Clinical Impact of Overactive Bladder

Abstract

Overactive bladder (OAB) is a medical condition with the symptoms of urinary frequency and urgency, with or without urge incontinence. Traditionally, epidemiologic studies have focused on the symptom of incontinence, and therefore the prevalence and clinical impact have been grossly underestimated. Recently, several population-based studies have been conducted that have provided insight into the true magnitude of OAB. This article will review the latest data on the prevalence of OAB and discuss the impact of the condition on quality of life. Furthermore, it will examine some of the comorbidities associated with OAB and look at the potential economic impact of OAB.

Overactive bladder (OAB) is defined as a medical condition having the symptoms of urinary frequency (>8 micturitions/24 hours) and urgency, without or without urge incontinence, in the absence of local pathologic or metabolic factors that would account for these symptoms.¹ Previous estimates of the number of people suffering from OAB have been on the order of 17 million in the United States² and between 50 and 100 million worldwide.¹ However, recent studies suggest that the prevalence of OAB may actually be higher. In the past, most epidemiologic studies in selected populations have underestimated the prevalence of OAB, because they focused only on those patients with incontinence. Also, because these studies focused mainly on the symptom of urge incontinence and not the more common symptoms of frequency and urgency, epidemiologic evidence regarding the individual and societal impact of OAB varied considerably. However, it is now known that symptoms of frequency and urgency, even in the absence of incontinence, can have a profound effect on quality of life. Recent studies have concentrated on determining the prevalence of OAB with or without incontinence. These studies have confirmed the observation that the prevalence of OAB, like that of incontinence, is higher in women than in men and increases with age. As a result of new data on the prevalence of OAB and its impact on quality of life, there has also been a conscious effort to increase public awareness of the condition and to encourage sufferers to seek medical attention.

Prevalence of OAB

Two major studies sponsored by Pharmacia Corporation were conducted in Europe and the United States to examine the prevalence and impact of OAB.

European Population-Based Study

Milsom and colleagues reported the results of a large-scale study to determine the population-based prevalence of OAB symptoms among men and women aged 40 and older from six European countries (France, Germany, Italy, Spain, Sweden, and the UK).³ Telephone surveys (except in Spain, where direct interviews were conducted) of 16,776 people were carried out by the Sifo/Gallup network. A random sample was obtained by a stratified approach based on geographic variables. At least 300 individuals with OAB symptoms were interviewed in each country. The questionnaire involved a two-stage screening procedure that first identified people with bladder control problems and then characterized the nature of the condition. Symptoms attributable to OAB were identified by responses to questions on frequency, urgency, and urge incontinence. Frequency was defined as more than eight voids/day. The second stage included respondents aged 40–74 years and consisted of questions pertaining to the duration of symptoms, treatments, and the influence of the disorder on their daily lives. Overall, 16.6% of the respondents had symptoms attributable to OAB, that is, frequency, urgency, and urge incontinence either alone or in combination.³ Frequency was the most commonly reported symptom in the OAB group (85%), followed by urgency (54%) and urge incontinence (36%). The prevalences of different symptom combinations are shown in Figure 1. The prevalence of OAB increased with increasing age and was similar in men and women (Table 1). The vast majority of people (79%) had symptom durations of at least 1 year, and 49% had symptoms for more than 3 years.

Figure 1.

Prevalence of different OAB symptoms, from a European population-based prevalence study. Reprinted from Milsom et al,³ with permission.

Table 1.

Prevalence (%) of OAB Symptoms, Grouped According to Age and Gender, from a European Population-Based Prevalence Study

Age (y)	Men (n = 7048)	Women (n= 9728)
40–44	3.4	8.7
45–49	6.0	10.6
50–54	9.8	11.9
55–59	13.2	16.9
60–64	18.9	16.9
65–69	23.7	17.5
70–74	22.3	22.1
≥75	41.9	31.3
All	15.6	17.4

Data from Milsom et al.³

The NOBLE Program

A similar prevalence study was undertaken in the United States. The National Overactive Bladder Evaluation (NOBLE) Program was conducted to establish estimates of the prevalence of OAB and of the individual burden of the illness, and to explore differences between continent and incontinent sufferers of OAB.⁴ In the NOBLE study, a validated, computer-assisted telephone interview used a quota sampling method to select 5204 English-speaking adults over 18 years of age, representative of the U.S. noninstitutionalized population with regard to gender, age, and geographic region. “OAB dry” was defined as at least four episodes of urgency in the preceding 4 weeks and either frequency of more than eight voids/day or the use of one or more coping behaviors to control bladder function. “OAB wet” included the same criteria plus at least three episodes of urinary incontinence (UI) in the preceding 4 weeks that could not be attributed to stress incontinence. The overall prevalence of OAB in the NOBLE study was 16.9% in women and 16.0% in men. As in the European study, the prevalence of OAB increased with age. The prevalence of OAB wet was greater in women than in men (Table 2).

