Abstract
The reported prevalence of urinary incontinence (UI) among women varies widely in different studies due to the use of different definitions, the heterogenicity of different study populations, and population sampling procedures. Population studies from numerous countries have reported that the prevalence of UI ranged from approximately 5% to 70%, with most studies reporting a prevalence of any UI in the range of 25–45%. Prevalence figures increase with increasing age, and in women aged ≥70 years more than 40% of the female population is affected. Prevalence rates are even higher in the elderly-elderly and amongst nursing home patients. There are only a few studies describing progression as well as remission of UI in the general population as well as in selected groups of the population. The mean annual incidence of UI has been reported to range from 1% to 9%, while estimates of remission are more varying, from 4% to 30%. The prevalence of UI is strongly related to the age of the woman and thus, due to the increase in mean life expectancy, the overall prevalence of UI in women is expected to increase in the future.
摘要
由于不同研究中应用的尿失禁（UI）的定义不同、研究人群的异质性以及人群抽样程序的不一, 不同研究中报道的女性UI患病率差异很大。许多国家的人群研究发现, UI的患病率大约在5 ∼ 70%之间, 其中多数研究报道UI的患病率在25%-45%范围内。患病率随着年龄的增长而增加, 在70岁的女性中, 患病率超过40%。在老年人和养老院人群中其患病率更高。仅有少数研究描述了普通人群和特定人群中UI的转归以及缓解情况。据报道, UI的平均年发病率为1 ∼ 9%, 而估计的缓解率差异更大, 范围为4%-30%。UI的患病率与女性的年龄密切相关, 因此, 由于平均预期寿命的增加, 预计女性UI的总体患病率在未来将有所增加。
Introduction
Urinary incontinence (UI) is a highly prevalent condition with a profound influence on well-being and quality of life as well as being of immense economic importance for the health serviceCitation1–4. Millions of women throughout the world are afflictedCitation2,Citation3 and there has been a growing interest in these symptoms as a consequence of the increased awareness of the human and social implications for the individual sufferer. Population-based studies have reported that UI is more common in women than men and that approximately 10% of all adult women suffer from UICitation2,Citation3. Prevalence figures increase with increasing age, and in women aged ≥70 years more than 40% of the female population is affected. Prevalence rates are even higher in the elderly-elderly and amongst nursing home patients.
Inappropriate leakage of urine is perceived by many women but is not always reported to the doctor. However, an increasing awareness of the problem has in recent years attracted more patients to seek advice. In elderly women, UI may lead to possible rejection on the part of a relative and may be an important factor in the decision of whether or not to institutionalize an elderly person. UI not only causes personal suffering for the individual afflicted but is also of considerable economic importance for the health serviceCitation4. The annual cost of UI in Sweden, for example, has been reported to account for approximately 2% of the total health-care budgetCitation1.
Prevalence studies
Prevalence is defined as the probability of experiencing a symptom or having a condition or a disease within a defined population and at a defined time point. The concept is important for establishing the distribution of the condition in the population and for projecting the need for health and medical services. The reported prevalence of UI among women varies widely in different studies due to the use of different definitions, the heterogenicity of different study populations, and population sampling procedures. In addition, different definitions of UI have been applied. Studies of disease frequency should rely on a specific definition of the condition under investigation. The absence of a unifying definition for the condition reviewed is a fundamental problem which has not been resolved.
UI has been defined in the joint report from the International Urogynecological Association/International Continence Society as any involuntary leakage of urineCitation5. However, some authors have chosen to restrict prevalence figures according to the frequency of involuntary urinary leakage – for example, based only on daily, weekly, monthly, or annual urinary leakage. Thus, for the reasons given, it is difficult to compare the results of different population studies. However, when reviewing the literature, there is considerable evidence to support the theory that the prevalence of UI in women increases with age, but there are divergent opinions regarding the pattern of this increaseCitation3.
The prevalence of urinary incontinence
In a reviewCitation3 of population studies from numerous countries, the prevalence of UI ranged from ∼5% to 70%, with most studies reporting a prevalence of any UI in the range of 25–45%. This enormous variation between studies is seen both within and between countries. Few studies report age-standardized rates, which largely precludes a meaningful comparison between countries. If there is a variation in true prevalence rates between countries, it may have been obscured by cultural differences in the perception of UI, a varying willingness to report UI, as well as methodological differences such as the use of different case definitions.
