Urinary incontinence - Why it happens in women

Urinary incontinence

Types of incontinence and why it happens
Incontinence is leakage of urine from the bladder. It can happen to anyone at any age, but is more common in women. The idea that it affects only the elderly is completely out of date – the popularity of active sports, such as jogging, has caused more younger women to notice the problem.

What type of incontinence do you have? There are two main types of incontinence – ‘stress incontinence’ and ‘overactive bladder’ (urge incontinence). Many women have both types together and this is called ‘mixed incontinence’. Look at the box below to see what type you have. About 1 in 4 women with incontinence of urine also have faecal incontinence (Obstetrics and Gynaecology 2002;100:17–23).

Questions to ask yourself	Stress incontinence	Overactive bladder	Mixed incontinence
Do you go to the toilet to pass urine more than 7 times a day?	No	Yes	Sometimes
Do you go to the toilet to pass urine more than once during the night?	Not usually	Most nights	Most nights
Do you ever have to hurry to reach the toilet in time (for urine)?	No	Yes	Yes
Do you ever not reach the toilet in time (for urine)?	No	Often	Often
Do you ever leak urine when you laugh, sneeze, cough, run or jump?	Always	No	Always
If you leak urine, is it just a drop or is it sometimes quite a bit more?	Small	Large (usually)	Large
Are you able to hold your urine alright, but you need to pass it more than 7 times a day, in small or large amounts each time?	See your doctor, because you might have a urine infection (small amounts) or diabetes (large amounts and you are thirsty).

Reasons for stress incontinence. Leakage of urine when you cough, laugh or bend over, or with exercise such as jumping or jogging, is called stress incontinence. It is most common in young women (25–49 years of age). It occurs if the muscles at the neck of the bladder are not strong enough to hold the urine in when the pressure in the abdomen is increased (as happens when you laugh or cough). No one knows exactly why these muscles may become weak; some women notice the problem after childbirth or the menopause. Women with stress incontinence often have leakage of urine during sex, usually at penetration (when the penis enters).

Genes are now thought to be a very important cause of stress incontinence, which explains why this type of incontinence tends to run in families (Obstetrics and Gynecology 2005; 106: 1253–8). Because of their genes, some women are born with a weak pelvic floor. It is probably a weakness of collagen, the tiny strengthening fibres of muscles.

Childbirth is probably an important cause of stress incontinence. The actual birth is mostly responsible, not just the pregnancy – women who have had Caesarean sections do not usually develop incontinence later. It seems that the nerves can be stretched and bruised during the delivery, and they are unable to make the pelvic floor work after the birth. As a result, the muscles become lazy and weak. However, some research suggests that women who have had children are not more likely to have incontinence (Obstetrics and Gynecology 2005; 106: 1253–8), so it seems that more research is necessary.

Hysterectomy. A woman who has had a hysterectomy is more likely to develop incontinence in middle age than a woman who has not had the operation.

Menopause may be another reason, perhaps because the lowering levels of oestrogen make the pelvic floor muscles less efficient. However, recent research shows that although the likelihood of incontinence increases in middle-age, the hormone changes of the menopause may not be the cause. The reason may be that middle-aged women are more likely to be overweight and to have had a gynaecological operation, such as a hysterectomy.

High impact sports, such as jogging on hard pavements, are probably not good for the pelvic floor. Sports such as swimming and cycling are fine. Interestingly, women parachutists in the US Air Force have developed incontinence because the impact of landing has damaged their pelvic floor.

Lifting heavy objects strains the pelvic floor. If you have to lift anything heavy (such as a baby or small child!), get into the habit of doing it in the right way. Place your feet firmly apart in the walking position, and bend at the knees and hip but keep your back straight. Tighten your pelvic floor muscles, hold the heavy object close to you and then lift by straightening your legs.

Obesity. Being overweight is a major cause of incontinence. It puts stress on the pelvic floor muscles.

Smoking 20 cigarettes/day (now or in the past) doubles your likelihood of urinary incontinence – another reason for never smoking.

Drugs can relax the pelvic floor around the ring of muscles at the neck of the bladder, making leakage more likely. The most common culprits are some blood pressure medications (particularly alpha-blockers such as prazosin and doxazosin). If your incontinence problem seems to be related to starting treatment for blood pressure, ask your doctor if you are taking an alpha-blocker. Medications for other conditions, such as fluoxetine (Prozac) and muscle-relaxant drugs, can also promote urine leakage.

Reasons for overactive bladder. The sudden need to pass urine desperately, and maybe not being able to reach the toilet in time, is a slightly different sort of incontinence called overactive bladder. The cause is misbehaviour of the bladder muscle; it starts to contract when it should be stretching to hold more urine. This is called an overactive or irritable bladder (the medical term is detrusor instability, because the bladder muscle is called the detrusor muscle). It means that people with urge incontinence have to pass urine often (probably more than eight times a day and also during the night), but may not pass much each time. Women with urge incontinence often have leakage of urine during sex leakage of urine during sex, usually at orgasm.

Reasons for mixed incontinence. Some people with incontinence have both stress incontinence and an overactive bladder. The ‘stress’ symptoms may be more prominent than the ‘urge’ symptoms, or vice versa.

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