Introduction

According to the International Continence Society (ICS) [1], urinary incontinence (UI) is defined as any complaint of involuntary leakage of urine. UI creates a great deal of physical, psychological, and social distress for women, as well as a substantial financial burden and a significant adverse impact on quality of life (QoL) [2, 3]. There is a wide worldwide variation in reported prevalence rates for female UI, which range from 5% to 70%. This is due to several factors including differences in the definition of UI, the age distribution of populations, research sampling methods, survey patterns, and response rates [4,5,6,7]. Prevalence estimates for UI among women in China range from 14.84% to 37.20%, based on data from Beijing, Hubei, and Hunan provinces, and a 2009 national multicentre survey showed that the prevalence among women over 20 years of age in China was 30.90% [8,9,10,11].

However, reliable data regarding female UI in Fujian Province continue to be scarce. Furthermore, the prevalence of UI in women in rural areas remains unknown, although it is possibly higher in rural settings than elsewhere due to the high frequency of childbirth in rural Chinese women, which is considered an important risk factor for the development of UI [12]. The lack of available data makes it difficult to assess the burden of UI in these settings, thus inhibiting the development of strategies by government and health authorities to assist rural women in avoiding or addressing this problem.

Hence, the aims of this study were (1) to determine the prevalence of UI among women in rural Fujian, (2) to describe the type and severity of UI and assess the impact of UI on women, (3) to analyse the risk factors associated with UI, and (4) to assess women's knowledge of UI and their willingness to seek medical care.

Methods

This study is a key component of the Female Pelvic Floor Health Management Centre Project in Fujian Province, which is administered by the Fujian Provincial Health Commission. The purpose of this project is to identify the prevalence of female pelvic floor dysfunction (FPFD), to improve the model of FPFD management, and ultimately to improve the efficacy of FPFD treatment.

Study design

The population-based cross-sectional survey was conducted between June and October 2022 in Shaxian County, a rural county in northwest Fujian. A multistage cluster random sampling was used to select women aged between 20 and 70 years to participate in the survey. Exclusion criteria included individuals diagnosed with urinary tract obstruction, urethral diverticulum or indwelling catheter, and those not clearly conscious. Pregnant women and women within the first trimester after childbirth have an increased prevalence of UI and were excluded [12]. According to the Kish-Leslie formula, N = deff × Z2× (P × [1 − P]) / E2, N is the minimum sample size required for this survey, deff refers to the design effect, Z refers to the confidence interval (CI), P refers to the expected prevalence, and E represents the permissible error. The deff was set at 4, the CI at 95%, the prevalence rate was assumed to be 25% and the permissible error was 2.5%, resulting in a minimum sample size of 1083. Therefore, our sample of 6000 women was sufficient. Shaxian County has a total of ten small towns, and the randomised selection strategy was formulated as follows: First, according to the results of the sample size calculation, an average of 600 people would be sampled from each town. The villages belonging to each town were then arranged and coded in order of the first letter of their name, with between three and five villages subsequently selected by simple random sampling to meet the sample size. Finally, all women aged 20–70 in the selected villages were invited to participate in the survey. The study received ethical approval from the Ethics Review Committee of Shaxian County General Hospital, and was conducted anonymously, with either verbal or written consent obtained from the participants prior to their participation in the survey.

Data collection

All respondents were interviewed face-to-face utilising standardised questionnaires to collect data. Since a significant proportion of rural residents were illiterate, interviewers were well trained to translate specialised technical vocabulary into easy-to-understand content for questioning. All interviewers were general practitioners (GPs) drawn from local community health centres. The questionnaire was divided into three parts, the first of which was designed to investigate women's sociodemographic characteristics and obstetric-related conditions. Body mass index (BMI) categories were defined according to the recommendations from the National Health Commission of China as follows: underweight (BMI < 18.5 kg/m2); normal (BMI 18.5–23.9 kg/m2); overweight (BMI 24–27.9 kg/m2); and obese (BMI ≥28 kg/m2) [13]. The definition established for a macrosomic baby in China is a birth weight of ≥ 4000 g [14].

The second component of the survey was designed to determine the presence and subtype of UI, as well as the frequency and severity of leakage and the impact on QoL. This element of the survey was carried out using the International Consultation on Incontinence Questionnaire–Short Form (ICIQ-SF) developed by the ICS [15]. The Chinese version of the ICIQ-SF questionnaire was proposed by Huang [16], and a pilot trial was conducted among 300 women before the study began. The ICIQ-SF consists of four sections, with options in the first three sections being assigned different scores on a total scale of 0–21, with mild, moderate, and severe UI corresponding to scores of 1–7, 8–13, and 14–21, respectively: (1) frequency of urine leakage (never: 0, once a week or less often: 1, two or three times a week: 2, once a day: 3, several times a day: 4, all the time: 5); (2) volume of urine leakage (none: 0, small amount: 2, moderate amount: 4, large amount: 6); (3) impact on life (a score of 0 means that UI has no impact on QoL, and a score of 10 means that QoL is greatly affected by UI, and the degree of impact is expressed by selecting a score between 0 and 10). The final section identifies subtypes of UI based on symptoms at the time of leakage and includes eight options: (1) never—urine does not leak; (2) leaks before you can get to the toilet; (3) leaks when you cough or sneeze; (4) leaks when you are asleep; (5) leaks when you are physically active/exercising; (6) leaks when you have finished urinating and are dressed; (7) leaks for no obvious reason; (8) leaks all the time. If the respondent selected option (1), she would be considered as not having UI. If she selected options (3) and/or (5), she would be considered as having stress UI (SUI). if she selected one or more of options (2), (4), and (6), urgency UI (UUI) would be considered. If the respondent had both SUI and UUI as described above, or chose options (7) and/or (8), then she would be identified as having mixed UI (MUI).