Few studies have used the same survey tools and methods to report the prevalence of female UI in the general population in more than one country (). Three studies have assessed the relative prevalence in western nationsCitation6–8. Across all countries surveyed, all three studies reported stress UI to be the most common subtype, followed by mixed UI and then urge UI. Hunskaar et al.Citation6 surveyed 29,500 women in France, Germany, the UK, and Spain. By demonstration of similar age trends across all countries, they suggested both lower overall prevalence of incontinence in Spain and a relative excess of urge UI in France. The Epidemiology of Incontinence (EPIC)Citation7 and the Epidemiology of Lower Urinary Tract Symptoms (EpiLUTS)Citation8 studies used similar questionnaire items explicitly based on standard definitions. However, there was inconsistency between the studies. The EpiLUTS study found similar prevalence of each UI subtype in the USA, the UK, and Sweden, while the EPIC study reported a more than three-fold variation in prevalence between countries, with Sweden having a prevalence of 29.5% and Italy only 9.3%. The disparity in results could be explained by differences in sampling methods, or different response rates (58%, 33%, and 59%, respectively).
Table 1. Population-based prevalence rates for female urinary incontinence (UI) in studies sampling more than one country.
illustrates the results from two independent studies of UI in women from the same country. In both studies, prevalence was restricted to women who had urinary leakage at least once per week. Although the study performed by Samuelsson et al.Citation9 was undertaken in a rural area and that by Simeonova et al.Citation10 was carried out in an inner city, there are strong similarities between the results of the two studies, with a linear increase in the prevalence of UI which continues over the perimenopausal years.
Figure 1. Comparison of the prevalence of urinary incontinence in two population-based studies of Swedish women. The study by Samuelsson et al.Citation9 was performed in a rural area and the study by Simeonova et al.Citation10 was performed in an inner city.
The prevalence of UI in women has been compared with the prevalence in men of the same age in two large Swedish studiesCitation11,Citation12. As can be seen from the results illustrated in , there is a higher prevalence of UI in women than in men in all of the age groups studied. In general, the prevalence of UI is approximately three times more common in women than in men.
Figure 2. Comparison of the prevalence of urinary incontinence in women and men of the same age resident in the same urban population. Data from two population-based studies which included 7459 womenCitation11 and 7763 menCitation12.
In several studies, attempts have been made to determine the proportion of women suffering from the different types of urinary leakage (i.e. stress UI, urge UI, and mixed UI). In the literatureCitation3, stress urinary leakage tends to dominate among younger women while the numbers of women with urge incontinence and mixed incontinence increase with age.
UI is not static, however, but dynamic and many factors may contribute to the incidence, progression, or remission. There are only a few studies describing progression as well as remission, in the short term, of UI in the general population as well as in selected groups of the population. The mean annual incidence of UI seems to range from 1% to 9%, while estimates of remission are more varying, from 4% to 30%Citation13–15.
Wennberg et al.Citation13 studied the prevalence of UI in the same women (aged ≥20 years) over time in order to assess possible progression or regression. A self-administered postal questionnaire with questions regarding UI, overactive bladder, and other lower urinary tract symptoms was sent to a random sample of the total population of women in 1991. The same women who responded to the questionnaire in 1991 and who were still alive and available in the population register 16 years later were reassessed using a similar self-administered postal questionnaire. The overall prevalence of UI increased from 15% to 28% (p < 0.001) from 1991 to 2007 and the incidence rate of UI was 21%, while the corresponding remission rate was 34%.
Factors influencing the prevalence of urinary incontinence
Risk factors described in the literature are shown in . For the majority of these risk factors, there are at present no controlled trials demonstrating that intervention reduces the incidence, prevalence, or degree of severity of UI.
Table 2. Risk factors for urinary incontinence.
Several studies suggest that the risk of UI ‘runs in the family’Citation3,Citation16–19. Family history studies have found a two-fold to three-fold greater prevalence of stress UI among first-degree relatives of women with stress UI compared to first-degree relatives of continent women. In the Norwegian Nord-Trøndelag health survey (EPINCONT), daughters of mothers with UI had an increased risk of stress UI, mixed UI, and urge UICitation16. In general, the risk was somewhat higher for sisters of a woman with UI than for her daughters.
Studies from the Swedish twin register indicated that heritability contributes to the liability of developing UI. The authors presented evidence that genetic and non-shared environmental factors equally contributed 40% of the variation in liabilityCitation18,Citation19. Although the study methodology and the magnitude of the risk estimates vary, studies on familial transmission of incontinence are in agreementCitation3,Citation16–19: having a first-degree female family member with stress UI increases the risk for an individual becoming afflicted by the same disorder.
The prevalence of UI in nulliparous women of childbearing age has been reported to be 10–15%Citation20–22. Al-Mukhtar Othman et al.Citation23 studied the prevalence of UI in a large cohort of non-pregnant, nulliparous women aged 25–64 years. The overall prevalence of UI was 16.7%. UI increased more than five-fold from 9.7% in the youngest women with a body mass index (BMI) < 25 kg/m2 to 48.4% among the oldest women with a BMI ≥35 kg/m2. The prevalence of bothersome UI almost tripled from 2.8% to 7.9% and the proportion with bothersome UI among incontinent women increased to 32.3% in the age group 55–64 years. Mixed UI increased from 22.9% to 40.9% among the oldest nullipara women (0-para) with incontinence, whereas stress UI alone decreased inversely from 43.6% to 33.0%. In the total cohort, surgical treatment for UI occurred in 3 per 1000 cases.
