Who develops incontinence, and why?

Summarized by Robert W. Griffith, MD
December 15, 2000 (Reviewed: February 17, 2003)

Introduction

We don't know as much about incontinence as we should like to. Some experts have recently summarized what we do know about the risk factors and possible causes of the condition. (Their review includes discussion of bed-wetting in children and urinary incontinence in men, but these aspects are not considered further here.)

Epidemiology is the study of the 'distribution and causation of disease', in other words, who gets it, and why. The International Continence Society has defined urinary incontinence (UI) in women as "a condition where involuntary loss of urine is a social or hygienic problem and is objectively demonstrable". But describing the problem in terms of the social or hygienic problem is not quite enough. To start with, we need to know more about how common UI is in different groups of women.

How common is the problem?

To get an idea of how many people suffer from any sort of urinary loss at all, the authors of the review analyzed 13 studies of women from the general population. They found that 20 to 30% of women in young adult life had some degree of urine leakage, which increased to 30 to 40% around middle age, and then increased again in the elderly (ranging from 30% to 50% in different studies).

There are different sorts of incontinence: Stress incontinence is when there is urine loss on coughing, sneezing or laughing. Urge incontinence is when there is a strong desire to urinate, frequent urination, getting up at night, and the person cannot get to the bathroom in time. Mixed incontinence is a mixture of these two types. In the studies reviewed, 40% of all incontinent women were classed as having stress incontinence, 17% had urge incontinence, and 34% had mixed incontinence. Urge incontinence is more common as women get older.

When these rates are compared with the actual types diagnosed after full laboratory tests done by a urologist, stress incontinence is more frequent (about 75%), with urge and mixed incontinence less frequent (about 10-13% each).

Attempts are usually made to determine the severity of UI. Incontinence diaries are used to report the frequency and amount of each episode, whether clothes are soaked, the pads required, and so on. In spite of various ways of measuring severity, there is general agreement that, overall, severe incontinence is seen in 4% to 8% of the total number of affected women. If the nuisance value of the problem is included, as many as 20% of incontinent women - which is about 6% of all adult women - need treatment for their condition.

It should be noted, however, that up to a third of women with UI seem to get better without treatment, over time, but these are probably the less severe cases.

White women are more susceptible to UI than black women. This finding is based on a number of studies from different countries, but it must be remembered that there are different health systems and standards of care in different countries, and the wish to seek help for a condition is often a matter of local custom.

Risk factors for incontinence in women

There are several well-established risk factors for UI, allowing one to recognize if one is at increased risk of developing the condition. The main ones are:

• Age - UI increases progressively with age, the frequency roughly doubling between 45 and 85 years of age.
• Pregnancy - UI is common in pregnant women (30% to 60%) but it usually gets better after delivery. However, older women will often associate the onset of their incontinence with a pregnancy.
• Childbirth - delivery of a child can lead to slack pelvic floor muscles due to weakening and stretching. This may be worse if any of the nerves are damaged, as these control the muscles that can close off the flow of urine. Sometimes tears in the vagina or an episiotomy (a deliberate cut) during childbirth may be responsible. The number of pregnancies is sometimes thought to increase the risk for incontinence, but this is not proven.
• Menopause - this event is associated with thinning and drying of the genital tissues, which allow an increased likelihood of a bladder infection. The fact that these changes can be reversed with hormone treatment, and that there are many cases of UI that improve with estrogens, indicates that menopause is indeed a time of increased likelihood of development of UI.
• Hysterectomy - removal of the uterus is sometimes done together with removal of the ovaries, in which case there is a surgically induced menopause. Just removing the uterus alone can cause damage to the nerves of the pelvis, which can lead to an increased risk of incontinence.
• Obesity - the added weight carried by the obese can bear down on pelvic tissues, causing a chronic strain, with stretching and weakening of the pelvic floor muscles. Weight loss has been shown to decrease the severity of UI.
• Bladder infections - these are a clear cause of incontinence, but they can usually be treated effectively, and the problem resolves.
• Poor mobility - people who have difficulty getting to the toilet may be incontinent, unless they regularly receive assistance. Sometimes UI is related to such difficulties, but at others it is due to general old-age frailty, or to an age-related illness.
• Alzheimer's - people with Alzheimer's or other forms of dementia - both men and women - often have an increased risk of incontinence.
• Other factors - although not proven, factors such as constipation, taking 'water pills' and other medicines, prolapse of the uterus, and cigarette smoking have all been accused of being related to incontinence. However, good evidence is lacking for most of these.

What can be done?

It seems clear that each of the recognized risk factors can be addressed in some way, if the actual mechanism underlying UI is identified. Very often, behavioral and physiotherapy treatments can prevent incontinence from occurring in some one at higher risk (e.g. age, difficult childbirth, hysterectomy). Alternatively, they can prevent the progression from a mild case to a severe case. The authors of the review suggests that better, longer studies are needed to be able to say more exactly what the risk factors are, and how they can best be tackled.

Source

• Epidemiology and natural history of urinary incontinence. S. Hunskaar, EP. Arnold, K. Burgio, Int Urogynecol J , 2000, vol. 11, pp. 301--319

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