Volume 197, Issue 2 , Pages 167.e1-167.e5, August 2007
Incidence and remission of urinary incontinence in middle-aged women
Article Outline
Objective
The objective of the study was to describe changes in urinary incontinence in middle-aged women.
Study Design
A prospective analysis of 64,650 women aged 36-55 years in the Nurses’ Health Study II. Participants reported urine leaking in 2001 and 2003. Two-year incidence and remission proportions were estimated.
Results
The 2-year incidence of incontinence was 13.7%. Incidence generally increased through age 50 years and then declined slightly in older women. Among women with incident incontinence at least weekly, the incidence of stress incontinence increased through age 50 years (2-year incidence 1.7%), and the incidence of urge incontinence was stable across age groups (2-year incidence 0.4%). Also, a minority (38%) mentioned leaking to their physician. Complete remission of symptoms occurred in 13.9% of women with incontinence at baseline.
Conclusion
We found that incontinence occurs frequently in middle-aged women. Yet few women mentioned incontinence to their physicians; thus, it may be important to initiate conversations about urinary symptoms even among younger patients.
Key words: epidemiology, incidence, urinary incontinence
Urinary incontinence is a dynamic condition with a multitude of factors contributing to its development, progression, and recession.1 Nonetheless, epidemiologic studies have focused primarily on estimating the prevalence of urinary incontinence in women at a single point in time and devoted less attention to characterizing its development and natural history.2 Among the few studies that have examined the incidence of urinary incontinence, limited sample sizes have prevented precise estimation of incidence proportions by incontinence severity or type. Furthermore, very little is known regarding changes in incontinence severity over time, including remission or improvement of symptoms. In particular, data on incontinence incidence in middle-aged women are rarely reported, although incontinence can be associated with important social as well as medical issues.3, 4 Detailed documentation of the magnitude of incontinence in this age group could be critical information helping physicians decide whether to routinely initiate discussion of urinary symptoms with their younger patients.
Therefore, we described urinary incontinence incidence, including by incontinence type, and changes in incontinence severity over 2 years in a large, prospective cohort of women aged 36-55 years enrolled in the Nurses’ Health Study (NHS) II.
Materials and Methods
Study population
The NHS II cohort was established in 1989 when 116,671 female nurses aged 25-42 years in 14 states completed a mailed questionnaire about their medical history, lifestyle, and health behaviors. Questionnaires are sent to participants every 2 years and follow-up rates of the cohort have remained approximately 95% through 2001. To maintain high follow-up, 5 mailing cycles of the questionnaire are conducted; for later cycles, only an abbreviated version of the questionnaire is sent. Information on urinary incontinence was requested on the long versions of the 2001 and 2003 questionnaires. In 2003 we also mailed a supplementary questionnaire to incident cases with at least weekly incontinence to gather more detailed information about urinary incontinence symptoms.
In 2001, 115,713 participants were still alive and were sent a questionnaire. Of these, 85,994 completed the long version of the questionnaire in 2001, and 70,712 women also returned the long version in 2003. We further excluded those with missing data on incontinence at baseline or follow-up (n = 349), and women whose continence status at baseline was unclear (ie, those who reported leaking less than once per month of quantities at least enough to wet the underwear [n = 5713]). Thus, 64,650 women were considered in analyses. Compared with women not included in analyses, these women were highly similar in key risk factors for incontinence, including mean age, body mass index, parity, cigarette smoking status, and menopausal status; thus, it seems unlikely that there would be any meaningful bias in our population for analysis.
The study was approved by the Institutional Review Board of Brigham and Women’s Hospital.
Urinary incontinence incidence
The 2001 and 2003 NHS II questionnaires included 2 questions about leaking urine. First, participants were asked, “During the last 12 months, how often have you leaked or lost control of your urine?”; response categories were never, less than once per month, once per month, 2-3 times per month, about once per week, and almost every day. Women who reported leaking urine were then asked, “When you lose your urine, how much usually leaks?” Response categories were a few drops, enough to wet your underwear, enough to wet your outer clothing, and enough to wet the floor.
A reliability study5 conducted in a similar group of nurses demonstrated high reproducibility of self-reported frequency and quantity of leaking urine, with 90% responding similarly to the item regarding frequency and 98% responding similarly to the item regarding quantity of leaking, on 2 questionnaires several months apart.
