The prevalence and risk factors of different degrees of stress urinary incontinence in Chinese women: A community-based cross-sectional study

Abstract

Aim

To investigate the prevalence of SUI and explore the factors that could influence the severity of SUI in adult females.

Design

A cross-sectional study.

Methods

A total of 1178 subjects were assessed using a risk-factor questionnaires and International Consultation on Incontinence Questionnaire Short Form (ICIQ-SF) and then divided into no SUI group, mild SUI group and moderate-to-severe SUI group according to the ICIQ-SF score. Univariate analysis between adjacent groups and ordered logistic regression models in three groups were then performed to analysis the possible associated factor with the progressive of SUI.

Results

The prevalence of SUI among adult women was 22.2% of them; 16.2% and 6% had mild SUI and moderate-to-severe SUI, respectively. Moreover, logistic analysis revealed that age, BMI, smoking, position preference for urination, urinary tract infections, urinary leaks during pregnancy, gynaecological inflammation and poor sleep quality were independent risk for the severity of SUI.

Conclusion

SUI symptoms were mostly mild among Chinese females, specific risk factors such as unhealthy living habits and urination behaviours increased the risk of SUI and the aggravation of symptoms. Therefore, targeted interventions should be formulated for women to delay disease progression.

INTRODUCTION

According to the International Continence Society, Urinary incontinence (UI) is defined as ‘the complaint of any involuntary loss of urine’, which are divided into three categories: stress urinary incontinence (SUI), urgent urinary incontinence (UUI) and mixed urinary incontinence (MUI). Of these, SUI occurs most common and is the complaint of involuntary leakage of urine due to increased intra-abdominal pressure during coughing, sneezing and laughing (Abrams et al., 2002). Approximately 26% of women in developing countries suffer from urinary incontinence, and the prevalence of stress urinary incontinence (SUI) (12.6%) is far higher than that of mixed urinary incontinence (MUI) (9.1%) and urgent urinary incontinence (UUI) (5.3%; Mostafaei et al., 2020). The largest cross-sectional and population-based epidemiological survey of Chinese females showed that the prevalence of SUI was 18.9% and increased with age to a peak at 50–60 years of age (28.2%) with a gradual decline thereafter (Zhang et al., 2015). SUI can seriously affect a female's quality of life leading to a decrease in work productivity, social isolation, mental disorders, and even increase mortality, which has created statistically significant burden on the healthcare system (Pizzol et al., 2021).

SUI is a dynamic condition in which symptom severity changes over time. Data from longitudinal studies have shown that 12% of women with mild-to-moderate SUI at baseline developed severe SUI and that 38% of women with severe SUI remained in a severe state after 8 years of follow-up. Compared to those with mild UI, women with severe UI were less likely to show an improvement in symptoms (Minassian et al., 2020). To date, only a few studies around the world have supposed that certain lifestyle habits, obstetric or medical factors and even psychosocial factors might also be related to the initiation and progression of SUI, of these, pregnancy and childbirth are known to be important predisposing factors for disease progression. The results of a prospective study showed that the incidence of SUI increased gradually from pre-pregnancy (22.6%) to the pregnancy (37.2%) (Brown et al., 2010). After analysing relationships between chronic conditions and UI, Markland et al found that multiple chronic conditions increased the risk of moderate/severe SUI (Hagan et al., 2018).

Currently, the perspective of studies in China has focused on the overall prevalence and associated factors of SUI. Nevertheless, little is known about how specific modifiable factors influence progressive stages from no SUI to severe SUI in Chinese women. The determination of risk factors in the progression of SUI will benefit the precision prevention and intervention for SUI. In this study, we use cross-sectional data to describe the severity of SUI in adult females living in Chinese communities and identify the potential role of specific factors in different degrees of SUI.

METHODS Participants

This cross-sectional study was conducted in Xuzhou, which is located in the central region of China. A cluster sampling procedure was used to select randomly adult females from six communities. The formula for calculating sample size is ‘N = Z_α/2² * p * (1 − p)/δ²’. Based on the literature (Zhang et al., 2015), the prevalence of SUI among Chinese female is about 18.9%, assuming a 3% error with a 95% confidence level and the non-respondent rata of 20%, the minimum sample size of the final study was determined to be 818.

