overweight and obese women with urinary incontinence.


Introduction
Urinary incontinence affects almost 50% of middle-aged and older women, 1,2 including approximately 18.3 million women currently in the US, with an estimated increase to 28.4 million women by 2050 as our population increases and ages. 3 Urinary incontinence is associated with a profound adverse effect on quality of life 4,5 and accounts for more than $30 billion in annual direct costs in the US. 6 Risk factors for urinary incontinence include aging, childbirth, diabetes, and increased body mass index (BMI). 7 More than 50% of American women are overweight (BMI: 25-29.9 kg/m 2 ) or obese (BMI: $30 kg/m 2 ), and the prevalence of obesity is increasing by almost 6% per year. 8 Obesity directly contributes to more than 300,000 deaths per year, accounts for expenditure of more than US$100 billion per year, is associated with medical comorbidities including heart disease, hypertension, diabetes, cancer, and depression, and adversely affects quality of life. 8,9 Obesity is a potentially modifiable risk factor for developing urinary incontinence, with numerous epidemiological studies suggesting that obesity is a strong risk factor. [10][11][12][13] Each 5-unit increase in BMI is associated with a 60% increase in risk of daily incontinence, and obesity has the largest attributable risk for daily incontinence compared with other risk factors. 13 Recent data from observational studies and randomized clinical trials demonstrate that weight reduction decreases the frequency of urinary incontinence episodes among overweight and obese women. 14 Thus, weight loss represents a promising new approach to treatment of urinary incontinence, and one that produces a cascade of broader health improvements in addition to reductions in the frequency of urinary incontinence.

Methods
We systematically searched for published community-based prevalence studies with bivariate or multivariate analysis of the association between urinary incontinence and overweight/ obesity in women. Prospective case series, longitudinal studies, and randomized, controlled trials of the effect of surgical, behavioral, and pharmacological weight loss on urinary incontinence are summarized. Methods were similar to those described in a recent systematic literature review. 15 Systematic searches were done using MEdLInE (1966 and thereafter), the Cochrane Central Register of Controlled Trials, the Cochrane database of Systematic Reviews, and the database of Abstracts of Reviews of Effects. Searches were updated, thereby including evidence published up to April 2011.

Association of weight and urinary incontinence
Observational epidemiological evidence Epidemiological studies demonstrate that obesity is a strong risk factor for urinary incontinence. A recent systematic literature review examined the association between urinary incontinence and overweight/obesity in women. 15 While the definition of urinary incontinence varies according to the study, data from a large number of studies indicate that urinary incontinence in women is associated with higher BMI and weight. 10,13,[16][17][18][19][20][21][22][23][24][25][26][27][28][29] Most studies demonstrate a clear dose-response effect of weight on the prevalence of urinary incontinence, 15,16 with odds ratios (OR) of 4-5 for the maximum effect of weight on urinary incontinence ( Figure 1). A stronger association is reported between increasing weight and stress-predominant incontinence (including mixed incontinence), than for urge-predominant incontinence. 12,16,22,27,30 Each 5-unit increase in BMI is associated with an approximately 20%-70% increase in risk of daily inco ntinence 10,12,13,17,22,25,26 and, in one study, obesity had the largest attributable risk for daily incontinence compared with other risk factors. 13 Among very obese women planning weight reduction surgery (BMI . 40 kg/m 2 ), the prevalence of incontinence has been reported as 60%-70%, [31][32][33][34][35] with the prevalence of pure stress incontinence in the range of 28%-33%, pure urge incontinence 4%-21%, and mixed incontinence 32%-46%. 31,34 Longitudinal studies Overweight