The third component of the questionnaire was used to investigate women's self-perception of UI and was divided into four questions, as follows: (1) Have you heard about urinary incontinence? (2) Do you think urinary incontinence is a normal part of the body's ageing process? (3) Do you think urinary incontinence can be prevented? (4) If urine leakage occurred, would you seek medical help for it?

Statistical analysis

Data were entered using EpiData version 3.0, and statistical analyses were performed utilising IBM SPSS version 20.0 software (IBM Corporation, Armonk, NY, USA). Continuous variables were expressed as mean + standard deviation or median (interquartile range, IQR) depending on whether they conformed to a normal distribution, and differences between groups were compared using the Student t-test or Kruskal–Wallis test, respectively. Categorical variables were expressed as counts (percentages), and differences between groups were compared using the chi-square test or Fisher's exact test. Multivariate logistic regression models were used to determine which factors remained independently associated with UI after adjustment for confounding factors. The relationship between sociodemographic characteristics and the self-perception of UI was also analysed, utilising multivariate logistic regression analysis. The associations are reported as odds ratios (OR) with the corresponding 95% CI. Statistical significance was set at the 5% level (P < 0.05).

Results

A total of 6000 women were selected to participate in this survey, of which 256 declined to participate and 85 were excluded for incomplete data. Ultimately, 5659 questionnaires were completed, representing a response rate of 94.32%.

Respondent characteristics

The average age of the women in this survey was 47.75 ± 11.15 years, and the average BMI was 22.41 ± 3.72 kg/m2. The mean number of deliveries among the participants was (2.51 ± 1.02), with 48.7% having experienced three or more transvaginal deliveries. The sociodemographic characteristics and obstetric history of the participants are presented in detail in Table 1.

Table 1 Sociodemographic characteristics and obstetric history of participants, and univariate analysis of factors associated with UI
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Prevalence of UI

The overall prevalence of female UI was 23.6% (95% CI 22.5–24.7). The most common type was SUI, with a prevalence of 14.0% (95% CI 13.1–14.9), followed by MUI with a prevalence of 6.1% (95% CI 5.5–6.7), and finally UUI with a prevalence of 3.5% (95% CI 3.0–3.9) (Table 2). It is notable that the overall prevalence increases with age (Fig. 1). Figure 2 presents the subtypes of incontinence for each individual age group.

Table 2 Prevalence and severity of UI
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Fig. 1
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Age-specific prevalence of UI subtypes

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Fig. 2
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Distribution of UI subtypes according to age

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The frequency and volume of urine leakage and its impact on daily life are shown in Table 3. As far as subtypes are concerned, MUI features a larger volume of urine leakage than SUI and UUI (P = 0.004), and its impact on QoL is greater than that of the other two types (P = 0.025).

Table 3 Frequency and volume of urine leakage and its impact on daily life
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Risk factors associated with UI

The univariate analysis suggested that UI was associated with several characteristics, as detailed in Table 1. These included older age, obesity, menopausal status, lower education level, lower income, a higher number of vaginal deliveries, macrosomic delivery, instrumental vaginal delivery, and a history of pelvic floor surgery. Further multivariate logistic regression analysis showed that each of these factors—with the exception of education and income level—was independently associated with increased likelihood of UI, and these covariates were highly correlated (Table 4).

Table 4 Multivariate logistic regression analysis of factors associated with UI
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Self-perception of UI

In this survey, only 24.7% of respondents stated that they had heard about UI, and this percentage decreased with age. Among respondents, 45.6% believed that UI is a normal part of the process of physical ageing, with only 17.1% believing that measures can be taken to prevent incontinence. Only 33.3% of participants would seek medical help for an incontinence problem (Table 5 and Fig. 3). A multivariate logistic regression analysis showed that older age and lower levels of education and income were strongly associated with lower awareness of UI among women (Table 6).

Table 5 Self-perception of UI in different age groups
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Fig. 3
figure 3

Self-perception of UI in different age groups

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Table 6 Association between sociodemographic factors and UI
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Discussion

This population-based cross-sectional study provides an up-to-date picture of female UI in rural China. Despite the large population in rural China, studies on the prevalence of female UI in rural areas are still rare.