We included females living in communities, over 18 years of age, who were literate, gave their informed consent willingly to participate. Exclusion criteria:(1) participants who at pregnant or had delivered within the previous 3 months; (2) participants who had experienced urinary obstruction or infection in the previous month; (3) participants who were taking diuretic drugs; (4) perioperative patients with the genitourinary system surgery; (5) participants who suffered from urinary symptoms other than SUI.

Ethics consideration

This study has been approved by the ethics committee of the Xuzhou Medical University and the approval number is XZMU-2020-ZK058. This study was performed according to the ethical principles as stated by the Declaration of Helsinki. Questionnaires (electronic or paper) were distributed on site by the researchers. Firstly, the purpose and methods of the study were explained to each subject in detail, and written informed consent was obtained. The participant was allowed to work through the questionnaires in an independent manner. Anonymity and confidentiality were assured.

Instruments Risk-factor questionnaires

The conceptual framework developed by the Prevention of Lower Urinary Tract Symptoms (PLUS) Consortium highlights the individual and environmental factors that affect bladder health at different stages of a woman's life course (Brady et al., 2018), which was used to design the general information questionnaire in our present study, consisted of three parts: (1) General demographic characteristics (age, BMI, abdominal circumference, marital status, education level, income level, residence, living status); (2) Individual behaviours and occupational factors (smoking, drinking, diet, drinking coffee/tee frequently, frequency of physical activity, duration of daily walking, duration of daily sitting, intensity of work, water-restricted due to work, carrying heavy object, number of toilets at workplace, toileting behaviours). Toileting behaviour was measured using the Chinese Version of Women's Toileting Behaviour Scale (TB-WTBS) (Xiao-juan et al., 2014). This scale has been tested for reliability and validity in female nurses (Cronbach's α 0.80, test–retest reliability coefficient r = 0.93). Confirmatory factor analysis confirmed that the scale had good construct validity, which consists of 17 items assigned to 5 dimensions: preferred place of urination, premature urination, delayed urination, straining to urinate, and preferred position for urination; Each item was rated on a 5-point Likert scale; the higher the score, the more negative the female toileting behaviour. Cronbach's alpha for the whole scale in this study was 0.836. (3) Previous obstetric and medical history factors (number of pregnancies, vaginal deliveries and caesarean sections, urinary leaks during pregnancy, dysmenorrhea, sexual frequency, menstrual status, gynaecological inflammation, family history of UI, number of urinary tract infection, number of chronic diseases, chronic constipation, anxiety, depression, loneliness, sleep quality). Depressive and anxiety symptoms were measured by the Patient Health Questionnaire (PHQ-2) with a specificity of 92% and a sensitivity of 83% (Kroenke et al., 2003) and the generalized anxiety disorder (GAD-2) Questionnaire with a specificity of 83% and a sensitivity of 86% (Kroenke et al., 2007), respectively, which are both associated with good reliability and validity.

Assessment of the severity of SUI

The International Consultation on Incontinence Questionnaire Short Form (ICIQ-UI SF) was developed by International Consultation on Incontinence, we used the validated Chinese version of ICIQ-SF to measure the frequency of UI, the volume of urinary leakage, the impact on daily life and the types of UI in the 4 weeks prior to the study. The test–retest reliability of the scale was 0.72–0.93, and the Cronbach’ α was 0.71–0.96. The whole participants were divided into three groups according to the score provided by the ICIQ (0–21 points). Those answers of ‘none’ to ‘How often have you leaked urine’ and ‘How much do you think you have leaked urine during the last month’, are classified in no SUI group. Women with scores of 1–7 points were classified in mild SUI group; Moderate SUI (8–14 points) or severe UI (15–21 points) were combined into a single ‘moderate-to-severe’ category of SUI due to the small number of cases experiencing severe SUI.

