Urinary incontinence and major depression are prevalent, distressing illnesses that disproportionately affect women.1,2 During their lifetimes, approximately one half of all women will develop urinary incontinence,1 and 21% will have one or more episodes of major depression.2 Both disorders are associated with social stigma, underreporting by patients, and lack of recognition by physicians.3–6 Incontinence has been associated with significant decrements in function and quality of life7–9 and has a societal cost to the United States of $26.3 billion annually.10 Major depression has been shown to have a marked effect on both social and vocational functioning, with increased disability, lost productivity, and excess mortality.11–13 Major depression is now recognized as a leading cause of disability worldwide14 and has a societal cost to the United States of $83.1 billion annually.15 Comorbid depression may further amplify the embarrassment and shame caused by incontinence, leading to increased social avoidance.9
Several researchers have suggested a possible link between depression and urinary incontinence,9,16–21 but the relationship between these disorders is not well understood. Each of these studies was limited by being conducted in clinical settings,9,17–19,21 surveying limited age ranges,16,20 or employing depression symptom screens rather than structured psychiatric interviews or survey instruments based on major depression criteria.19–21 None of these studies examined the factors associated with comorbid major depression in community-dwelling women with incontinence, which is critical because women frequently delay or do not seek medical care for both disorders.3–6 It is also not known how psychiatric comorbidity impacts symptom perception, quality of life, and functional impairment associated with incontinence in community-dwelling women.
Additional information is needed about the prevalence and potential impact of comorbid major depression and urinary incontinence using large samples and major depression diagnostic criteria. This study's objectives were to estimate the prevalence of and sociodemographic and clinical factors associated with comorbid major depression in incontinent women aged 30–90 years.
MATERIALS AND METHODS
The participants in this 2002 study were women enrolled at Group Health Cooperative, a health maintenance organization serving approximately 550,000 individuals in Washington state. Group Health Cooperative enrolls 1 in 10 Washington residents and provides traditional group and individual care plans, as well as Medicare, Medicaid, and government employee coverage. A 15-page self-report form was mailed to an age-stratified random sample of 6,000 Group Health Cooperative female enrollees, aged 30–90 years. The sample was stratified by decade of age, with oversampling for the younger decades to ensure a sufficient number of respondents with incontinence in each age group. The survey contained questions about medical, surgical, obstetric, and gynecologic history, medications, bladder symptoms, depressive symptoms, functional status, quality of life, and demographic characteristics. Exclusion criteria were death, inability to locate the prospective participant, disenrollment from Group Health Cooperative, paralysis, severe mental or physical barriers to completing a written questionnaire, and current urinary tract infection. An initial questionnaire and 2 reminder questionnaires were sent. A $3 gift certificate to a local store was included in the initial mailing to encourage response. The sample was linked to Group Health Cooperative longitudinal automated data, including inpatient and outpatient diagnoses, pharmacy purchases, and health care utilization in the year preceding questionnaire return. Automated data were available for respondents and nonrespondents. All participants provided informed consent, and the study was approved by the Group Health Cooperative Human Subjects Committee.
