What’s known on the subject? and What does the study add?

Overactive bladder is a condition that affects quality of lif and daily social, emotional and physical activities of patients. This study aims to evaluate the prevalence and possible risk factors of overactive bladder symptoms among women living in a western city of Turkiye, İzmir.

Introduction

Overactive bladder (OAB) is a condition that affects health-related quality of life and daily social, emotional and physical activities of patients (1). The International Continence Society (ICS) defines OAB as urgency, with or without urgency urinary incontinence (UUI), usually with frequency and nocturia (2). In several population-based studies, the prevalence of OAB symptoms (OABS) has been reported to be between 11% and 32.6% (3,4,5). Although patients with OABS (with or without UUI) have-high level depression, sexual problems, and distress in daily life, most patients do not consult a doctor for any treatment and continue to suffer from OABS (3).

The underlying causes of the pathophysiology of OABS have not been fully established. For this reason, many studies have been conducted in many countries to establish the causes and risk factors for OABS in their populations. Aging, chronic diseases, such as diabetes mellitus (DM) and hypertension, obesity, socioeconomic status, being married and childbirth have been shown to be associated with OABS (5,6,7,8,9,10).

There are several studies in the literature comparing the risk factors for OABS, lower urinary tract symptoms and urinary incontinence (UI) in the Turkish population and showing the effect of these conditions on the quality of life of patients (11,12,13). In this study, we aimed to evaluate the prevalence and possible risk factors for OABS and severity of OABS among adult women living in a western city of Turkiye, İzmir, with face-to-face interviews by experienced urologists.

Materials and Methods

This study was approved by the Ethics Committee of Dokuz Eylül University with number 2016/05-35. The cohort included all women over 18 years of age who accepted to participate in the study and completed the informed consent form on a weekend for International Women’s Day Campaign at İzmir International Fair. The questionnaire used in the study was completed by participants during face-to-face interviews with urologists. Participants who were unable to respond to questionnaire due to cognitive disability and who had dementia or any neurological disease were excluded from the study. Also women having symptoms of cystitis, such as dysuria and fever, and those receiving antibiotic therapy for urinary tract infections were excluded from the study.

The questionnaire consisted of 2 parts. Socioeconomic and demographic features such as age, occupation, level of education, parity, marital status, and physician referral status, as well as systemic diseases such as hypertension, DM, coronary artery disease, chronic obstructive pulmonary disease, etc. and previous operation history were evaluated in the first part; the validated International Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF) (14) and Overactive Bladder Symptom Score (OABSS) (15) were administered in all participants in the second part. Definitions for OABS and UI types were used according to the standard definitions of the ICS (2). The 8-item Overactive Bladder Questionnaire (OAB-V8) consists of 8 questions each of which can be graded by the patient within a scale of never (0); few (1); sometimes (2); quite a few (3); usually (4); and always (5). Thus, the total score ranges from a minimum of 0 to a maximum of 40. A total score of 8 or greater on the OABSS indicates high risk for OAB (15). Therefore, for subsequent analysis, we classified women with an OABSS greater than 8 as having OABS (group 1) and women with an OABSS less than 8 as having no OABS (group 2). The participants with or without OABS were evaluated in terms of risk factors such as age, comorbidities, parity, presence or absence of incontinence, status of doctor consultation, education level, marital status and total ICIQ-SF score and OABSS. The participants were also divided into 3 groups according to age distributions and each group was evaluated in terms of OABS status.

Statistical Analysis

Categorical variables were compared with chi-square test and continuous variables were compared with independent samples t-test. Multivariate regression analysis was used to define the potential risk factors for OAB. The results were expressed as adjusted odds ratio with 95% confidence interval. Statistical analyses were performed with Statistical Package of Social Sciences version 22.0 (SPSS, Chicago, Illinois, United States of America) and a p value of less than 0.05 was considered statistically significant.

Results

The mean age of 719 women participating in the study was 51.2±11.1 years. Socioeconomic and demographic characteristics, comorbidities, UI status and OABS of the participants are presented in Table 1. The prevalence of OABS was 42.8% and the prevalence of UI was 50.3% in the study. In the participants with OABS, the prevalence of OABS with UI (OAB_wet) was 69.2% and the prevalence of OABS without UI (OAB_dry) was 30.8%. In this study, the incidence of frequency, nocturia, UUI was found to be 72.3%, 61.8%, 42.7% and 37.7%, respectively. In our study, 86.7% of participants with OABS consulted a doctor previously, whereas 13.3% of participants did not consult a doctor (p<0.001).

