URINARY INCONTINENCE

Defining Urinary Incontinence

It is difficult to discuss urinary incontinence without discussing the definition of urinary incontinence. Various definitions have been used, depending on the goals of the definer, and according to the International Continence Society, the definition of urinary incontinence has changed in the past 25 years. In 1979, urinary incontinence was “the involuntary loss of urine that is a social or hygienic problem and is objectively demonstrable.”² By 2002, urinary incontinence became “the complaint of any involuntary leakage of urine” with further description of frequency, severity, risk factors, social and hygienic impact, and effect on quality of life.¹ These changes were made to promote treatments based on symptoms, to facilitate comparison of results in research, and to help with effective communication between researchers. The most recent definition does not require incontinence to be demonstrable; rather, a complaint of urinary incontinence is enough to support a diagnosis of urinary incontinence, allowing for the fact that each woman’s perception of her incontinence is different.

Despite approved definitions of urinary incontinence, every study uses a slightly different definition. For example, in four studies published in 2000, the prevalence of incontinence ranged from 11% to 72%.³^–⁶ This wide range probably reflects the different populations studied and the differences in definitions of urinary incontinence that were used in each study. One review found that a study with a broad definition of urinary incontinence, such as any loss of urine in a 12-month period, had a higher prevalence rate than one defining urinary incontinence over a shorter period, such as the number of episodes in the past month.⁷ When the definition of urinary incontinence in a study becomes even more specific, the result is that the prevalence numbers decrease. For example, in one study, incontinence was assessed by asking a series of detailed questions modified from epidemiologic studies, as opposed to asking just one or two questions. The result of this more detailed ascertainment was a slightly lower number of women with incontinence in the population than identified in previous studies, with only 21% of women over the age of 70 complaining of at least weekly urinary incontinence.⁸ These differences speak loudly to the need for standardized definitions of urinary incontinence to achieve a more precise assessment of the scope of the problem.

Three types of incontinence are usually assessed in survey questionnaires. Urge urinary incontinence is urine loss associated with an overwhelming urge to void associated with rushing to the bathroom and not making it there in time. These women wear a pad to go out and often limit their social schedule. Stress urinary incontinence is loss of urine caused by increased physical activity, coughing, sneezing, or laughing. These women have limited their physical activity because of their incontinence. Mixed urinary incontinence incorporates aspects of stress and urge incontinence in a woman’s complaints. Mixed incontinence is often difficult to assess until certain therapies have been attempted. For example, a woman with stress and urge symptoms may be so significantly improved with behavioral modification, pelvic floor exercises, and medication for urgency that she does not notice her stress incontinence. Most studies report a higher rate of stress and mixed incontinence compared with urge incontinence.^9,¹⁰ An analysis of the world literature reports that stress incontinence is predominant at 49%, followed by mixed incontinence at 29% and urge incontinence at 22%.¹¹

The various prevalence numbers for different varieties of incontinence also result from the inconsistent ages of populations studied and from the diverse populations evaluated. Each study has a new group of women with differences in age, ethnicity, and history such that it is difficult to generalize the results of the study to any other population. Incorrect estimates can also result from bias in data collection and underreporting due to embarrassment. In simple population surveys, most adult women report that they occasionally leak drops of urine with physical exercise, and up to 46% of community-dwelling women complain about some degree of urinary incontinence.^12,¹³ These numbers underscore the magnitude of this issue and the importance of reporting valid data.

Risk Factors

Women who exercise report more urinary incontinence. Studies by Nygaard and associates ^14,¹⁵ found that as many as 30% of women complain of urinary leakage during physical activity. The highest rate (38%) was reported in runners. The same researchers demonstrated that even among young, nulliparous women, up to 28% report incontinence with exercise.^14,¹⁵ Another study found that up to 80% of elite trampolinists reported involuntary urine leakage.¹⁶ Although this is an extreme example, it does make the point that high-impact sports lead to more urinary incontinence in women.