For analyses of incident incontinence, participants who reported never leaking or leaking a few drops less than once per month in 2001 were considered at risk of developing incident incontinence (n = 33,952). Among these women, incident incontinence was categorized as incident occasional urine loss, defined as leaking 1 to 3 times per month in 2003; or incident frequent urine loss, defined as leaking at least once per week in 2003. In addition, to define cases of severe leaking, we used the validated Sandvik Severity Index,6 which considers severe leaking as frequent urine loss of at least enough to wet the underwear.
Urinary incontinence type
For reasons of efficiency (ie, the large number of incident cases) and accuracy (ie, we believed that identification of symptoms would be easier for women with more frequent leaking), we mailed a supplementary questionnaire to a subset of incident cases of frequent leaking in 2003 (n = 1224; response rate 79%). Important incontinence risk factors, including mean age and parity, were similar in incident cases of frequent leaking who did complete the supplementary questionnaire and those who did not.
Questions about specific urinary symptoms used in a previous epidemiologic study7 were used to assess incontinence type. Participants were asked about the primary circumstances surrounding urine loss: the presence of urge incontinence symptoms, including urine loss that occurred when a toilet was not accessible or with a sudden feeling of bladder fullness, or stress incontinence symptoms, including urine loss caused by coughing or sneezing, lifting things, laughing, or brisk walking or exercise. When women reported equal predominance of urge and stress symptoms, incontinence type was classified as mixed; otherwise, incontinence type classifications were determined by the women’s characterizations of their dominant symptoms.
Urinary incontinence remission and improvement
In analyses of incontinence remission and improvement, we included women reporting at least monthly incontinence in 2001 (n = 30,698). Complete remission was then defined as a report of no leaking in 2003. In addition, incontinence improvement was defined as either complete remission or a decrease in leaking frequency from 2001 to 2003.
Data Analysis
Two-year incidence proportions were calculated by dividing the number of cases by the total number of women at risk in 2001. Proportions were calculated separately for each case definition based on frequency of symptoms, severity of symptoms, and incontinence type. Incident cases of frequent incontinence who did not complete the supplementary questionnaire were excluded from the calculations (ie, from both the numerator and denominator) of incontinence type. Analyses of incontinence remission and improvement were conducted similarly to those above. Specific comparisons of groups (eg, age 51-55 vs age 46-50 years) were conducted using the 2-sample test for binomial proportions.
Results
Overall, there were 64,650 women included in these analyses, among whom 33,952 were at risk for developing incident incontinence in 2001. Among all women, the mean age was 46.4 years (Table 1). The prevalence of overweight and obesity (body mass index 25 kg/m2 or greater) was 50.3%, and 79.0% were parous. Among continent women in 2001, the mean age was 46.0 years, 42.8% were overweight or obese, and 76.4% were parous (Table 1).
TABLE 1. Characteristics of Nurses’ Health Study II participants in 2001
| Characteristic | Study population (n = 64,650)⁎ | At risk for incident UI (n = 33,952)⁎ | ||
|---|---|---|---|---|
| n | % | n | % | |
| Age (y) | ||||
 36-40 | 8555 | 13.2 | 5034 | 14.8 |
| 41-45 | 18,832 | 29.1 | 10,387 | 30.6 |
| 46-50 | 22,490 | 34.8 | 11,413 | 33.6 |
| 51-55 | 14,773 | 22.9 | 7118 | 21.0 |
| Body mass index (kg/m2) | ||||
| Less than 22 | 14,718 | 22.8 | 9417 | 27.7 |
| 22-24 | 16,920 | 26.2 | 9730 | 28.7 |
| 25-29 | 17,295 | 26.8 | 8697 | 25.6 |
| 30 or greater | 15,226 | 23.6 | 5823 | 17.2 |
| Missing | 491 | 0.8 | 285 | 0.8 |
| Parity | ||||
| None | 11,826 | 18.3 | 7083 | 20.9 |
| 1 birth | 8555 | 13.2 | 4458 | 13.1 |
| 2 births | 25,140 | 38.9 | 12,637 | 37.2 |
| 3 or more births | 17,350 | 26.8 | 8840 | 26.0 |
| Missing | 1779 | 2.8 | 934 | 2.8 |
| Type 2 diabetes mellitus | 1821 | 2.8 | 735 | 2.2 |
⁎Study population includes women with leaking frequency information in 2001 and 2003; at-risk population includes the subset of the study population with no leaking or leaking a few drops less than once per month in 2001. |
Urinary incontinence incidence
The overall 2-year incidence of urinary incontinence was 13.7%, which corresponds to an average incidence of 6.9% per year (Table 2). Incidence generally increased across ages 36 through 50 years; however, after age 50 years (ie, 51-55 years), there was a small decline. This decline was significant for severe incontinence (P = .01 comparing the 2 oldest age groups).
