What causes urinary incontinence?

Stress incontinence	Urge incontinence
Caused by your bladder being under sudden pressure, such as from laughing, sneezing or exercising. Caused by weakening of muscles that support the bladder.	Urine leakage caused by, or occurring soon after, a sudden, intense urge to urinate. Caused by overactive detrusor muscles surrounding the bladder.
Overflow incontinence	Total incontinence
Inability to fully empty your bladder. Most often caused by a blockage but can sometimes be due to a problem with the detrusor muscles.	Leaking caused by the bladder not being able to store urine at all. Most serious type, usually a problem with the bladder from birth.

These are the main four types of incontinence, however, people may experience symptoms of several types. For instance, mixed incontinence is characterised by symptoms of both urge and stress urinary incontinence.

There is also functional incontinence, urine leaks that are caused by an inability to reach the bathroom to urinate rather than a problem with the bladder itself.

The leading cause of urinary incontinence, particularly stress incontinence, is age-related. One meta-analysis found that out of half a million women aged 55 - 106 across the globe, 37% had symptoms of urinary incontinence. The percentage is slightly lower for older men, with research estimating the figure is more like 15%.

37% of older women across the world suffer from incontinence.

It’s very common in older people because there are many conditions associated with ageing that result in urinary incontinence.

Muscle weakness

The most common cause in older people is the natural weakening of the muscles surrounding the bladder.

There are several key muscles at play when it comes to bladder function:

• pelvic floor muscles - support the bowel, rectum, reproductive organs and the bladder, they contract when the bladder fills and relax when you urinate
• urethral sphincter muscles - control the flow of urine from the bladder
• detrusor muscles - surround the bladder, contracting to help push urine out of the bladder and into the urethra

Just like other muscles in your body, these muscles can gradually weaken over time as you get older, leading to stress and or urge incontinence.

Functional incontinence

Functional incontinence, or disability associated urinary incontinence, is common among the elderly.

This is unlike other types of incontinence in that it is not caused by a problem with the bladder itself. Rather, it is a physical or cognitive disability that means you are often unable to make it to the bathroom in time.

People with physical conditions such as Parkinson’s disease or multiple sclerosis may struggle to reach the bathroom. Equally, those with dementia or confusion may recognise the urge to urinate but are unable to locate the bathroom.

Another very common cause of urine leaks is pregnancy and childbirth, with around 66% of pregnant women complaining about incontinence.

A woman’s bladder can reduce by half during pregnancy

During pregnancy, your body changes a lot to accommodate new growth. This has several combined effects that lead to urinary incontinence. One of the main changes is bladder capacity. Your bladder capacity can also get as low as 272ml by the final trimester, when on average a woman's bladder capacity is around 400 - 550ml. Therefore, your bladder capacity almost halves by the time you’re due.

Incontinence during pregnancy is also linked to:

• excess pressure on the bladder from weight gain and foetal growth, causing you to need to pass urine more often
• hormonal changes relax the muscles surrounding the bladder
• weight gain and growing uterus weaken the pelvic floor and urethral muscles, which can cause involuntary leaks

Pregnancy should be an enjoyable time, but incontinence can significantly impact quality of life for many pregnant women. Your doctor may recommend doing pelvic floor exercises (Kegel exercises) throughout your pregnancy to help prevent and reduce urinary incontinence.

The bladder, and the muscles that support it, rely on systems of nerves in order to function. So when there’s an issue with the nervous system, it can mean the bladder doesn’t function properly.

This is what’s known as neurogenic bladder, or neurogenic lower urinary tract dysfunction. It can result in most types of incontinence, as well as a similar condition called overactive bladder (OAB), which incontinence can be a symptom of.

Neurogenic bladder can be caused by several different conditions, but the most prevalent are neurodegenerative disorders like multiple sclerosis, Alzheimer’s or Parkinson’s disease. For instance, one study found that 60% of patients with Parkinson’s experience bladder symptoms, 30% of which experienced incontinence.

Other causes may include:

• spinal cord injury
• stroke
• major pelvic surgery (e.g hysterectomy)
• nerve damage from diabetes

Depending on the cause of the nerve problems, your doctor will decide what the best treatment option is for your symptoms.

Obesity can cause many health complications, however, it has also been linked to urinary incontinence. One study found that over half of obese patients reported experiencing episodes of urinary incontinence.

Like pregnancy, excess weight causes abdominal pressure, which also puts the bladder under excess pressure. It also causes the pelvic floor muscles to weaken, which results in stress incontinence.

Lifestyle changes such as weight loss, a healthier diet and increased exercise will significantly improve incontinence symptoms.

Whilst less common than in women, incontinence can have specific causes that only occur in men.

The leading cause of incontinence and other bladder problems in men is an enlarged prostate gland, a condition known as benign prostatic hyperplasia (BPH). This is a common condition in men, particularly older men, and is believed to be caused by natural hormone changes as you get older.

When the prostate becomes enlarged and inflamed, it places pressure on the bladder and the urethra. As well as incontinence, this can cause other urinary symptoms such as weak urine flow, straining to urinate and a stop-start flow.

Medicines can cause certain side effects, although not everyone experiences them. Urinary incontinence can be a side effect of some medicines, such as:

• ACE inhibitors for high blood pressure (e.g. ramipril) - can decrease muscle tone in the urethral sphincter
• diuretics (e.g. indapamide) - cause incontinence as they work by increasing urine formation by the kidneys
• certain antidepressants - impair the bladder’s ability to contract
• hormone replacement therapy (HRT) - due to fluctuating hormone levels
• sedatives (e.g. benzodiazepine) - causes certain bladder muscles to relax when they’re not supposed to

Whilst we have covered the most common cause, there are many potential causes of urinary incontinence, including:

• infections such as urinary tract infections (UTIs) - they can inflame and irritate the bladder, causing leakage
• kidney diseases
• constipation - places more pressure on the bladder
• too much caffeine or alcohol - both can irritate the bladder
• menopause - muscles and urethra lining weaken due to low oestrogen
• drinking too little or too much fluid

It’s important you get your incontinence diagnosed so you can get the right treatment. Most cases of incontinence can be treated with lifestyle changes, pelvic floor exercises and bladder training as well as incontinence products (e.g. absorbent pads).

For more tricky cases of incontinence, you can use prescription treatment. Medicines such as Detrusitol and Vesicare help to increase bladder control and the amount of urine it can hold, reducing your need to empty your bladder.