Statistical analysis

All statistical analysis was carried out by SPSS software (version 25.0). the Chi-squared test was used to analyse differences in categorical variables. Partitioning of the Chi-squared method was used for pairwise comparisons on the basis of statistical significance, and significance was determined by calculation (α' = α/($\frac{k\left(k-1\right)}{2}$+1) = 0.0125, k represents the number of groups). Differences between continues variables were evaluated by one-way analysis of variance (ANOVA) and Kruskal–Wallis test followed by Dunn's multiple comparison. The multivariable ordinal logistic regression analysis based on a significance level of 0.05 was also applied to identify independent risk factors for the severity of SUI.

RESULTS General characteristics of the survey subjects

A total of 1178 women who met the study eligibility (Figure 1), with a mean age of 44.09 ± 17.21 years and a mean BMI of 23.12 ± 3.25 kg/m². Analyses showed that 70.9% were married and 53.0% had received college or undergraduate degree. In total, 262 women (22.2%) had SUI, 191 (72.9%) had mild SUI (mean age: 53.46 ± 15.37 years) and 71 (27.1%) had moderate-to-severe SUI (mean age: 49.23 ± 13.97 years). The distribution of SUI severity across different age groups is shown in Figure 2.

FIGURE 1. Flow diagram of subjects inclusion in this study.

FIGURE 2. Severity of SUI according to age-group distribution.

Univariate analysis of factors associated with different severities of SUI Socio-demographic characteristics

Analysis showed that the age, BMI and abdominal circumference of females with mild SUI were significantly higher than in the no SUI group (all p < 0.001). We also identified other statistically significant differences between the two groups: marital status, educational level and monthly income (all p < 0.0125). BMI was significantly lower in females with moderate-to-severe SUI than in those with mild SUI (p = 0.001; Table 1).

TABLE 1 Comparisons of socio-demographic characteristics between subjects with different severities of SUI.

Continuous variables mean ± SD	No SUI (n = 916)	Mild SUI (n = 191)	Moderate-to-severe SUI (n = 71)	p-value
Age (years)b	41.73 ± 17.06	53.46 ± 15.37**	49.23 ± 13.97	<0.001
BMI (kg/m2)b	22.77 ± 3.19	24.67 ± 3.43**	23.40 ± 2.47##	<0.001
Categorical variables n (%)
Abdominal circumferencea		**		<0.001
<80	5129 (5.9)	66 (34.6)	29 (40.8)
≥80	404 (44.1)	125 (65.4)	42 (59.2)
Marital Statusa		**		<0.001
Unmarried	251 (27.4)	5 (2.6)	3 (4.2)
Married	602 (65.7)	172 (90.1)	61 (85.9)
Widowed/Divorced	63 (6.9)	14 (7.3)	7 (9.9)
Education levela		**		<0.001
Junior school and below	224 (24.5)	93 (48.7)	29 (40.8)
High and technical school	112 (12.2)	33 (17.3)	17 (23.9)
Undergraduate degree	537 (58.6)	62 (32.5)	25 (35.2)
Master degree and above	43 (4.7)	3 (1.6)	0 (0.0)
Income levela		**		0.005
<1000	80 (8.7)	28 (14.7)	8 (11.3)
1000–5000	421 (46.0)	101 (52.9)	28 (39.4)
>5000	415 (45.3)	62 (32.5)	35 (49.3)

Abbreviations: BMI, body mass index; SD, standard deviation.

^aChi-squared test.

^bOne-way analysis of variance.

^**Statistically different at p < 0.0125, No SUI group versus Mild SUI group.

^##Statistically different at p < 0.0125, Mild SUI group versus Moderate-to-severe SUI group.

Individual behaviour and occupational factors

Analysis identified a statistically significant differences between the no SUI group and the mild SUI group with regards to smoking, diet, intensity of work and the number of toilets at workplace(all p < 0.0125). There were also statistical differences between the mild and moderate-to-severe SUI groups in terms of drinking coffee/tea frequently, the number of toilets at workplace and the preferred position for urination (all p < 0.0125; Table 2).

TABLE 2 Comparisons of individual behaviour and occupational factors between subjects with different severities of SUI.