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Weight loss and urinary incontinence in women longitudinal cohort studies. Over 5-10 years of follow-up, the odds of incident urinary incontinence increase by approximately 7%-12% for each 1 kg/m 2 unit increase in BMI. 36,37 The association of incident urinary incontinence with increasing weight is strongest for stress and mixed incontinence and weaker for urge incontinence, and provides evidence for a temporal relationship between a possible cause and an outcome. A prospective cohort study of women (n = 6424) from the UK observed a strong association of BMI with the onset of stress incontinence (OR for overweight and obesity 1.4 and 2.3, respectively) and overactive bladder (OR for overweight and obesity 1.3 and 1.2, respectively), with only the trend for stress incontinence reaching statistical significance. 38,39 In a community-based population of women $ 50 years with urge urinary incontinence participating in the Health and Retirement Study, predictors of incident urge urinary incontinence included obesity (OR: 1.6, 95% confidence interval [CI]: 1.2-2.1). 40 In a 5-year annual follow-up of 3301 women aged 42-52 years, incident incontinence was found in 56%, for an annual incidence of 11% per year. 36

Weight gain and incident urinary incontinence
The odds of incident urinary incontinence also increase with increasing adult weight gain. 37 Compared with women who maintained their weight within 2 kg, the OR for at least weekly incontinence was 1.44 (95% CI: 1.05-1.97) among women who gained 5.1-10.0 kg and 4.04 (95% CI: 2.93-5.56) among women who gained more than 30 kg since early adulthood (P, 0.001 for trend). Compared with women having a BMI of 21.0-22.9, women with BMI $ 35 had an OR for stress incontinence of 3.42 (95% CI: 2.48-4.72), 6.10 for urge incontinence (95% CI: 3.11-11.98), and 5.60 for mixed incontinence (95% CI: 3.17-9.88). In a longitudinal study of 1201 British women, high BMI at age 20-36 years was associated with stress urinary incontinence and severe urinary incontinence in midlife. Longstanding overweight was a stronger predictor than becoming overweight/obese after the age of 43 years (OR: 1.85, 95% CI: 0.97-3.51). 29

Body fat distribution and urinary incontinence
Little is known about the association of fat distribution, for example, abdominal adiposity estimated by waist circumference or waist-hip ratio, with urinary incontinence. In multivariable analyses including BMI, increasing waisthip ratio has been found to be an independent risk factor for stress incontinence (OR: 1.18 per 0.1 unit), but not for urge and mixed incontinence. 12 Among a cohort of Korean women, compared with women in the lowest quartile of waist circumference, the ORs for stress incontinence increased significantly in a dose-dependent relationship (1.79, 3.50, and 6.07 for the next quartiles, respectively) after adjustments for BMI. 21 Among women in the nurses' Health Study, there were highly significant trends of increasing risk of incontinence with both increasing BMI and waist circumference. 41 When BMI and waist circumference were included in models simultaneously, BMI was associated with urgency and mixed incontinence, but not stress incontinence. Waist circumference was associated only with stress incontinence. In the EPInCOnT study of 6876 incontinent norwegian women, multivariable analyses adjusting for age, parity, and BMI showed a statistically significant association between waist-hip ratio and any incontinence and mixed incontinence (both OR: 1.1 per 0.1 unit). 42 In the American Boston Area Community Health survey, each 10-cm increase in waist circumference in women was independently associated with higher prevalence of weekly urinary incontinence (OR: 1.15, 95% CI: 1.01-1.31). 43

Treatment options for urinary incontinence
The mainstay of treatment for both stress and urge urinary incontinence is bladder training, toileting assistance, and/or pelvic muscle rehabilitation. [44][45][46] These behavioral approaches are only modestly effective, and in many cases, a second line of therapy is needed. Second-line treatment for stress incontinence is frequently surgical. Among 665 women enrolled in a clinical trial of the Burch and pubovaginal sling procedures, objective stress incontinence cure rates decreased from almost 100% after surgery to 50%-65% over 2 years. 47 In a randomized equivalence trial of 597 women with stress incontinence assigned to either retropubic or transobturator midurethral slings, the rates of objective treatment success at 12 months were 80% in the retropubic sling group and 77% in the transobturator sling group. 48 Although surgery is effective, it is associated with discomfort and a prolonged recovery period, and incontinence may recur over time. 49,50 Concerns about higher rates of failure and operative complications in obese women have led to debate about the role of surgery in this population, although the safety and effectiveness of continence surgery in obese women has been supported by the literature. [51][52][53][54][55][56][57] In addition, many women prefer not to have surgery, and others, particularly obese women, are poor surgical candidates. Pharmacological therapy, primarily with anticholinergic or antimuscarinic medications, is frequently the second line of therapy for urge urinary incontinence and results in a 15%-60% reduction in weekly incontinent episodes. However, anticholinergic side effects are common and the medications must be taken chronically. 58-61 newer medications and reformulations of older drugs provide better tolerability, but long-term compliance remains low. 62,63 Approved implantable neurostimulator devices and sacral neuromodulation and intravesical botulinum toxin type A injection represent newer alternatives for the management of refractory urge urinary incontinence that have been used with success, but are more invasive and costly, [64][65][66] and in the case of the latter, not yet approved by the Food and drug Administration. new and novel treatment strategies for urinary incontinence are important to improve efficacy and provide acceptable therapeutic options for women.