As our population ages, the prevalence of urinary incontinence will increase. According to the United States Bureau of Census, the number of postmenopausal women in the population will increase from 23% of the total population in 1995 to 33% in 2050, and the proportion of women older than 85 years will triple in the same period.¹⁷ In women with incontinence, the rate of stress incontinence peaks between 45 and 49 years of age and then begins to slowly decrease with further aging.³ This decrease in stress urinary incontinence may reflect the decrease in activity that usually occurs with aging, leading to a concomitant decrease in urinary incontinence. Although there is a decrease in stress urinary incontinence, the prevalence of any incontinence increases with age in a linear fashion from 3% to 34.7% in young women to 25% to 59.5% in women older than 60 years. This statistic highlights the increase in urge urinary incontinence and the prevalence of that problem later in life.

More than 70% of women living in nursing homes report urinary incontinence.¹⁸^–²⁰ Urinary incontinence reported by nursing home residents often has causes other than detrusor overactivity or hypermobility of the urethra. These women can have problems with chronic disease, decreased mobility, and medications that cause urinary incontinence.

Urinary incontinence is two to three times more common in women than in men. There is a very low prevalence of urinary incontinence in men younger than 60 years, whereas incontinence in women steadily increases starting at a much younger age. Men are very unlikely to report stress incontinence, severe incontinence, or irritative bladder symptoms. The anatomic differences between men and women and the risk factors that women face, such as childbirth and hysterectomy, cause them to have more problems with stress urinary incontinence. Men are, however, much more likely to report voiding difficulties due to prostate problems as they age and their prostates enlarge.²¹

Several studies have shown an association between childbirth and urinary incontinence.²²^–²⁴ Stress incontinence shows the strongest correlation with parity, whereas there is little correlation between parity and urgency incontinence; rather, aging is more strongly associated with this problem. Vaginal birth may directly damage the pelvic muscles and connective tissues that are necessary for pelvic floor support and for functioning of the urethra. Vaginal birth also leads to a loss of pelvic muscle strength in the immediate postpartum period that gradually returns, something not seen after cesarean section. Studies have also shown that there is an increased risk of urinary incontinence after surgical vaginal delivery compared with cesarean section that lasts for at least 3 years.²⁵ The debate over whether cesarean section prevents urinary incontinence is ongoing, with arguments from both sides and many physicians caught in the middle.

It had been thought that menopause was a risk factor for lower urinary tract symptoms and urinary incontinence. Atrophic vaginitis of menopause is associated with a multitude of symptoms, including vaginal dryness, burning, and irritation; urinary urgency and frequency; stress urinary incontinence; and recurrent urinary tract infections. The atrophy caused by estrogen deficiency is in part responsible for sensory urogenital symptoms and for the decreased resistance to infection seen in menopausal women. The value of estrogen replacement in this situation, however, is debatable. In two randomized, controlled trials of estrogen and progestin or estrogen alone versus placebo in menopausal women, there was no difference in urinary tract infection rates in the patients who received hormone therapy.^26,²⁷ In another trial, low-dose estriol reduced the frequency of urinary tract infections in menopausal women.²⁸ Another study showed that intravaginal estriol reduced the risk of recurrent urinary tract infections.²⁹ Hormone therapy for urinary incontinence has been evaluated in many randomized, controlled trials. In the Heart and Estrogen/Progestin Replacement Study (HERS), no difference was found in incontinence improvement between the hormone therapy group and the placebo group, and hormone therapy seemed to exacerbate incontinence more than the placebo group.³⁰ Another randomized trial also demonstrated no difference between the estrogen group and the placebo group for improvement of stress urinary incontinence.³¹ In a trial of estrogen for urgency incontinence, there was no difference between the hormone group and the placebo group.³² The conclusion can be made that frequent urinary tract infection in menopausal women can be treated with intravaginal estrogen if there is an element of atrophy involved with the bladder infection.

Obesity and hysterectomy have been thought to be risk factors for urinary incontinence, although much of the evidence is conflicting. Obesity is more common in women with urinary incontinence than in continent women. It is possible that obese women have higher intra-abdominal pressures that overwhelm the continence mechanism. Weight loss has been shown to improve incontinence that is primarily stress related.³³^–³⁸ Hysterectomy has been associated with incontinence in some observational studies, but in others, there was no difference between women who had had a hysterectomy and those who had not had surgery.^24,^39,⁴⁰