Table 2.

Prevalence of OAB in the U.S. According to Gender, from the NOBLE Study

	Men	Women
OAB total (%)	16.0	16.9
OAB wet (%)	2.6	9.3
OAB dry (%)	13.6	7.6

OAB total represents all respondents with OAB symptoms and OAB wet and dry those individuals with OAB with and without incontinence, respectively. Data from Stewart et al.⁴

Conclusions

Until recently, data on the prevalence of OAB were scarce and were acquired predominantly from studies on incontinence. Although conducted using slightly different methods, the European and NOBLE studies, the first comprehensive studies on the prevalence of OAB in industrialized nations, drew similar conclusions. The overall prevalence of OAB symptoms was 16%–17%, with a little more than one third of respondents having incontinence. The prevalence of incontinence among OAB sufferers is considerably higher in women than in men.

Impact of OAB on Quality of Life

OAB can have a profound effect on quality of life. It can have an impact on even simple daily activities, such as work, travel, interpersonal activities, physical activity, sexual function, and sleep.⁵

As with the prevalence literature, many previous studies focused specifically on the symptom of urge incontinence and its effect on quality of life, without specific attention paid to frequency and urgency. For example, using a self-administered generic questionnaire assessing quality of life (Short Form 36, SF-36), patients who suffer from OAB with urge incontinence were found to have a lower quality of life in the social and functional domains than patients with diabetes.^6–8 In a questionnaire surveying the prevalence of UI and its effect on quality of life, Simeonova and colleagues showed that women with incontinence reported a poorer quality of life than continent women.⁹ In addition, women with urge incontinence or mixed incontinence reported a statistically significant poorer quality of life than those with stress incontinence. The same can be said for men. Brocklehurst reported that 36% of incontinent respondents (from a random sample of 1883 men at least 30 years old) believed that the symptom affected their lifestyle a great deal or a fair amount and only 23% believed that it had no effect.¹⁰

Although the effects of incontinence are probably the most dramatic, the effects of frequency and urgency cannot be ignored. In the European study by Milsom and coworkers, 65% of men and 67% of women with OAB (with or without urge incontinence) reported that their symptoms had an effect on daily living.³ Of persons between the ages of 40–74, 60% consulted a practitioner about their symptoms. Interestingly, almost as many respondents with frequency and urgency alone (59%) sought help as did those with incontinence (66%). Data from the NOBLE study showed that men and women with OAB wet or with OAB dry had clinically and statistically significantly lower quality of life (SF-36 subscores), lower depression status (higher Center for Epidemiologic Studies Depression Scale scores) and poorer quality of sleep (higher Medical Outcomes Study sleep scores) than did controls after adjusting for comorbid illnesses.⁴ Those with OAB wet and those with OAB dry had similar scores on all these scales.

Liberman and associates recently conducted a large U.S. community-based survey on the effect of OAB symptoms on health-related quality of life.¹¹ They used a telephone survey, and households were contacted at random. An age-stratification scheme was used to generate age strata of specified size: 18–49 years old (20%), 50–64 years old (40%), and 65 and older (40%). Respondents identified as having symptoms of OAB were subdivided into OAB wet and OAB dry, as described above for the NOBLE study. A random sample of individuals was then chosen to receive a follow-up mailed questionnaire to assess quality of life using the Medical Outcomes Study-Short Form 20 (SF-20). After adjustment for confounders, both OAB groups had lower quality of life scores in every domain (physical functioning, role functioning, social functioning, mental health, health perception, and bodily pain). These differences were statistically significant for all six domains in the OAB wet group, for five of the domains in the OAB total group, and for three of the domains in the OAB dry group. The greatest impact occurred among individuals with both frequency and urgency and among those in the frequency-only subgroup who had more than 10 micturitions daily. For those with the single symptom of frequency (8–10 micturitions/day) or urgency, symptoms were milder and, although quality of life scores were lower, did not reach statistical significance. In the OAB total group, the domain with the greatest difference compared to controls was general health perception (23.1% lower). General health perception was also the most affected domain for the OAB wet group (33.4% lower than in controls) and the OAB dry group (16.5% lower than in controls).