In this study, we showed using univariate analysis that the most significant potential risk factors associated with OABS were age (p<0.001), DM (p<0.001), hypertension (p<0.001), parity (p<0.001), education level (p=0.002), marital status (p<0.001) and obesity (p<0.001) (Table 2). However, there were no statistically significant relationship between OABS and the other possible risk factors (Table 2). Patients with OABS had more frequent UI and nocturia than patients without OABS (Table 3). In addition, there were statistically significant association and correlation between OABS severity and presence of nocturia and UI types (r=0.363, p<0.001, r=0.568, p<0.001). When we examined the relationship of age with OABS severity and storage symptoms, we found a statistically significant difference between age groups in terms of OABS severity and storage symptoms especially nocturia and UI (Table 4). Body mass index (BMI), total OABSS and frequency of nocturia increased with age (Table 4).

According to our results, major risk factors for OABS were DM, hypertension, obesity, marital status and low level of education in multivariate logistic regression analysis (Table 5). When we evaluated univariate and multivariate analyses, we found that some variables showed different relationships with OABS. There was a statistically significant difference in age and parity between participants with and without OABS (p<0.001) (Table 2), whereas the statistical significance was not observed in multivariate analysis (Table 5).

Discussion

OAB is a chronic disease and it is defined by the ICS as urgency, with or without UUI, usually with frequency and nocturia (2). The present study was designed as a community-based survey to evaluate the risk factors and the prevalence of OABS in women, living in İzmir, a western city of Turkiye. In our study population, the prevalence of OABS was 42.8%. According to age groups, the prevalence of OAB was 27.7% in those below 40 years of age, 44.9% in those aged 40-60 years, and 49.2% in women above 60 years of age. The European Prospective Investigation into Cancer and Nutrition study showed that the global prevalence of OABS was 11.8% and 51% of men and 56% of women aged 40-59 years suffered from storage symptoms (3). In two different studies conducted in Japanese women, the prevalence of OABS was ranged between 8.1% and %11 (6,7). Kim et al. (8) reported that the prevalence of OABS was approximately 5.2% among adult Korean women. The prevalence of OABS was found to be 6.0% in the Chinese population (9). The differences between the prevalence rates in our study and other studies may be related to inclusion criteria, such as age, race, systemic diseases, definition variety of OABS, design of questionnaires and survey methods. Most of these studies were planned at outpatient clinics and the participants were interviewed via telephone or internet and the OABSS questionnaire was not used for determination of OABS. Although reaching a wider range of participants in surveys conducted via telephone and internet, the disadvantage of such studies is the time allocated for participation is limited and attendees’ participation in the questionnaires is low. For these reasons, it may be more difficult to evaluate the actual situation of participants during telephone and internet interviews than in face-to-face interviews. This may lead to differences in OABS prevalence. Unlike previous studies, according to the best of our knowledge, our study was the first community-based study designed as face-to-face interviews and the OABSS was filled by experienced urologists.

There are few studies evaluating the prevalence of OABS in Turkiye. Zumrutbas et al. (11) reported that the prevalence of storage symptoms was 64.1% in women in a western city of Turkiye, Denizli. In our study, the prevalence of frequency, nocturia, urgency and UUI was found to be 72.3%, 61.8%, 42.7% and 37.7%, respectively.

OABS is defined by the ICS as wet and dry for more precise diagnosis of OAB and for more effective treatment. Most of studies in the literature have found different results on the prevalence of OAB_dry and OAB_wet. Wang et al. (9) showed that the prevalence of OAB_wet was 70.0% and the prevalence of OAB_dry was 30.0% among individuals with OAB. Wen et al. (10) showed that the OAB_dry-to-OAB_wet ratio was about 1:1. In present study, the prevalence of OAB_wet was 69.2% and the prevalence of OAB_dry was 30.8% in individuals with OAB and the OAB_dry--to-OAB_wet ratio was about 2.3:1. Similar to the differences in the studies of the OABS prevalence, the cause of the difference may be related to study design and age, gender and comorbid conditions of the participants involved in the study.

Many studies in the literature aimed to determine the risk factors for OABS. Possible risk factors for OABS include advanced age, obesity, hypertension, drug use, lower educational level, marital status, parity, and alcohol consumption (8,9,10). In present study, according to multiple logistic models, DM, hypertension, being married, low education level and obesity were associated risk factors for OABS.

Previous researchers have pointed to an increase in the prevalence of OABS associated with aging (3,8,9). This increase may be explained by aging processes that cause deterioration of the bladder functions due to decreased muscle and neurological activities, changes in physical status by aging and age-related factors such as menopause and systemic diseases. In this study, patients with OABS were older than those without OABS. As the age increased, frequency of OABS, especially nocturia and UI, also increased. Moreover, we found that aging-related systemic diseases such as DM, obesity and hypertension were key risk factors for OABS.