The study revealed an overall prevalence of UI of 23.6% in rural women aged 20–70 years, which rises in parallel with increasing age and BMI. The prevalence of SUI, UUI, and MUI was 14.0%, 3.5%, and 6.1%, respectively. This finding is consistent with another survey conducted in Beijing, in which Ge et al. concluded that the overall prevalence of UI was 22.1%, and the prevalence of SUI, UUI, and MUI was 12.9%, 1.7%, and 7.5%, respectively [10].

The prevalence of UI in this study was lower than in many previous studies, which showed a prevalence of 36.8–48.3% [4, 6, 8, 9]. One reason for this is the variation in the definitions of UI: the current study investigated whether incontinence occurred in the past 4 weeks, whereas many studies utilise a time period of between 1 and 6 months, which may significantly bias the results [4, 6, 8, 9]. A survey conducted in Hebei province, China, showed that the prevalence of UI among women aged 20–70 years was 35.2%, with the 6-month survey duration being an important factor informing the higher prevalence of UI [17].

Severity of UI is a major determinant of QoL and women's willingness to seek medical care [7]. The results of this study suggest that mild, moderate, and severe incontinence accounted for 85.8%, 12.6%, and 1.6%, respectively. According to previous studies, the percentage of severe incontinence fluctuated between 3% and 17% [18]. In terms of the distress caused by UI, women in rural areas appear to be more tolerant as a result of their lower income levels and generally more challenging conditions in which they are accustomed to living. This phenomenon affects the reporting threshold, and appears to account for the lower proportion of severe incontinence in our sample [19, 20].

In common with several previous studies, the most common type of UI was SUI [4, 6,7,8,9,10,11, 19, 20]. However, it was the symptoms of MUI which were more severe and had a greater impact on QoL. A transformation process between subtypes of UI may account for this: a longitudinal study found that although most new UI cases were of the SUI or UUI type, newly diagnosed MUI occurred predominantly in women who had previously reported SUI or UUI [21].

As expected, our study found that in the case of UI, a strong association existed between advanced age, postmenopausal status, and obesity, which has been reported previously [6,7,8, 10, 11]. Obesity leads to a continuous increase in intra-abdominal pressure, which may result in weakness of the pelvic floor muscles and a subsequent elevated risk of UI [22].

In addition, the study revealed that numerous obstetric factors, including multiple vaginal deliveries, large babies, and instrumental vaginal deliveries, were found to significantly increase the probability of UI occurring. During vaginal delivery, the muscles, nerves, and connective tissues of the pelvic floor may suffer varying degrees of damage. Multiparity, macrosomia, and instrumental vaginal deliveries undoubtedly increase this damage and thus further increase the risk of UI [23].

In this study, prior pelvic floor surgery was found to be associated with the occurrence of UI. Because of the large sample size and the nature of the cross-sectional survey, the researchers were unable to refine the details of the specific types of previous pelvic floor surgery amongst participants. The type and severity of de novo UI also require further investigation.

Overall, awareness of UI among rural residents was low, with only 24.7% of respondents reporting that they had heard of UI. Additionally, awareness showed a significant decreasing trend with ageing. A previous study showed that women with UI are prone to self-blame and view UI as a negative consequence of prior childbirth or sexual experiences [24]. In comparison with urban areas, rural populations may lack the necessary knowledge to understand the problem. Furthermore, negative perceptions of UI engender a reluctance to seek medical attention [25]. Our study also shows that almost half of the respondents consider UI to be part of natural ageing; only 17.1% believe that UI can be prevented by taking measures, and some of these women have not sought help due to low expectations of the treatment’s effectiveness. Furthermore, lower education and income levels can further limit the opportunities for medical intervention. In view of China’s ageing population, a rise in the prevalence of UI is to be expected. Strategies for supporting disadvantaged rural female populations in the proper understanding of UI is therefore an urgent issue to be addressed by government, health agencies, and medical staff.

Strengths and limitations

The strength of this study is that it is the largest survey in recent years focusing on the prevalence of female UI in rural China. Furthermore, for the first time, the perception of UI among rural Chinese women was reported, and obtaining accurate data was beneficial for the subsequent pelvic floor health promotion programme. Finally, this study benefited from the familiarity and trusting relationship between the interviewer and the interviewees, as the relationship established by the GPs' usual work with the residents as opposed to a complete stranger facilitated the open expression of privacy-related questions by the participants, resulting in a higher response rate and reliable answers. However, the study also has several limitations, the first being the high proportion of elderly people who refused to participate due to the COVID-19 pandemic. In fact, 188 of the 256 women who declined to participate were older than 55 years, which may have produced a mild degree of bias in the results. Secondly, the use of self-diagnosis, as distinct from urodynamic examination or urine pad test, as the basis of reporting may have produced inaccuracies in the classification and severity of UI.

In conclusion, more than one-fifth of women in rural Fujian suffer from UI, and several factors are thought to be associated with the development of UI. Rural women have a low level of self-awareness of UI, which is worsened by older age and lower levels of education and income, eventually leading to only a small minority seeking medical help. Ways to improve perception of UI in older, low-income and low-education women deserve more attention from government, health agencies, and medical staff.