Impact of overweight and obesity on women with urinary incontinence: pilot study


 IntroductionTo assess whether obesity has a greater impact than overweight on urinary incontinence severity, pelvic floor muscle function, and quality of life in women with urinary incontinence. MethodsA pilot cross-sectional study using a convenience sample. Twenty-six volunteers were evaluated and divided into: Overweight Group (n=11) with BMI (body mass index) between 25.0-29.9kg/m²; Obesity Group (n=15) BMI≥30.0kg/m². The volunteers performed the urogynecological evaluation, Incontinence Severity Index (ISI), the King’s Health Questionnaire (KHQ), 1-hour pad test and evaluation of pelvic floor muscle function. Statistical analysis: Shapiro–Wilk test and the Mann-Whitney test for intergroup analysis. The significance level: p≤0.05. ResultsThe average age was 61.09(12.51) in the Overweight Group and 55.93(9.03) years in the Obesity Group. The Overweight Group presented better fast fiber contraction (p=0.03) of the pelvic floor muscle. There were no differences in the ISI and quality of life between the groups. ConclusionsThere was no difference in the impact caused by being overweight or obese in relation to urinary incontinence severity, pelvic floor muscle function and quality of life, except for fast fiber contraction in which Overweight Group showed better results.


Introduction
Obesity is one of the biggest public health problems in the world, affecting around 300 million people 1 . The increase in obesity in Brazil is worrying because it is a risk factor for diseases such as hypertension, diabetes 2 and pelvic oor muscle dysfunction (PFMD) 3 . Subak (2009) 4 found that a 5-unit increase in body mass index (BMI) increases the risk of urinary incontinente (UI) by 20-70% 4,5 .
The pathophysiological explanation for UI development in women with obesity is due to the increase in intra-abdominal pressure (IAP) caused by an elevated BMI which can chronically overload the pelvic oor muscles (PFM) 6,7 . In addition, obesity can cause neurogenic diseases such as disc herniation, contributing to developing PFMD and increasing the risk of UI in women 8 .
As stated above, various studies [3][4][5][6][7] have shown the relationship of obesity with the presence of PFMD, especially UI 3,4,6,7 . However, there are few studies in the literature evaluating whether overweight women have the same characteristics in PFM function and UI severity as obese women. Therefore, it is necessary to assess whether obesity has a greater impact than being overweight on UI severity, PFM function, and quality of life (QL) of women with UI.

Methods
A pilot cross-sectional study following the methodological guidelines of STROBE, using a convenience sample conducted from April/2016 to June/2017. The inclusion criteria were: UI; age ≥ 35 years; and BMI ≥ 25Kg/m². The exclusion criteria included: latex allergy; urinary or vaginal infection; pelvic organ prolapse; cognitive and neurological disorders; uncontrolled hypertension; inability to perform the assessment; hormone replacement therapy [9][10][11] .
The research was conducted in accordance with the World Medical Association's Code of Ethics (Declaration of Helsinki), and Resolution 466/2012. The study was approved by the Research Ethics Committee: 1.475.807. All procedures were performed after being explained about the study, and signing the free and informed consent form. between 25.0-29.9 kg/m², and the Obese Group (OG) with BMI ≥ 30.0 kg/m² 12 .
Women were submitted to anamnesis with gynecological, obstetric and urological information, the Incontinence Severity Index (ISI), and the King's Health Questionnaire (KHQ). The physical assessment was performed by the 1-hour pad test and evaluation of PFM function.
The ISI questionnaire 13 is a brief instrument, translated and validated into Brazilian Portuguese 14 . The nal score is obtained by multiplying the scores of the rst (Frequency Domain) with the second (Amount Domain) question, being classi ed as: mild: 1-2; moderate: 3-6; severe: 8-9; very serious: 10-12 13 16,17 . The nal score ranges from 0 to 100, with higher scores indicating worse QL 17 .
The 1-hour pad test was performed to measure urinary loss and in according with the protocol of Abrams et al 18 .
The evaluation of PFM function, the PERFECT scheme and Modi ed Oxford Scale were used 19 . The volunteers were in the supine position with their knees exed and their hips abducted. The evaluator introduced two ngers up to one-third of the vaginal canal and instructed the volunteers to perform a maximal PFM contraction.
Statistical analysis was performed using the Statistical software 7.0 program (StatSoft Inc., Tulsa, United States). The Shapiro-Wilk test identi ed non-parametric distribution. The Mann-Whitney test was used for intergroup analysis. The signi cance level: p ≤ 0.05.