Effect of weight loss on urinary incontinence
Because obesity is a potentially modifiable risk factor for urinary incontinence, weight reduction has been shown to be an effective treatment option. A beneficial effect of weight loss on the prevalence and frequency of incontinence has been found in surgical and behavioral weight reduction interventions (Table 1). 14,15

Surgical weight loss
In observational studies, severely obese women (.45 kg above ideal weight) with incontinence who had dramatic weight loss after bariatric surgery (45-50 kg) had significant improvement in urinary incontinence. 32,67,68 In one study (n = 138), the prevalence of stress urinary incontinence decreased from 61% at baseline to 12% (P, 0.001) after stabilization of weight over 2-5 years, 32 and in a second study (n = 101), the prevalence of any incontinence decreased from 67% at baseline to 37% at 12 months (P, 0.001). 31 In another surgical cohort undergoing bariatric surgery, the prevalence of pelvic floor disorder symptoms including urinary incontinence improved from 87% before surgery to 65% after surgery. 35 In a morbidly obese cohort undergoing bariatric surgery with an average weight loss of 49 kg, there was a significant improvement in stress incontinence (P, 0.001), frequency and leakage of any degree, and overall quality of life subsequent to surgery. 69 In a cohort of 253 morbidly obese patients undergoing laparoscopic sleeve gastrectomy, stress urinary incontinence was reported preoperatively in 60 (32%) females, and complete resolution or improvement was reported in 54 (90%) patients. 70 Statistically significant changes have also been observed in urodynamic parameters, 68,71 frequency of incontinence episodes, and the need to use absorptive pads. 67 Behavioral weight loss decreased frequency of urinary incontinence episodes has also been observed following enrollment in behavioral weight loss programs, including very low calorie liquid diet and intensive lifestyle diet and exercise interventions. [71][72][73][74] In a small prospective cohort study of overweight and obese incontinent women enrolled in very low calorie liquid diet weight reduction programs, six of six women achieving a weight loss of $5% had at least a 50% reduction in frequency of urinary incontinence compared with one of four women with ,5% weight loss (P = 0.03). 71 A randomized trial of a 3-month, very low calorie liquid diet program compared with no intervention (n = 42) found greater weight loss among women randomized to the diet interventioncompared with controls (14 kg vs 0 kg) and a greater decrease in weekly frequency of incontinence episodes from baseline (60% vs 15%; P, 0.001), with decreases observed in both stress (P = 0.003) and urge (P = 0.03) incontinent episodes. 72 The weight and urinary incontinence decreases were maintained for 6 months.
Overweight prediabetic women enrolled in the diabetes Prevention Program (n = 1957) were randomized to intensive lifestyle therapy, metformin, or placebo with standard lifestyle advice. 73 At almost 3 years of follow-up, the prevalence of total weekly incontinence was lower among women in the intensive lifestyle group (38%) than those randomized to metformin (48%) or placebo (46%; P, 0.001). This difference was most apparent among women with stress incontinence (31% for intensive lifestyle group vs 40% for metformin vs 37% for placebo, P = 0.006). Change in weight accounted for almost all of the incontinence effect explained (35%), with change in exercise and incident diabetes each explaining only 5%.   In a prospective longitudinal study of 64 obese women with urodynamic stress urinary incontinence participating in a low calorie diet and exercise program with addition of orlistat, the antiobesity drug, offered to those who did not achieve a target loss of 5%-10%, weight loss of at least 5% was associated with significant reduction in pad test loss (median difference, 19 g; 95% CI: 13-28 g; P , 0.001). There was also a clinical and statistically significant improvement in quality of life measures. 75 The first large randomized trial on the effect of weight reduction on urinary incontinence included 338 overweight and obese women with at least ten urinary incontinence episodes per week randomized to an intensive 6-month weight loss program (diet, exercise, and behavior modification, n = 226) or to a structured education program (n = 112). 74 After 6 months, women in the intervention group achieved a mean weight loss of 8% compared with 2% in the control group (P , 0.0001), and the mean number of weekly incontinence episodes decreased by 47% in the intervention group compared with 28% in the control group (P = 0.01). As compared with the control group, the intervention group had a greater decrease in the frequency of stress incontinence episodes (P = 0.02), but not of urge incontinence episodes (P = 0.14). At 12 months, the intervention group reported a greater percent reduction in weekly stress urinary incontinence episodes (65% vs 47%, P , 0.001) and a greater proportion achieved at least a 70% decrease in weekly total and stress urinary incontinence episodes compared with controls. By 18 months, a greater proportion of women in the intervention group had at least a 70% improvement in urge incontinence episodes, but there were no significant differences between the groups for stress or total urinary incontinence. The intervention group also reported greater satisfaction with changes in urinary incontinence than the control group at 6, 12, and 18 months. 76