Categorical variables	No SUI (n = 916)	Mild SUI (n = 191)	Moderate-to-severe SUI (n = 71)	p-value
Smokinga		**		<0.001
No	894 (97.6)	177 (92.7)	62 (87.3)
Yes	22 (2.4)	14 (7.3)	9 (12.7)
Dieta		**		0.001
Mainly vegetables	212 (23.1)	68 (35.6)	19 (26.8)
Mainly meat protein	84 (9.2)	6 (3.1)	7 (9.9)
Balanced diet	620 (67.7)	117 (61.3)	45 (63.4)
Drinking coffee/tee frequentlya			##	0.016
No	765 (83.5)	170 (89.0)	53 (74.6)
Yes	151 (16.5)	21 (11.0)	18 (25.4)
Duration of daily walkingb		*		0.024
<30 min	244 (26.6)	34 (17.8)	14 (19.7)
30 min-1 h	338 (36.9)	73 (38.2)	29 (40.8)
1 h	334 (36.6)	84 (44.0)	28 (39.4)
Duration of daily sittinga				0.007
<1 h	98 (10.7)	16 (8.4)	2 (2.8)
1–3 h	310 (33.8)	76 (39.8)	37 (52.1)
3–5 h	254 (27.7)	61 (31.9)	17 (23.9)
>5 h	254 (27.7)	38 (19.9)	15 (21.1)
Intensity of worka		**		0.012
Light	404 (44.1)	63 (33.0)	22 (31.0)
Moderate	439 (47.9)	114 (59.7)	41 (57.7)
Hard	73 (8.0)	14 (7.3)	8 (11.3)
Carrying heavy objectsa				0.009
Never	195 (21.3)	43 (22.5)	15 (21.1)
Occasionally	630 (68.8)	120 (62.8)	40 (56.3)
Often/always	91 (9.9)	28 (14.7)	16 (22.5)
Number of toilets at workplacea		**	##	0.004
None/less	268 (29.3)	36 (18.8)	26 (36.6)
Sufficient	648 (70.7)	155 (81.2)	45 (63.4)
Toileting behaviour
M (P25, P75)
Preferred place for urinationc	13 (10, 15)	13 (10, 16)	15 (12.5, 16)	0.004
Premature urinationc	9 (6, 12)	10 (8, 13)*	12 (6.5, 16)	<0.001
Delayed urinationc	8 (7, 10)	8 (7, 10)	9 (7, 11)#	0.027
Straining to urinatec	7 (4, 11)	7 (4, 9)	8 (5, 12)#	0.035
Preferred position for urinationc	4 (2, 5)	3 (2, 5)	6 (3, 6)##	<0.001

^aChi-squared test.

^bChi-squared test (for linear-trend).

^cKruskal–Wallis H test for toileting behaviours.

^*Statistically different at p < 0.05.

^**Statistically different at p < 0.0125, No SUI group versus Mild SUI group.

^#Statistically different at p < 0.05.

^##Statistically different at p < 0.0125, Mild SUI group versus Moderate-to-severe SUI group.

Previous obstetric and medical history factors

The mean number of pregnancies (2.19 ± 1.29) and vaginal deliveries in the mild SUI group (1.51 ± 1.05) were higher than that in the no SUI group (1.55 ± 1.48) and (0.86 ± 1.04; all p < 0.001). The number of caesarean sections in the moderate-to-severe.

SUI group (0.24 ± 0.52) was higher than that in the mild SUI group (0.11 ± 0.38) (p = 0.012). Urinary tract infections and chronic diseases in the mild SUI group was higher than that in the no SUI group, and mild SUI group were more likely to report loneliness and poor sleep quality (all p < 0.0125). We also identified a statistically significant differences between the mild SUI group and the moderate-to-severe SUI group with regards to chronic constipation and sleep quality(all p < 0.0125; Table 3).

TABLE 3 Comparisons of previous obstetric and medical history between subjects with different severities of SUI.