Frequency of urine loss was characterized as less than once a month, 1 to several times per month, 1 to several times per week, 1 or 2 times per day, or 3 or more times per day. Amount of urine lost was quantified as a few drops, a small amount, a moderate amount, or a large amount. Urinary incontinence was defined as leakage of any amount that occurred at least monthly. Stress incontinence symptoms were defined as leaking or losing urine during activities like coughing, laughing, or walking. Urge incontinence symptoms were defined as leaking or losing urine associated with such a strong and sudden urge to urinate that one could not reach the toilet fast enough. Subjects were classified as having mixed incontinence symptoms if they answered affirmatively to both stress and urge symptoms. These questions were modeled after the Norwegian EPINCONT study.22
To characterize the degree of incontinence, we used the Sandvik severity index.23,24 To create the index, we aggregated responses into 2 amount levels: 1) few drops/small amount, and 2) moderate/large amount; and 4 frequency levels: 1) less than monthly, 2) monthly, 3) weekly, and 4) daily. The index value (1–8) was calculated by multiplying the amount (2 levels) by the frequency (4 levels) of leakage, yielding categorical variables of mild (1–2), moderate (3–4), and severe (6–8). This widely used index has been validated against pad-weighing tests23,24 and in independent populations.25
The study measured quality of life with the Incontinence Quality of Life Instrument (I-QOL), a validated 22-item self-report measure for incontinence-specific quality of life. The instrument yields a total score and 3 subscale scores for avoidance and limiting behaviors, psychosocial impacts, and social embarrassment.8 The perceived severity of incontinence symptoms was measured by the Patient Incontinence Severity Assessment (PISA), a self-report item that asks subjects to rate their incontinence severity on a 5-point Likert scale, ranging from 1 (mild) to 5 (severe). This item has been shown to correlate well with a physician assessment of incontinence severity and a validated severity index.26
The PRIME-MD Patient Health Questionnaire, 9-item (PHQ-9) was used to diagnose current major depression.27 The PHQ-9 conforms to the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) criteria for major depression and has excellent agreement with diagnosis of major depression based on structured psychiatric interview.27 The criteria for major depression required the patient to have, for at least 2 weeks, 5 or more depressive symptoms present for more than half of the days, with depressed mood or anhedonia at least one of these symptoms.27,28
The categorical variables of race, ethnicity, level of education, income, employment, smoking, and alcohol use were assessed by self-report. Self-reported height and weight were used to calculate body mass index (BMI) in kg/m2, which was categorized as normal (< 25 kg/m2), overweight (25–29 kg/m2), and obese (≥ 30 kg/m2). Two detailed questions on menstrual cycles and cessation of menses were used to determine menopausal status.
Group Health Cooperative automated pharmacy data were used to generate the RxRisk chronic disease score, a measure of medical comorbidity based on prescription drug use over the previous 12 months.29 Medical comorbidity was dichotomized according to median split of the RxRisk score.
The presence of diabetes mellitus, which has been associated with both incontinence and depression, was determined from Group Health Cooperative's automated data by any of the following: taking a diabetic agent, fasting glucose more than 126 mg/dL confirmed by a second out-of-range test within 1 year, random glucose more than 200 mg/dL confirmed by a second out-of-range test within 1 year, or a hospital discharge diagnosis or 2 outpatient diagnoses of diabetes.30 Group Health Cooperative automated data were also used to obtain each subject's age, which was used as a continuous covariate in the logistic regression analysis.
The questionnaire also included the World Health Organization Disability Assessment Schedule II (WHO-DAS II), a functional status measure that assesses level of disability across various conditions and interventions, reported as a continuous score.31
Descriptive statistics were used to characterize the overall sample. Prevalence rates of incontinence were calculated for the study population according to decade of age. An age-weighted overall prevalence of incontinence was also calculated, according to the age distribution of the Group Health Cooperative total female population. Prevalence rates for incontinence severity and symptom type subgroups were also estimated.
Prevalence rates of major depression were calculated for the overall sample and subgroups according to presence, severity, and type of incontinence. Bivariate comparisons of variables by major depression status were conducted in the subset of women with incontinence, using χ2 tests for categorical variables and t tests for continuous variables. Also, t tests were used to examine differences in PISA, I-QOL, and WHO-DAS II scores between groups based on the presence or absence of major depression. General linear models were used to examine differences in I-QOL and WHO-DAS II scores between groups based on the presence or absence of major depression, controlling for incontinence severity.
Using factors determined a priori and significant factors from the bivariate analyses, we created a series of multivariate logistic regression models to predict the odds of having major depression among women with incontinence. In the first stage, age and medical comorbidity were included. In the second stage, variables associated with major depression (P < .1) in the univariate analyses (BMI, education, smoking, incontinence severity, and diabetes) and variables determined a priori (incontinence type) were added individually to the model. In the third stage, the variables that were significantly associated with major depression in the second stage (P < .05) were added simultaneously. Adjusted odds ratios were derived for the probability of major depression, given the presence of specific covariates and controlling for the other covariates. All statistical analyses were performed using SAS 8.2 (SAS Institute, Cary, NC).