Results
Twenty-six (26) women were evaluated, 11 in OWG and 15 in OG. The average age of OWG was 61.09 ± 12.51 and OG 55.93 ± 9.03 years old and with homogeneous distribution. Furthermore, 67% of OWG and 80% of OG were married. The obstetric variables did not differ (Table 1). severe or very severe, while 60.0% in the OG presented moderate severity and 33.3% severe. There was no statistical difference between the groups ( Table 2).
The OWG presented better fast ber contraction (p = 0.03) of the PFM than the OG. No signi cant difference was found in the other PERFECT steps and in the 1-hour pad test (Table 2). There was no signi cant difference between groups in the QL (Table 3). However, both groups had a negative impact on the general health perception and UI impact domains of KHQ.

Discussion
No signi cant differences were found between groups of overweight and obese women regarding the type and severity of UI, on the 1-hour pad test and in the steps power, endurance, and repetition for PERFECT; however, it was found that the OWG obtained a better PFM contraction of fast bers.
Obesity may result in increased IAP, compromising PFM integrity, damaging nerves, muscles, and connective tissue, resulting in urethral hypermobility 20 . Furthermore, obesity causes descent and rotation of the bladder neck and part of the urethra, changing the pressure gradient and generating urine leakage 20 , justifying the most frequent type of UI was that the SUI in both groups.
The urge-incontinence may happen in obese women due to a reduced amount of the hormone ghrelin 20 . This hormone inhibits the detrusor muscle contractile response, bringing adverse effects on urinary control 20 . The decreased ghrelin may result in increased detrusor muscle contractile response in obese women, causing urgency and urge incontinence.
The prevalence of UI does not only occur in obese women. According to the study 21 , overweight women are 2.7 times more likely to have UI than those with normal weight. This study may justify the fact that the severity of UI, the pad test, the contraction capacity and resistance of PFM, and the QL in the present study did not present a signi cant difference between obese and overweight women.
Other studies have veri ed the association of the severity of UI with PFM strength, where lower force would result in a urethral closure de cit and higher UI severity, and may be associated with poorer QL 22,23 . The majority of the women in the present study had moderate or severe UI in the OWG and moderate or very severe UI in the OG. In both groups this had a negative impact on the QL, highlighting this possible association between the severity of UI and the QL.
The OWG presented better contraction of the PFM fast bers than the OG, corroborating the fact that weight gain is considered a risk factor for SUI, in which the fast bers do not contract effectively 8,24 . Another's studies comparing overweight and obese individuals with lean subjects identi ed a reduction in the percentage of oxidative muscle bers and increase in glycolytic 25 , but another study showed no change 26 .
These controversial results which are presented in the literature may be in uenced by genetic and ethnic factors 25,26 which also in uence the function of PFM, and so there is a limitation in justifying the obtained results. This is because our results indicate a worse contraction capacity of fast bers in the OG, which besides being associated with increased IAP may also have other in uencing factors which have not been evaluated.

Conclusion
Although the study presents relevant ndings, the results should be carefully analyzed, as this is a pilot study with a small sample size, making it necessary to conduct more research with a larger sample number. Future studies may include in their analysis questionnaires that evaluate other types of PFMD and satisfaction with self-image.
From the obtained results, it can be concluded that there is no difference in the impact caused by being overweight or obese in relation to the severity of UI. The contraction and resistance capacity of PFM and the QL presented similar results between the groups, but the OWG presented better contraction of the fast bers than the OG; thus, it can be said that obese women present a decrease in the contraction capacity of fast bers of the PFM, which may worse the UI severity.

Consent for publication
All participants were informed about the steps of the research and the objective of the study, and agreed to sign the consent form.

Availability of data and materials
The datasets during and/or analysed during the current study available from the corresponding author on reasonable request.