Continuous variables	No SUI (n = 916)	Mild SUI (n = 191)	Moderate-to-severe SUI (n = 71)	p-value
Number of pregnanciesc	1.55 ± 1.48	2.19 ± 1.29**	2.36 ± 1.50	<0.001
umber of vaginal deliveriesc	0.86 ± 1.04	1.51 ± 1.05**	1.56 ± 1.31	<0.001
Number of caesarean sectionsc	0.21 ± 0.54	0.11 ± 0.38*	0.24 ± 0.52##	<0.001
Categorical variables
Urinary leaks during pregnancya		**		<0.001
Yes	48 (5.2)	35 (18.3)	50 (70.4)
No	868 (94.8)	156 (81.7)	21 (29.6)
Sexual frequency (times/week)a			##	0.002
0	467 (51.0)	98 (51.3)	23 (32.4)
1–5	350 (38.2)	77 (40.3)	44 (62.0)
6–10	80 (8.7)	16 (8.4)	2 (2.8)
>10	19 (2.1)	0 (0.0)	2 (2.8)
Menstrual statusa		**		<0.001
Regular	529 (57.8)	68 (35.6)	26 (36.6)
Irregular	123 (13.4)	19 (9.9)	13 (18.3)
Perimenopausal	45 (4.9)	11 (5.8)	8 (11.3)
Menopausal	219 (23.9)	93 (48.7)	24 (33.8)
Gynaecological inflammationa		**		<0.001
Yes	160 (17.5)	61 (31.9)	39 (54.9)
No	756 (82.5)	130 (68.1)	32 (45.1)
Family history of UIa				<0.001
Yes	69 (7.5)	20 (10.5)	15 (21.1)
No	847 (92.5)	171 (89.5)	56 (78.9)
Number of urinary tract infectionsb		**		<0.001
0	702 (76.6)	113 (59.2)	38 (53.5)
1	151 (16.5)	45 (23.6)	12 (16.9)
2	36 (3.9)	16 (8.4)	9 (12.7)
>2	27 (2.9)	17 (8.9)	12 (16.9)
Number of chronic diseasesb		**		<0.001
0	678 (74.0)	95 (49.7)	38 (53.5)
1	163 (17.8)	49 (25.7)	22 (31.0)
2	50 (5.5)	23 (12.0)	5 (7.0)
>2	25 (2.7)	24 (12.6)	6 (8.5)
Chronic constipationa			##	<0.001
Yes	167 (18.2)	29 (15.2)	28 (39.4)
No	749 (81.8)	162 (84.8)	43 (60.6)
Lonelinessa		**		0.013
Never/rarely	625 (68.2)	105 (55.0)	45 (63.4)
Sometimes	247 (27.0)	74 (38.7)	22 (31.0)
Often/always	44 (4.8)	12 (6.3)	4 (5.6)
Sleep qualitya		**	##	<0.001
Very good	192 (21.0)	21 (11.0)	4 (5.6)
Moderate	565 (61.7)	112 (58.6)	20 (28.2)
Poor	159 (17.4)	58 (30.4)	47 (66.2)

^aChi-squared test.

^bChi-squared test (for linear-trend).

^cOne-way analysis of variance.

^*Statistically different at p < 0.05.

^**Statistically different at p < 0.0125, No SUI group versus Mild SUI group.

^#Statistically different at p < 0.05.

^##Statistically different at p < 0.0125, Mild SUI group versus Moderate-to-severe SUI group.

Multivariate logistic analysis of factors associated with different severities of UI

We performed regression analysis with the variables, which show a statistically significant difference among the three groups to determine the risk factors for the severity of SUI, and result are displayed that age, BMI, smoking, position preference for urination, urinary tract infections, urinary leaks during pregnancy, gynaecological inflammation, and poor sleep quality were identified as independent risk factors associated with the progression of SUI. Among them, smoking (OR = 3.581, 95% CI = 1.820–7.045) and urinary leaks during pregnancy (OR = 3.520, 95% CI = 2.167–5.717) were of the most important factor (Table 4).

TABLE 4 Ordinal logistic regression models for the three severity categories of SUI group.

Variable	β	SE	Waldχ2	OR	95% CI	p
Age	0.025	0.0125	3.977	1.025	1.000–1.050	0.046
BMI	0.071	0.033	4.533	1.073	1.006–1.145	0.033
Smoking	1.276	0.345	13.645	3.581	1.820–7.045	<0.001
Position preference for urination	0.097	0.470	4.259	1.102	1.005–1.208	0.039
Number of urinary tract infections
>1				1.000
1	−0.762	0.273	7.795	0.467	0.273–0.797	0.005
0	−0.969	0.234	17.139	0.379	0.240–0.600	<0.001
Urinary leaks during pregnancy	1.258	0.247	25.864	3.520	2.167–5.717	<0.001
Gynaecological Inflammation	0.709	0.194	13.345	1.591	1.389–2.972	<0.001
Sleep quality
Poor				1.000
Moderate	−0.803	0.191	17.590	0.448	0.308–0.652	<0.001
Very good	−1.085	0.295	13.537	0.338	0.190–0.602	<0.001

Abbreviations: 95% CI, 95% confidence interval; OR, odds ratio.