To assess potential response bias, we examined differences between survey respondents and nonrespondents by using the automated database. We estimated the probability of being a respondent as a logistic function of the following predictor variables: age, RxRisk score, number of primary care visits in the past year, mood disorder diagnosis, and diabetes diagnosis. We then applied a weighted analysis with weights inversely proportional to the estimated probability of response.32 In this type of analysis, persons with a low probability of responding are given a higher weight in the analysis to represent the larger number of nonrespondents with similar characteristics. We compared weighted and unweighted analyses to see if postsurvey adjustment for factors related to nonresponse resulted in meaningful differences in survey estimates. Differences in weighted and unweighted data were negligible; therefore, we report analyses based on observed data.
Details of the response rate and the incontinence characteristics of the sample are described in detail elsewhere.33 Briefly, the response rate was 64% (n = 3,536), and respondents were older (53.4 versus 47.7 years; P < .001), had higher RxRisk comorbidity scores (2,293.9 versus 2,102.4; P = .002), and were less likely to have an International Classification of Diseases, 9th Revision (ICD-9) mood disorder code in the past year (6.2% versus 7.9%; P = .03) than were nonrespondents. There were no differences between respondents and nonrespondents in number of primary care visits (3.5 versus 3.3; P = .06) or presence of an ICD-9 urinary symptoms code (2.8% versus 2.8%; P = .999) in the past year. The prevalence of urinary incontinence (any leakage that occurs at least monthly) among respondents was 42% (n = 1,458), and prevalence increased nearly linearly with age, from 28% in the youngest decade to 55% in the oldest decade. Among respondents, 9% (n = 293) reported mild incontinence, 15% (n = 523) reported moderate incontinence, 18% (n = 624) reported severe incontinence, and 58% (n = 1,980) reported no incontinence. The prevalence of severe incontinence increased markedly with age, with only 8% of 30–39 year olds reporting severe incontinence compared with 33% of 80–90 year olds. One-third of incontinent women reported stress incontinence symptoms only, 13% reported urge incontinence symptoms only, 50% reported mixed incontinence symptoms, and 4% had unknown symptom types. The prevalence of stress incontinence symptoms decreased with age, and the prevalence of urge and mixed incontinence symptoms increased with age. Because of the small number of individuals with urge symptoms only, those with urge incontinence and mixed incontinence were combined into an urge incontinence component subgroup for further analyses.
The prevalence of major depression among respondents was 3.7% (n = 129), with 2.2% (n = 43) in those without incontinence and 6.1% (n = 86) in those with incontinence. Prevalence differed significantly according to incontinence severity and type, with a higher prevalence of major depression in respondents with moderate and severe incontinence and those with an urge incontinence component (Figs. 1,2).
In the subset of women with incontinence, depressed and nondepressed women differed significantly in many demographic and clinical respects (Table 1). Depressed women had a higher BMI, lower educational attainment, and lower income and were more likely to be current smokers. They were also more likely to have severe incontinence.
Table 2 shows the adjusted odds ratios for major depression from the final logistic regression model. Obesity (BMI ≥ 30), lower educational attainment, current smoking, moderate incontinence, and severe incontinence were each associated with increased odds of having major depression, controlling for age and medical comorbidity.
Women with major depression perceived their incontinence symptoms as significantly more severe than nondepressed women (PISA scores: 2.7 versus 2.0; P < .001). Women with major depression reported significantly lower incontinence-specific quality of life on the I-QOL Total (65.0 versus 83.5; P < .001), Avoidance and Limiting Behaviors (61.2 versus 77.4; P < .001), Psychosocial Impact (73.3 versus 91.1; P < .001), and Social Embarrassment (53.4 versus 76.7; P < .001) scales (Fig. 3). Women with major depression also reported significantly greater functional impairment (WHODAS 41.5 versus 14.0; P < .001). Interactions between major depression and incontinence severity were examined, and significant differences in quality of life and functional status scores remained (Tables 3 and 4).