Many studiesCitation3 have assessed the influence of pregnancy, and in particular vaginal delivery, on the risk of developing UI. UI preceding pregnancy in nulliparous women has been shown to be a strong indicator for increased prevalence of UI 4–12 years postpartumCitation24,Citation25. Pregnancy in itself, independent of labor and delivery practices, seems to be a risk factor for postpartum UICitation26,Citation27, especially if the incontinence started during the first trimesterCitation28. During pregnancy, the prevalence of UI increases with gestational ageCitation29 so that more than half of all women report UI during the third trimesterCitation30–32. Stress UI and mixed UI increased most during pregnancy compared to before pregnancy whereas urge UI did not change during the same periodCitation33. During the first 3 months, the postpartum UI prevalence was 30% and most women had stress UICitation34. In uncomplicated courses of pregnancy and labor, UI usually declines rapidly during the first 3 months following childbirth, indicating that most symptoms are part of a normal pregnancy and deliveryCitation26. Several studies have also demonstrated that postpartum UI is a risk factor for UI after longer (7 months–6 years) terms of follow-upCitation27,Citation35–37.
The first delivery is considered to increase the prevalence of UI the most, and recent studies have demonstrated a further increase for each deliveryCitation11,Citation38–41. Several cross-sectional and several longitudinal studies show a protective effect of Cesarean section for UICitation42–45. BMI is considered to be an established risk factor for UICitation40, whereas the association between UI and age is complicated by confoundersCitation46.
Gyhagen et al.Citation44,Citation45 studied the prevalence of UI 20 years after a single delivery. The risk of developing UI was found to be 71% higher after vaginal delivery than after Cesarean section and the prevalence of UI >10 years almost tripled after vaginal delivery compared to Cesarean section. There was no difference in the prevalence of UI or UI >10 years between women who delivered by acute Cesarean section or elective Cesarean section, indicating that it is during the later stages of delivery, when the fetus passes through the pelvic floor, when the risk of UI increases. Maternal weight was also an important risk factor and, in the multivariate regression analyses, there was an 8% increased risk of UI per BMI unit increase and the rate of UI was apparent for both modes of delivery. Current BMI was the most important BMI determinant for UI and this finding is important, as BMI is modifiable. For women who delivered vaginally, rates of incontinence increased with increasing infant birth weight but this was not observed after Cesarean section. The prevalence of UI increased with maternal age and there was an annual increase in UI prevalence of 3% per year.
Global prevalence
Irwin et al.Citation2 have published data estimating the current and future worldwide prevalence of lower urinary tract symptoms. Age-specific and gender-specific prevalence rates from the EPIC studyCitation7 were applied to the worldwide population over 20 years old (4.2 billion), with males and females stratified into 5-year age groups (20–24 years to 80+ years). Projected population estimates for all worldwide regions were based on the US Census Bureau International Database. Estimates were presented for 2008, 2013, and 2018 and are summarized in and .
Table 3. Estimated number of individuals with urinary incontinence by year and sex.
Table 4. Global estimates of individuals with urinary incontinence grouped by year and region.
Based on the results of the EPIC studyCitation7, the global prevalence of UI was estimated to be 8.7% worldwide. To put this into perspective, with over 421 million people affected, the total prevalence of UI is larger than the total population of the USA (329 million). If UI was a country, it would be the third largest country in the world, surpassed only by India and China.
The global prevalence of urge UI has been assessed in a systematic reviewCitation47. This systematic review identified 54 articles (50 studies); 22 were large-scale, population-based surveys. The prevalence estimates for urge UI ranged from 1.8% to 30.5% in European populations, from 1.7% to 36.4% in US populations, and from 1.5% to 15.2% in Asian populations. Prevalence estimates were highly dependent on age and gender.
Mean life expectancy in the world is increasing, and in some countries 25% of all persons are at present ≥65 years of age. The prevalence of UI is expected to increase in the future and thus there will be a corresponding increase in the number of women requiring treatment for UI. Another important factor to consider, apart from the numerical increase in the number of elderly women, is the fact that many women of today suffer in silence, accepting UI as a normal part of the aging process. Women who are at present 30 and 40 years of age have other demands on their physical condition and will undoubtedly not accept what their older counterparts accepted later in life. Thus, the demands on the health-care services regarding the management of UI are expected to increase in the future, due in part to the aging population.
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