DISCUSSION

Several longitudinal studies previously have preliminarily explored the natural course of urinary incontinence and confirmed dynamic and progressive of the disease. However, there is no uniform conclusion regarding factors that influence SUI occurrence and progression, especially in Chinese women. This is, to our knowledge, the first study to comprehensively examine related risk factors for different degrees of SUI in Chinese women, which incorporated a large number of factors based on potential risk factors proposed by the conceptual framework of the Prevention of Lower Urinary Tract Symptoms (PLUS). In addition, the strength of this study is that it was a large sample survey, and adopted a cross-sectional study design to reflex the progression of SUI, thus providing statistically significant insight into the factors that affect the dynamic progression of this disease. Here, we focused on analysing the role of the modifiable factors such as occupational and behavioural factors at different stages of SUI progression.

The prevalence of SUI

The prevalence of female SUI in different regions of China is known to differ significantly due to geographical and lifestyle factors. Our results indicate that the prevalence of SUI in adult females was 22.2%, mild SUI was dominant (72.9%) and the prevalence of SUI increased with age. These findings were consistent with those reported previously by Tao et al (Li et al., 2019). In addition, the mean age of females with mild symptoms was higher than that of women with moderate-to-severe SUI, thus highlighting the fact that age is not the main factor responsible for the exacerbation of symptoms. Similarly, a previous survey in Taiyuan also reported the lack of an association between age and SUI (Zhang et al., 2021). It is possible that young women may have experienced childbirth and heavy labour more recently, thus increasing the risk of severe SUI. Furthermore, older females could have adapted to this status with a longer duration of SUI, thereby underestimating the severity. In our study, women with moderate-to-severe symptoms were mostly 40 to 50 years of age, this is a stage where many women start experiencing menopause and a decline in oestrogen levels, thus leading to atrophy of the genitourinary system and the aggravation of UI (Calleja-Agius & Brincat, 2015).

Risk factors for the severity of SUI

Understanding the causes underlying the transition from a normal state to UI and the severity of SUI worsened is essential if we are to develop interventions to reduce the incidence of urinary incontinence. In our study, the variables with statistical difference between no UI group and mild UI group are different from those between mild and moderate severe groups. According to our final ordinal logistic regression models, 7 factors increased the odds of the severity of SUI and thus those factors that are modifiable.

Age and body mass index (BMI) are recognized as the main risk factors of urinary incontinence. Obtained result from this study indicated there was an increased risk of aggravated symptoms with increasing age and BMI. BMI is a modifiable factor compared with age. According to the latest detailed survey on obesity in China released by the Chinese Center for Disease Control and Prevention, the total number of obese women in China has increased from 16 million in 2004 to 37 million in 2018 (Wang et al., 2021). Evidence shows that the incidence of urinary incontinence can be improved by 12%–17% within 1–2.9 years by weight loss intervention (Yazdany et al., 2020). Therefore, healthcare providers should strengthen the nutrition and exercise guidance for women and control their weight to prevent the occurrence of SUI, thus, generate higher quality of life of women in the middle and late life.

Previous studies have reported the impacts of some female behaviours and habits on the progression of urinary incontinence (Chu et al., 2019). For example, the relationship between smoking and UI has been investigated many times, However, the conclusions remain contradictory (Kawahara et al., 2020; Madhu et al., 2015). In our study, we found that smoking increased the risk of the severity of SUI. Smoking is more likely to cause respiratory diseases and chronic cough, these factors can both induce SUI. In addition, smoking-induced atherosclerosis is known to play a role in pelvic blood flow disorders that can ultimately lead to chronic ischemic bladder dysfunction (Andersson et al., 2014). Due to the small number of smokers in the present study, the effect of smoking on SUI may have been overestimated.