In this study, the prevalence of current major depression in a random sample of women enrolled in a large health maintenance organization was 3.7%, which is consistent with other large community-based samples.2 Major depression was 3 times more prevalent in women with urinary incontinence than in continent women (6.1% versus 2.2%). We showed a strong association between severity of incontinence and current major depression, which persisted after adjusting for established major depression risk factors like obesity, smoking, medical comorbidity, and lower educational attainment.34,35 Women with moderate or severe incontinence were 3 times more likely to have current major depression than women with mild incontinence, after adjusting for these other factors.
There is a growing body of evidence showing an association between depression and urinary incontinence, including a few studies using depression diagnostic tools rather than symptom screening measures.9,16,17 This distinction is important because it reveals that many women with incontinence have serious forms of depression that are often undiagnosed or undertreated. The relationship between major depression and incontinence is likely bidirectional. The symptoms and functional impairment associated with a chronic illness like incontinence may lead to depression.36 Alternately, depression and altered neurotransmitter function could affect the bladder's complex regulation, leading to the development of uninhibited detrusor contractions and urge incontinence.21 In fact, recent pharmacologic agents effective in treating both depression and urinary incontinence have been indentified.37
Identifying major depression in patients with other medical illnesses is essential, not only because depression causes significant symptomatic distress, but also because it may adversely impact other disease processes. Comorbid major depression is known to produce heightened focus on the adverse physical symptoms associated with other chronic diseases, such as pain and fatigue.38,39 Patients with major depression may also manifest additive disability and impaired self-care (ie, diet, exercise, taking medications) required for chronic illness care.40–43 A recent meta-analysis showed that medically ill patients with major depression had 3 times greater odds of nonadherence to medical treatment recommendations than nondepressed medically ill patients.44 When controlling for age, gender, and severity of medical illness, the direct medical costs of depressed patients with chronic medical illness are approximately 50–70% higher than those of nondepressed patients.45,46
In this study, depressed subjects reported significantly higher incontinence symptom severity, significantly lower incontinence-specific quality of life, and significantly greater functional impairment than nondepressed subjects. These results mirror our result in a specialty clinic population, where depressed patients exhibited similar findings.9
Major depression can be effectively treated in the setting of a medical comorbidity, with recovery rates comparable to those of patients with major depression not complicated by medical illness.47 A recent study of patients with osteoarthritis and major depression or dysthymia showed that more effective treatment of depression was associated with decreased burden of physical pain, improved functioning, and increased quality of life.48 Thus, the screening and treating of incontinent women for major depression may not only lead to improvements in their mood disorder, but may also lead to greater adherence to medical treatments and improved incontinence outcomes.
Our sampling strategy, use of a depression diagnostic measure, and links to automated medical data, which provide accurate assessment of comorbid medical conditions, are strengths of this study. The comprehensive data collected and the large number of participants allow for analysis of many potential risk factors. Our response rate may be a limitation, because women with severe depression may be less likely to participate in a mailed survey. Another limitation is the cross-sectional study design, which measures prevalence, not incidence, thereby limiting information about onset of disease and natural history. The cross-sectional design also prevents determination of the causal relationships between major depression and associated risk factors, like incontinence severity. Longitudinal studies to help clarify directionality and causality are warranted.
Women must be encouraged to think of urinary incontinence and major depression as treatable medical disorders, not as stigmatized conditions that should remain hidden. Practitioners should query women of all ages about symptoms of these prevalent diseases and offer treatment for either one or both when detected. In women with urinary incontinence, special attention should be paid to incontinence severity, obesity, smoking, and lower educational attainment as potential risk factors for major depression.
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