TABLE 2. Two-year incidence of urinary incontinence by severity of incontinence
| Age (y) | N | Any Incontinence⁎ | Occasional Incontinence⁎ | Frequent Incontinence⁎ | Severe Incontinence⁎ | ||||
|---|---|---|---|---|---|---|---|---|---|
| Subjects | % | Subjects | % | Subjects | % | Subjects | % | ||
| 36-40 | 5034 | 593 | 11.8 | 473 | 9.4 | 120 | 2.4 | 42 | 0.8 |
| 41-45 | 10,387 | 1374 | 13.2 | 1006 | 9.7 | 368 | 3.5 | 127 | 1.2 |
| 46-50 | 11,413 | 1681 | 14.7 | 1207 | 10.6 | 474 | 4.2 | 177 | 1.6 |
| 51-55 | 7118 | 1020 | 14.3 | 738 | 10.4 | 282 | 4.0 | 78 | 1.1 |
| Total | 33,952 | 4668 | 13.7 | 3424 | 10.1 | 1244 | 3.7 | 424 | 1.2 |
⁎Any incontinence is defined as leaking at least once per month; occasional incontinence is defined as leaking 1-3 times per month; frequent incontinence is defined as leaking at least once per week; severe incontinence is defined as frequent leaking of quantities at least enough to wet the underwear. |
We classified urinary incontinence by type among women with incident frequent incontinence during the follow-up period (Table 3). Similar to the overall pattern, the incidence of stress incontinence increased with age (from 1.2% to 1.9% across age 36-50 years). However, the incidence of urge incontinence was lower and nearly identical across age categories. Slightly more women reported incident mixed incontinence, compared with urge incontinence, and the incidence increased steadily with increasing age.
TABLE 3. Two-year incidence of frequent⁎ urinary incontinence by incontinence type†
| Age (y) | n | Stress | Urge | Mixed | |||
|---|---|---|---|---|---|---|---|
| Subjects | % | Subjects | % | Subjects | % | ||
| 36-40 | 5012 | 58 | 1.2 | 22 | 0.4 | 17 | 0.3 |
| 41-45 | 10,307 | 189 | 1.8 | 38 | 0.4 | 58 | 0.6 |
| 46-50 | 11,301 | 219 | 1.9 | 58 | 0.5 | 79 | 0.7 |
| 51-55 | 7056 | 123 | 1.7 | 30 | 0.4 | 62 | 0.9 |
| Total | 33,676 | 589 | 1.7 | 148 | 0.4 | 216 | 0.6 |
⁎Defined as leaking at least once per week. |
†Cases of incident frequent incontinence with missing data on incontinence type symptoms are excluded from these calculations. |
Interestingly, among the incident cases with frequent incontinence, we found only 38% reported mentioning their symptoms to a physician. Moreover, just 13% reported receiving treatment for their incontinence.
Urinary incontinence remission and improvement
We also examined changes in incontinence frequency among women with incontinence at baseline (Table 4). Change patterns were similar in women older than age 45 years and in younger women; therefore, we collapsed the data into 10-year age categories. Overall, 13.9% of women who reported leaking at least once per month at the beginning of follow-up reported no leaking 2 years later. Furthermore, complete incontinence remission was more common in the younger women. For example, among women who reported incontinence in 2001, 17.1% of women aged 36-45 years reported no leaking in 2003, compared with 11.9% of women aged 46-55 years (P < .001). Remission was more common in women with frequent than with occasional incontinence; 18.3% of women with frequent incontinence in 2001 reported incontinence remission, compared with only 7.4% of women with occasional incontinence in 2001.
