The study was cross-sectional in a small town, Brielle, in the Netherlands. Brielle was chosen because it has a homogenic population, where all women are registered in one of the nine general practices. All women aged 45 to 85 years registered on the patients lists of eight out of nine general practices were invited to enrol in the study, which is 95% of the women in this age group. The women were sent information about the study and informed that they could enrol by filling out an informed consent form. All women who consented were asked to complete a self-report questionnaire. Non-responders received a reminder 8 weeks later that contained the same questionnaire. To check for selection bias, permanent non-responders were invited to complete a short questionnaire that comprised five questions about age, parity, presence of stress urinary incontinence (yes/no), faecal incontinence (yes/no) and feeling of vaginal bulging (yes/no). To encourage a high response to the questionnaire, we used envelopes with the name and logo of the Erasmus University, coloured paper and stamped addressed return envelopes.
Three options were possible: women refused to participate in the study, women filled out only the questionnaire and women filled out the questionnaire and underwent vaginal examination. For the purpose of this study, data on vaginal examination are not used. The relation between symptoms and signs of vagina prolapse has been extensively described in an earlier study [6
]. A flowchart of the study design is presented in Fig. . In this study, all women who answered the questionnaires are included.
The self-reported questionnaire used for this study are a composite of internationally well-known questionnaires that have been validated for the Dutch language. It contains, amongst others, disease-specific questions from the validated Dutch translation of the Urinary Distress Inventory(UDI) [7
] next to other questionnaires and items which were not used for the present study [6
Women rated the amount of bother of various symptom on a 5-point Likert scale, from 0 (no complaints at all) to 4 (very serious complaints). In addition, questions about ethnicity, parity, POP symptoms during pregnancy, family history, menopausal status, hormone replacement therapy (HRT), previous pelvic floor surgery, educational level, smoking and heavy physical work were also included.
The Medical Ethics Research Committee (METC) of the Erasmus MC in Rotterdam, the Netherlands, approved this study.
All symptoms were dichotomized as present or absent based on responses to each symptom and degree of bother with these symptoms. Women who denied the presence of a specific symptom as well as women who answered confirmative on a specific question but answered not to be bothered by it were considered as negative (absent) while women who indicated that they were little to severe bothered were considered as positive (present). The item of POP symptoms is merged from women who reported either seeing and/or feeling vaginal bulging. For the item any OAB symptoms, women who had urgency and/or frequency and/or urge incontinence symptoms were included (see Fig. ).
Any OAB symptoms in relation to urgency, frequency and urge incontinence
Data are presented as number of women (percentage), mean (standard deviation) or median (range) as appropriate. Chi-square test was used to compare the difference between the women with- versus without POP symptoms.
Logistic regression was used for the univariate and multivariate analysis. For logistic regression, the backward elimination procedure was used. Variables with a P
0.3 in univariate analysis were included in the multivariate analysis. We presented the odds ratio (OR) and 95% CI for each of the OAB symptoms. The level of significance was set at an alpha value of 0.05. All data were entered and analysed in a SPSS 15.0 database for Windows (SPSS, Inc., Chicago, IL).