Previous studies reported that there was an association between DM and OABS (8,9,16). In addition, Kaplan et al. (17) examined the urodynamic findings in DM patients and found detrusor overactivity in 55% of patients. One of the late complications of DM is peripheral neuropathy (17). The cause of diabetic neuropathy includes impaired glucose metabolism, ischemia, superoxide-induced free radical formation, damaged axonal transport, and metabolic derangement of the Schwann cell resulting in segmental demyelination and impairment of nerve conduction (18). Therefore, peripheral neuropathy can cause detrusor overactivity and may be an important risk factor for OABS (19). Consistent with the literature, in our study, DM was a significant risk factor for OABS.

Obesity was demonstrated to be a risk factor that was significantly associated with OABS in several studies (8,9,10,20). A patient with a BMI greater than 30 kg/m² is at increased risk for the onset of OABS (20,21). Our results showed a significant association between OABS and obesity. This association can be explained by mechanical, neuroendocrine and inflammatory factors. Obesity may increase bladder pressure which, in turn, causes or increases detrusor instability and results in OABS (22). On the other hand, adipose tissue may increase autonomic nerve activity by secreted leptin hormone, especially noradrenergic sympathetic nerves, and increased sympathetic activity results in urinary frequency (23). Furthermore, obesity is associated with a chronic inflammatory response resulting in oxidative stress, increased acute phase reactants, and activation of inflammatory signaling pathways (24). Due to the increase in concentrations of interleukin (IL)-1, IL-6, and tumor necrosis factor alpha in detrusor may result in overactivity (25).

In the literature, there are few studies linking hypertension to OABS (8,26). However, there are many studies showing the relationship of OAB with hypertension and metabolic syndrome (27,28,29). Kim et al. (8) showed significant associations between OABS and hypertension. Hypertension and vascular risk factors result in increased ischemia, which leads to structural changes in the bladder (30). Moreover, when the bladder blood flow decreases because of hypertension, adenosin triphoshate and prostaglandin E2 release from the urothelium and contractions occur in the bladder (31). Therefore, hypertension and vascular risk factors can lead to OABS. Similarly to the previous study, hypertension was found to be a risk factor for OABS in this study.

Low education level and being married are the possible risk factors of OABS in women. Previous studies and our study demonstrated a clear relationship between low education level and risk of OABS (9,32). Smoking, poor hygiene and urinary tract infections may be more frequent in people with lower education levels, while those with higher education levels tend to search better health behaviors and consequently have a healthier lifestyle. However, there are conflicting results in the literature suggesting that being married was a risk factor for OABS. Similar to our results, Wang et al. (9) demonstrated that being married was a risk factor for OABS. On the contrary, Kim et al. (8) found that unmarried status was significantly related to OABS. The reason for this disparity may depend on the age, socioeconomic level, type of delivery and number of births of the participants.

Despite the considerable physical, social and psychological morbidity related with OABS, many patients do not consult healthcare professionals. OABS, especially storage problems, may embarrass patients, thus, patients may not volunteer to talk to their doctor about these complaints. Additionally, patients with OABS may believe that no effective treatment was available for OABS. Milsom et al. (33) reported that 40% of individuals with OABS did not seek medical help. Üçer et al. (34) showed that 57% of patients with OAB symptoms had not been previously admitted to hospital. In our study, this rate was found to be 13.7%.

Study Limitations

The current study has some limitations. First, we evaluated the participants on a weekend for International Women’s Day Campaign at İzmir International Fair and in a limited time, the number of participants can be considered relatively small compared to previous studies. Second, urinalysis was not performed to identify urinary tract infections. However, the OAB-V8 was filled by urologists during face-to-face interviews; patients, who complained of fever and dysuria and have recently been treated for cystitis, were identified with anamnesis and excluded from the study.

Conclusion

The prevalence of OABS in Turkish women was high and OABS affected almost half of the adult women and risk factors associated with OABS were similar to those in other countries. In accordance with the previous studies, obesity, medical comorbidities such as DM and hypertension, marital and low education were key risk factors for OABS and aging was associated with the presence of OABS and storage symptoms. According to the best of our knowledge, our study was the first community-based study designed as face-to-face interviews by experienced urologists. We assume that our study may contribute to the literature since it determines OABS prevalence and risk factors in women living in a western city of Turkiye, İzmir.

Ethics

Ethics Committee Approval: This study was approved by the Ethics Committee of Dokuz Eylül University with number 2016/05-35.

Informed Consent: All participitant completed the informed consent form.

Peer-review: Externally peer-reviewed.

Authorship Contributions

Surgical and Medical Practices: B.İ., V.Ş., O.B., Ö.D., A.E., Concept: B.İ., V.Ş., O.B., Ö.D., A.E., Design: B.İ., V.Ş., O.B., Ö.D., A.E., Data Collection or Processing: B.İ., V.Ş., Analysis or Interpretation: B.İ., V.Ş., O.B., Literature Search: B.İ., Writing: B.İ., O.B.

Conflict of Interest: No conflict of interest was declared by the authors.

Financial Disclosure: The authors declared that this study received no financial support.