Mechanism of the obesityincontinence association
While the mechanism of the obesity-urinary incontinence association is unknown, it is theorized that excess body weight increases abdominal pressure, which in turn increases bladder pressure and urethral mobility, leading to stress urinary incontinence, and also exacerbates detrusor instability and overactive bladder. 67,72 Although a mechanical mechanism has been proposed for stress urinary incontinence in overweight and obese women, an inflammatory response in the urinary bladder has been proposed for overactive bladder. Elevated levels of urine biomarkers involved in inflammation and tissue repair have suggested a role for inflammation in overactive bladder. 77 Obesity induced by diet has also been shown to be Open Access Journal of Urology 2011:3 submit your manuscript | www.dovepress.com

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Weight loss and urinary incontinence in women associated with macrophage infiltration into adipose tissue, 78 a process which has been proposed to affect adipocytes surrounding the human bladder, leading to inflammation and overactive bladder symptoms. 79 The underlying mechanism may also be related to lower levels of circulating ghrelin levels associated with obesity that adversely affect urethral support and detrusor contractility. [79][80][81] Comorbid diabetes mellitus, closely linked to obesity, is also a risk factor for both stress and urge urinary incontinence in obese women; 14,30 the microvascular compromise induced by diabetes in obese women may adversely affect the continence mechanism or bladder "sensitivity". 79 Additionally, obesity, like pregnancy, may cause chronic strain, stretching and weakening of the muscles, nerves, and other structures of the pelvic floor that may lead to dysfunction of the continence mechanism, and place obese women at risk for incontinence. 82,83 Strong associations between BMI and intra-abdominal pressure (Pearson's coefficient correlation 0.76) and intravesical pressure (Pearson's coefficient correlation 0.71) have been observed. 84 In addition, weight loss is associated with changes in urodynamic parameters. Following large, surgically induced weight loss, statistically significant changes have been reported in urodynamic parameters, including decreased intravesical pressure, magnitude of bladder pressure increases with coughing, bladder-to-urethra pressure transmission with cough, and urethral axial mobility, 67,68 supporting the theory of increased abdominal pressure. With moderate weight loss (13% of baseline weight), significant correlations between weight change and decreased initial intravesical pressure (Spearman's r = 0.52, P = 0.01), decreased intravesical pressure at maximum capacity (r = 0.62, P = 0.001) and increased Valsalva leak point pressure (r = 0.57, P = 0.03) have been observed. 72 In a study aimed at describing the urodynamic characteristics of overweight and obese women with urinary incontinence participating in the Program to Reduce Incontinence by diet and Exercise (PRIdE), intra-abdominal pressure at maximum cystometric capacity increased 0.4 cm H 2 O per kg/m 2 unit of BMI and 0.4 cm H 2 O per 2 cm increase in abdominal circumference, and intravesical pressure at maximum cystometric capacity increased 0.4 cm H 2 O per 2-cm increase in abdominal circumference, but was not associated with BMI. 85