Recently, the relationship between toileting behaviour and urinary incontinence has been gradually observed. Many women used hovering or couching positions in order to avoid contacting with the toilet bowl when using the public toilets. These postures would make the pelvic floor muscles continuously tense during urination, thus resulting in an increase in the post-void residual urine volume (Moore et al., 1991). A previous study found that sitting on the toilet completely and leaning forward can increase abdominal pressure and relax the pelvic floor muscles, thus emptying the bladder more effectively (Rane & Iyer, 2014). Therefore, it is very important for community nurses to understand the toileting behaviour of women and provide health education with regards to bladder emptying.

Notably, we identified urine leakage during pregnancy was the strongest predictor of the severity of SUI in the present study, this was consistent with findings of a previous meta-analysis (Wang et al., 2020). The reason of urine leakage during pregnancy is unclear at this time and may be related to the physiological changes during pregnancy result in weakening of pelvic floor muscle strength, or the increase of hormone secretion, the defect of pelvic floor collagen tissue and the changes of related neurons during pregnancy. Therefore, this suggests that obstetricians and midwives should considered women who leak urine during pregnancy as high-risk population for postpartum urinary incontinence during postpartum follow-up. Parturients should be informed about alarm symptoms and encouraged to seek an immediate consultation with their physician.

This study found that urinary tract infection and gynaecological inflammation can also aggravate the symptoms of SUI. Inflammation affects the synthesis and metabolism of connective tissue, damages pelvic floor ligament and promotes the occurrence and development of urinary incontinence, which is consistent with other research conclusions (Jiang et al., 2016). Patients with urinary infections often have frequent urination, urgency and poor urination symptoms, which may induce women to alter toilet behaviour, such as straining abdominal muscles and pelvic floor muscles to empty bladder fast or frequent holding urine, consequently leading to SUI. This suggests that healthcare staff should understand the current status of perineum hygiene among community women in time, focus on women's coping strategies when early symptoms of urinary system appear and formulate targeted intervention measures.

We observed a strong association between poor sleep quality and more severe SUI symptoms, this finding was consistent with a previous study (Ge et al., 2017). From another perspective, SUI is also an important factor that can lead to sleep disorders (Nazaripanah et al., 2018), psychological distress such as anxiety and depression, frequent nocturia, and damp clothes and an unpleasant smell of urine; all of these factors can reduce sleep quality. The cause-effect relationship between UI and sleep disorders cannot be proven conclusively by our current data due to the cross-sectional nature of this study. A longitudinal study is now needed to identify how the symptoms of SUI may affect sleep and vice versa.

This study also has limitations that need to be considered. First, the occurrence and severity of urinary incontinence are reported entirely on the basis of self-reporting. Consequently, our data may have been affected by recall bias and the concealment of information. Because of the relative exacerbation or remission of SUI, it is possible that patients in remission may have been misjudged and classified into the no SUI group during cross-sectional investigation. Second, all participants were from the same city; this may have resulted in population selection bias. Consequently, our findings should be interpreted with caution. What's more, it could not establish a causal relationship due to the cross-sectional study design, and further longitudinal studies are required to verify our findings.

In conclusion, we demonstrated that SUI symptoms were mostly mild in severity among Chinese females, and age, BMI, smoking position preference for urination, urinary tract infections, urinary leaks during pregnancy, gynaecological inflammation, poor sleep quality affected the more severe state of SUI. More reliable research methods and large epidemiological surveys are now needed to clarify the natural course of SUI and the causal relationship with specific factors. Screening for urinary system symptoms of female is recommended, the high-risk groups and incontinent individuals should be targeted for more frequent health education on the topic of UI.

ACKNOWLEDGEMENTS

The authors thank all the subjects for their participation and community staffs for their assistance.

ETHICS STATEMENT

This study was approved by the ethics committee of the Xuzhou Medical University with registration number XZMU-2020-ZK058.

FUNDING INFORMATION

The study was supported by the Chinese Postdoctoral Science Foundation (Grant no. 2018T110553). The funding source had no role in the design, practice or analysis of this study.

CONFLICT OF INTEREST STATEMENT

All authors declare that they have no competing interests.