TABLE 4. Changes in urinary incontinence between 2001 and 2003 among women with prevalent urinary incontinence at baseline
| 2001 | 2003 (n [%]) | ||||
|---|---|---|---|---|---|
| None | Less than 1/month | 1-3/month | 1 or more/wk | Total | |
| Age 36-45 y | |||||
| 1-3/month | 398(8.0) | 1267(25.5) | 2070(41.7) | 1229(24.8) | 4964(100.0) |
| 1 or more/wk | 1648(23.5) | 843(12.0) | 1225(17.5) | 3286(46.9) | 7002(100.0) |
| Age 46-55 y | |||||
| 1-3/month | 513(6.9) | 1877(25.3) | 3061(41.3) | 1964(26.5) | 7415(100.0) |
| 1 or more/wk | 1710(15.1) | 1154(10.2) | 2090(18.5) | 6363(56.2) | 11,317(100.0) |
When we examined general improvement of incontinence from 2001 to 2003 (Table 4), we considered both complete remission as well as any decrease in the frequency of leaking. Among women who initially had 1-3 incontinence episodes per month, improvement was reported by 32.8%. This percentage was similar in women across age groups. Among women who reported incontinence at least once per week at baseline, symptoms were more likely to decrease in younger women, compared with older women: 53.1% of women aged 36-45 years improved, compared with 43.8% of women aged 46-55 years (P < .001). Although part of these improvements may be due to treatment, we did not collect information on treatment for incontinence among women with incontinence at baseline. However, as mentioned earlier, among women with incident incontinence, few reported any medical treatment. Finally, 59% of the prevalent incontinence cases in 2001 reported a similar or increased frequency of leaking episodes over 2 years.
Recent pregnancies and childbirths may have influenced the observed incidence and remission proportions, particularly among the younger women in our study population. However, only a small proportion of the women in the study population (3%) reported a pregnancy within the last 2 years, and estimates excluding these women were quite similar to those reported earlier.
Comment
Overall, in this prospective study, 13.7% of women aged 36-55 years who reported no leaking or minimal leaking developed at least monthly incontinence over the next 2 years, corresponding to an average incidence of 6.9% per year. In general, the incidence tended to increase with age through age 50 years; however, the incidence stabilized or declined at age 51-55 years. Among incontinent women at baseline, 13.9% reported complete remission of their symptoms at the end of follow-up, although the majority of incontinent women at baseline reported a similar or greater frequency of leaking episodes 2 years later.
Few data exist on urinary incontinence incidence in women under age 60 years and, in particular, women under age 40 years; thus, our data provide important information regarding the high magnitude of incontinence in younger age groups. The limited previous studies have generally reported incidence estimates similar to ours. McGrother et al8 reported a 1-year incontinence incidence of 8% among female patients aged 40-59 years registered with 108 general practices. Two population-based studies9, 10 of women younger than age 60 years reported mean annual incidences ranging from 4% to 5%. Also, similar to our observation of a 1.8% average 1-year incidence of leaking at least once per week, Moller et al11 observed a 2.1% incidence of at least weekly incontinence during 1 year of follow-up among women aged 40-60 years.
In our study, the overall proportion of women with incontinence remission (13.9% over 2 years) was very similar to the overall proportion of women with incontinence onset between 2001 and 2003 (13.7%). Although there are very limited data on remission, Hagglund et al9 also observed similar rates of incontinence incidence (4.3% per year) and remission (4.0% per year) among 248 women aged 22-50 years. However, several studies8, 12 have reported rates of remission that are 2-3 times higher than the incidence rate. Nonetheless, these data all indicate that the majority of existing cases do not improve over the short term. Moreover, we found that a minority of our subjects with even frequent incontinence had mentioned incontinence to their physician, and just 13% received any medical or surgical treatment. These figures are similar to several previous studies of incontinence treatment and treatment-seeking behavior.13, 14, 15
Several limitations of this study should be considered. Classification of incontinence frequency and type was based on self-report. However, in a similar population of nurses, we established high reliability of reports of incontinence symptoms.5 Moreover, several studies suggest that self-reported symptoms are valid when assessing incontinence at a single time point16 and when examining changes in incontinence severity over time.17
Validation studies of self-reports of type of incontinence compared with clinical diagnoses indicate that self-reported stress and urge symptoms tend to have good specificity but low sensitivity.18, 19 These findings suggest that incidence estimates based on self-reports may somewhat underestimate stress and urge incontinence. However, we collected data on type of incontinence only from women with incontinence at least once per week, among whom it may be easier to identify precipitating circumstances.
Utilization of treatment for incontinence among the women with prevalent incontinence at baseline is unknown in our participants; however, few women in our study with incident frequent incontinence received any treatments, and other studies have found consistent data.13, 14, 15 Together these findings suggest that treatment for incontinence may explain little of the observed proportion of women who reported a decrease in leaking frequency during the study period. For example, if 20% of the women who experienced a decrease in leaking frequency from at least weekly incontinence at baseline used incontinence treatment, the proportion of women with spontaneous incontinence improvement changes from 47% to 42%.
