Many authors have compared the relationship between overactive bladder (OAB) and obesity. However, there is a lack of studies investigating the impact of being overweight and body fat distribution as risk factors for OAB on various aspects of quality of life (QoL). Being overweight is the precursor to obesity. It is referred to as its first stage and brings an increased risk of health complications. The aim of this study was to compare body composition in overweight women with OAB compared to women without OAB, and to determine the severity of the symptoms of OAB, as well as to investigate the impact of OAB on QoL.

We determined the sample number according to prevalence of OAB according to the following estimation: n = Z2P(1 - P)/d2, where Z = 1.96 (95% confidence level), P = 0.16 for expected OAB prevalence of 16% and d = 0.05 (10% confidence interval [CI] width). Based on this calculation, the minimum number was set at n = 195 participants. The research population comprised a convenient sample of university students. The women were randomly selected from two universities. In all, 7943 women completed a screening questionnaire with age, height, and weight information. Calculation of body mass index (BMI = m/h2, where m = body weight in kg and h = body height in m). All overweight women (BMI 25-29) were enrolled, with a total number of 1932. Of this number, every 7th woman was randomly selected, so a total of 276 women were examined.
The inclusion criteria were as follows: women aged 18-35 years; BMI 25-29.
The exclusion criteria were: stress urinary incontinence (SUI), surgery for gynaecological or urological diseases, infection of the urinary tract, oncological or neurogenic disease of the lower urinary tract, incomplete questionnaires, and refusal to participate in the study.
We used the Voiding Diary, the Overactive Bladder Questionnaire (OAB-q), and the Incontinence Quality of Life (I-QOL) scale. Body composition was measured using direct segmental multi-frequency bioelectrical impedance analysis with body composition analyser, with assessment of: skeletal muscle mass (kg), body fat mass (kg), body fat percentage (%), visceral fat area (cm2/level), and waist to hip ratio. Participants had OAB if they had urinary urgency, voiding eight or more times per day, two or more times per night, with or without urgency urinary incontinence.

The sample consisted of 206 out of 276 women with an average age of 30.6±20.4 years, the response rate was 74.6%. Out of these, 102 were women with OAB and 104 without OAB. The voiding diary and OAB-q results confirmed OAB in 102 women. There was no significant difference in BMI between groups. The body composition analysis showed significant differences in body fat percentage, visceral fat area, and waist to hip ratio with significantly higher values in the OAB group (p < 0.01), skeletal muscle mass (kg), however, was significantly higher in the group without  OAB (p < 0.01). Recorded I-QOL scores showed significantly worse parameters in total score in the OAB group (p < 0.001). Women with fat percentage above 28% have a 1.95 times greater chance of developing OAB. Odds ratio [OR] = 1.95, (95% CI: 1.09-3.52, p = 0.024). The results are summarized in Table 1.
Table 1. Statistical comparison of monitored parameters in women with and without OAB

We evaluated OAB by means of voiding diary and OAB-q questionnaire. Significantly higher values were found in the OAB group for body fat percentage, visceral fat area, and waist to hip ratio with comparable BMI, confirming overweight by means of Body Composition Analysis. However, skeletal muscle mass was significantly higher in the non-OAB group.OAB has a negative impact on QoL. Data from two studies indicate, that measures of central adiposity are also correlated with urgency urinary incontinence 1, 2.

Higher body fat percentage, visceral fat area, and waist to hip ratio were significantly higher in overweight women with OAB, though comparable BMI. Women with fat percentage more than 28 % have 1.95 greater likelihood of developing OAB.

The Journal of urology, 2011, 185(3), 955-963.
Journal of Korean Medical Science, 2011, 26(2), 250-257.