Patient-focused perspectives
Urinary incontinence has been associated with a profound adverse effect on overall and health-related quality of life, 86,87 a 20%-30% increased risk of falls and fractures, 88,89 and dramatic limitations in daily functioning. 2,4,5,[90][91][92][93] In a systematic review of the literature on quality of life among women with urinary incontinence, factors influencing quality of life were age, severity of urinary incontinence, type of urinary incontinence, frequency of urinary incontinence episodes, body weight, stress, and help-seeking behavior. 91 In a crosssectional study of 5530 eligible respondents to a mail survey, one of the strongest predictors of urinary incontinence was obesity, and urinary incontinence had a stronger influence on quality of life than diabetes, cancer, and arthritis. 94 Although there are many studies quantifying the effect of incontinence on general and incontinence-specific quality of life using instruments like the Short Form (SF-36) Health Survey 95 and Incontinence Impact Questionnaire, 96 respectively, there are few data on the impact of urinary incontinence on health-related quality of life measured by health utilities instruments, an important outcome for cost-utility analyses. Incontinence, Alzheimer's disease, and stroke are self-assessed as the three chronic health conditions that most adversely affect women's health-related quality of life. 6,97,98 In addition, obesity itself is associated with increased risk for coronary heart disease, hypertension, diabetes, cancer, dyslipidemia, stroke, liver or gallbladder disease, sleep apnea and respiratory disease, osteoarthritis, and depression. 9,99 Thus, women who are both overweight and incontinent are at tremendous risk for negative health outcomes and impaired quality of life.
In the PRIdE study, 74 several patient-focused perspectives were assessed. Women in the weight loss group perceived greater improvement in the frequency of their urinary incontinence, lower volume of urine lost, incontinence as a less of a problem, and higher satisfaction with the change in their incontinence at 6 months compared with women in the control group (P , 0.001) at 6 months 74 and 18 months. 76 Therefore, weight loss, a treatment approach that can impact both incontinence and obesity, is an exciting new treatment direction for this population and has tremendous implications for general and health-related quality of life.

Conclusion
Epidemiological studies demonstrate that obesity is a strong, independent, and modifiable risk factor for prevalent and incident urinary incontinence. There is a clear doseresponse effect of weight on prevalent and incident urinary incontinence. There appears to be a stronger association between increasing weight and prevalent and incident stress incontinence (including mixed incontinence) than for urge incontinence and overactive bladder syndrome. However, the precise mechanism of the association between obesity and incontinence is unknown, and additional neurophysiologic and urodynamic studies are needed to define better the obesity-urinary incontinence relationship.
Weight loss studies indicate that both surgical and nonsurgical weight loss leads to significant improvements in urinary incontinence symptoms. data support that weight loss of 5%-10% has an efficacy similar to that of other nonsurgical urinary incontinence treatments and should be strongly considered as a first-line therapy for incontinence. In addition, moderate weight reduction is associated with extensive health improvements.

Future directions
High priorities for future research include well designed observational studies and intervention trials to examine the effectiveness of weight loss for urinary incontinence in a general population of overweight and obese women with urinary incontinence; assess the comparative effectiveness of standard surgical, pharmacological, and behavioral urinary incontinence treatments in overweight and obese women; evaluate if healthier lifestyle choices, such as weight control and physical activity, are effective to prevent the onset or worsening of urinary incontinence in women; explore the mechanisms of how weight affects urinary incontinence and weight loss improves urinary incontinence; and, examine the role of adipocytokines, inflammation or other biologically active substances in the weight-urinary incontinence association. In addition, measures of urinary incontinence could be included in studies of weight loss and behavioral/lifestyle interventions to document further the effect of these interventions on urinary incontinence, better characterize women likely to benefit from weight loss, and determine if urinary incontinence improvements can be sustained with long-term weight reduction.

Disclosure
The authors report no conflicts of interest in this work.

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