Finally, our incidence estimates may not be generalizable to all women because our participants are a select group of largely Caucasian health professionals. However, the prevalence of many incontinence risk factors in our subjects are fairly similar to those in the general population (eg, prevalence of obesity and type 2 diabetes20, 21). In addition, our findings are consistent with the limited available incidence studies, and moreover, our estimates of incontinence prevalence22 are nearly identical to those reported in many other studies of middle-aged women.1 Thus, all of these observations suggest that the incidence estimates reported here are likely not materially different from those in broader populations of middle-aged, Caucasian women.
In conclusion, our data suggest that development of urinary incontinence is common among women aged 36-55 years; in this age group, overall, about 1 in 7 continent women appear to develop at least monthly incontinence. Incontinence is a dynamic condition in these women; however, whereas there is significant remission or regression of symptoms, we found that the majority of prevalent cases had a similar or increased frequency of leaking after 2 years of follow-up. Importantly, even within our population of health professionals, a minority of incontinent women in this age group mentioned urinary incontinence to their physician. Therefore, to identify women with incontinence, health care providers may need to initiate discussions about urinary symptoms, even among their younger patients.
References
- . Epidemiology and natural history of urinary incontinence. Int Urogynecol J Pelvic Floor Dysfunct. 2000;11:301–319
- . Epidemiology and natural history of urinary incontinence in women. Urology. 2003;62(4 Suppl 1):16–23
- . Psychosocial impact of urinary incontinence in the community-dwelling population. J Am Geriatr Soc. 1990;38:282–288
- . Urinary incontinence in adults. J Am Geriatr Soc. 1990;38:265–272
- . Association of age, race, and obstetric history with urinary symptoms among women in the Nurses’ Health Study. Am J Obstet Gynecol. 2003;189:428–434
- . Validation of a severity index in female urinary incontinence and its implementation in an epidemiological survey. J Epidemiol Community Health. 1993;47:497–499
- . Preference, compliance and initial outcome of therapeutic options chosen by female patients with urinary incontinence. J Urol. 1995;154:1727–1730
- Storage symptoms of the bladder: prevalence, incidence and need for services in the UK. BJU Int. 2004;93:763–769
- . Changes in urinary incontinence and quality of life after four years (A population-based study of women aged 22-50 years). Scand J Prim Health Care. 2004;22:112–117
- . Is incontinence associated with menopause?. Obstet Gynecol. 2001;98:628–633
- . Incidence and remission rates of lower urinary tract symptoms at one year in women aged 40-60: longitudinal study. BMJ. 2000;320:1429–1432
- . Five-year incidence and remission rates of female urinary incontinence in a Swedish population less than 65 years old. Am J Obstet Gynecol. 2000;183:568–574
- . Health care discussions and treatment for urinary incontinence in U.S. women. Am J Obstet Gynecol. 2006;194:729–737
- . Medical and self-care practices reported by women with urinary incontinence. Am J Manag Care. 2004;10(2 Pt 1):69–78
- . Factors associated with women’s decisions to seek treatment for urinary incontinence. J Womens Health. 2003;12:687–698
- . Clinical and cystometric characteristics of continent and incontinent noninstitutionalized elderly. J Urol. 1988;140:567–571
- . Validity study of the severity index, a simple measure of urinary incontinence in women. BMJ. 2001;322:1096–1097
- . Diagnostic classification of female urinary incontinence: an epidemiological survey corrected for validity. J Clin Epidemiol. 1995;48:339–343
- . Urodynamic tests for female geriatric urinary incontinence. Urology. 1990;36:431–439
- . Prevalence of overweight and obesity in the United States, 1999-2004. JAMA. 2006;295:1549–1555
- . Prevalence of diabetes and impaired fasting glucose in adults—United States, 1999-2000. MMWR Morb Mortal Wkly Rep. 2003;52:833–837
- . Risk factors for urinary incontinence among middle-aged women. Am J Obstet Gynecol. 2006;194:339–345
This work was supported in part by Grants DK62438 and CA50385 from the National Institutes of Health (NIH). M.K.T. is supported by NIH Grant R25 GM55353.
Cite this article as: Townsend MK, Danforth KN, Lifford KL, et al. Incidence and remission of urinary incontinence in middle-aged women. Am J Obstet Gynecol 2007;197:167.e1-167.e5.
PII: S0002-9378(07)00408-5
doi:10.1016/j.ajog.2007.03.041
© 2007 Mosby, Inc. All rights reserved.
Volume 197, Issue 2 , Pages 167.e1-167.e5, August 2007
