Obesity, incontinence, and pelvic floor dysfunction

Urinary incontinence (UI) is a common disorder that affects approximately 25% of the general population according to large epidemiological studies.

Several factors have been implicated in UI, including parity, operative vaginal delivery, length of labour, obesity, chronic cough, depression, anxiety, poor health status, lower urinary tract symptoms, previous hysterectomy, and smoking.

UI is a cause of significant morbidity and cost, estimated at over £500 million, representing 1% of the healthcare budget, in the United Kingdom, €400 billion in Europe, and between $25 and $50 billion in the United States.

Data related to quality of life (QoL) show that the impact of the disorder can be detrimental irrespective of the patients’ age. Specifically, patients with UI suffer from depression, anxiety, and sexual dysfunction. The symptomatology is worse when obesity is also present as women with a body mass index (BMI) greater than 30 kg/m ² tend to have more severe symptoms.

Norwegian EPICONT (Epidemiology of Incontinence in the County of Nord-Trøndelag) study, which included 34,755 women, researchers observed that obesity had a significant impact on UI (stress, urgency, and mixed).

It has also been estimated that 11% of the global population suffers from overactive bladder (OAB) and 8% from UI.

Known risk factors for UI include parity, vaginal childbirth, large babies, perineal trauma, operative delivery, increasing maternal age, prior hysterectomy, and BMI, which is another compounding factor.

A study has also shown that with each increase in BMI unit, the odds ratio (OR) of developing UI increases by 1.6 and women with BMI that exceeds 35 kg/m ² have a prevalence that peeks at 67.3%.

A recent meta-analysis of prospective cohort studies assessed the relationship between overweight/obesity and the risk of UI in young and middle-aged women; the risk of developing UI increased by about a third in women in the overweight category (35%) and nearly doubled in women with obesity (95%).

The effect of age on the prevalence of incontinence becomes minimal after the completion of the fifth decade of life; however, the severity of symptoms becomes more pronounced after 70 years of age. Several factors contribute to this, including chronic ischemia of the lower urinary tract as well as the higher prevalence of abdominal obesity.

BMI correlates with intra-abdominal pressure, which increases intravesical pressure and exerts increased force on the pelvic floor, hence increasing the risk for stress urinary incontinence (SUI). Furthermore, increased intra-abdominal pressure can lead to the weakening of the pelvic floor innervations and musculature.

Chronically increased BMI is also associated with an elevated risk of UI in later life. Symptom severity also appears to worsen with the duration of increased BMI status, again confirming the detrimental effect of obesity on continence.

Functional disability and mobility problems often accompany gross obesity and are further risk factors for UI.

In women, an increase in adiposity is generally associated with a nearly linear increase in over active bladder (OAB) prevalence.

This contrasts with men, in whom as adiposity increases, the prevalence of OAB decreases to a certain point (BMI 27.5 kg/m ² ), after which as adiposity increases, the OAB prevalence increases again.

In women, this relationship has been attributed to biomechanical (and neuroendocrine) factors, whereas men, who have greater pelvic floor strength, may be less susceptible to these forces with fewest symptoms in the overweight range.

The aetiology and pathophysiology of idiopathic overactive bladder is poorly understood even in the general population; hence, no clear mechanism of the association between an overactive bladder and obesity is available.

The systemic inflammatory state and oxidative stress associated with visceral obesity might play a role in development of OAB. Administration of an antioxidant agent has shown positive effects on LUTS in obese mice.

A large randomised trial investigating the impact of a 6-month weight-loss program on outcomes of UI included 338 overweight and obese women with at least 10 UI episodes per week. This study found that weight reduction in the intervention group was approximately 8.0 kg (compared to1.5 kg in the control group), and this was accompanied by a significant reduction in incontinence episodes at 6 months (47% vs 28%). The difference was significant, however, only for cases with stress UI.

Outcomes concerning the impact of bariatric surgery on UI have shown the improvement or resolution of UI in approximately 55% of cases. Stress UI was less likely to be treated (47% of cases) compared to urgency UI (53% of cases). Worsening and new onset UI was observed in approximately 3% of cases.

Another study reporting on the impact of bariatric surgery in women with UI showed that incontinence-specific QoL scores were improved by 14%, while the proportion of women who were cured from any type of UI reached 58%.

There is a reported 73% reduction in overactive bladder symptoms in patients after surgically induced weight loss compared to their baseline symptoms. A similar reduction in distressing overactive bladder symptoms has been described in studies with nonsurgical weight loss.

Conservative treatment of stress incontinence comprises pelvic floor exercises, supervised pelvic floor physiotherapy, electrical stimulation of pelvic floor muscles, and use of duloxetine.

Duloxetine was reported to be a useful alternative in obese patients with a good response in initial studies and has been described to have antiobesity and antibinge-eating properties, along with its known antidepressant effect in animal studies.

The dual effect of this drug may have a favourable impact on SUI in these patients by a variety of mechanisms including facilitation of weight loss.