Conclusions

OAB can have a significant effect on quality of life. The impact of incontinence has been well documented; however, recent studies using validated questionnaires have confirmed that OAB without incontinence also influences quality of life in a negative way.

Comorbidities Associated with OAB

Not only do OAB and associated incontinence diminish overall quality of life, but their presence can also create additional health problems for the sufferer. These include an increased risk of falls and fractures, urinary tract and skin infections, sleep disturbances, and depression.¹²

Falls, Fractures, and Infections

Some studies have identified urinary urgency and urge incontinence as predictors of recurrent falls and fractures in the elderly. One study found that the odds ratio of a hip fracture in urinary-incontinent elderly women was twice that in the general population. ¹³ Another study found that women with weekly urge incontinence had a 26% greater risk of sustaining a fall and a 34% greater risk of fracture. ¹⁴ When incontinence occurred daily, these risks increased to 35% and 45%, respectively.

Urinary tract and skin infections have also been found to occur frequently in patients with OAB and incontinence and to increase the cost of its treatment.¹⁵ However, after diagnosis and treatment, the cost of services has been shown to decline.¹²

Nocturia

Nocturia, defined as needing to get out of bed to urinate at least two times during the night, is a symptom commonly associated with OAB. People with nocturia may report lack of energy, chronic fatigue, and difficulty performing daily activities. Nocturia has been shown to correlate with reduced quality of life, disturbed sleep, and poor health.^16–18 Nocturia has many different causes, including nocturnal polyuria, which is independent of OAB. Therefore, it cannot be assumed that nocturia is always caused by OAB. However, in cases where there is a clear association, treating OAB may reduce nocturia.

Depression

Zorn and colleagues have recently suggested that there is a strong association between depression and urge incontinence.¹⁹ They prospectively evaluated 115 consecutive newly incontinent patients (and 80 controls), all of whom were questioned about a history of depression and completed a self-administered Beck Depression Inventory. Incontinent patients were equally divided among those having stress, urge, and mixed incontinence. The prevalence of depression was highest among patients with idiopathic urge incontinence (60%) and those with mixed incontinence (44%), which exceeded controls (17%), patients with stress incontinence (14%), and those with urge incontinence associated with neurologic disease (8%) or bladder outlet obstruction (33%). Patients with urge incontinence were more likely to have depression as a risk factor than controls (P = .01), and in patients with idiopathic urge incontinence the relationship was the most marked (P < .001). Such a statistically significant relationship was not seen with depression and stress incontinence or urge incontinence associated with neurologic disease or obstruction. The authors concluded that the fact that patients with stress incontinence were no more likely to be depressed than controls suggests that the relationship between depression and urge incontinence is not merely a likelihood.

Conclusions

Recent studies have suggested strong associations between OAB and several comorbid conditions, including falls and fractures, urinary tract and skin infections, sleep disturbances, and depression. It is likely that these relationships negatively affect morbidity and quality of life.

Economic Impact of OAB

Three types of “costs” determine the economic burden of any disease: direct costs, indirect costs, and intangible costs.²⁰ Direct costs include routine care, treatment, diagnostic, and consequence costs. Indirect costs are those incurred from lost wages to patients and caregivers and lost productivity as a result of mortality. Intangible costs consist of the value of pain and suffering and the decreased quality of life associated with an illness.²⁰ As one can imagine, determining the economic burden of OAB is a difficult task, especially with respect to indirect and intangible costs. To date, most studies have focused on the economic burden of UI, which is only one symptom of the OAB complex. In 1995, Wagner and Hu estimated that the costs associated with UI in the U.S. totaled $26.3 billion, or $3565 per incontinent individual.¹⁵ Because a significant number of people suffer with OAB without incontinence, it is likely that the economic burden of OAB is significantly greater than that of incontinence.²⁰ The determination or quantification of the total economic burden of OAB specifically will be instrumental in determining the allocation of resources to treat this very common condition.

Main Points.

• The prevalence of overactive bladder (OAB) has been underestimated because most surveys focus only on patients with incontinence.

• OAB, like urinary incontinence (UI), increases with age.

• The prevalence of incontinence among OAB sufferers is considerably higher in women than in men.

• Patients with OAB have significantly reduced quality of life even without UI.

• OAB and UI are associated with comorbidities like increased risk of falls and fractures, urinary tract and skin infections, sleep disturbances, and depression.