Overactive bladder (OAB) is a syndrome which affects around 12 per cent of men and women, and incidence increases with age so that by the age of 80 around 70 to 80 per cent of people are affected.1 Patients with OAB present with symptoms of urgency, increased daytime frequency and nocturia.2 Around 33 per cent of people with OAB will exhibit urinary incontinence, which affects women more than men.
Overactive bladder has a significant negative effect on patients' quality of life and can lead to social isolation and depression.1,3 Overactive bladder syndrome with urge incontinence is associated with early institutionalisation, financial cost and increased morbidity and mortality. 4
Lower urinary tract function
The function of the lower urinary tract (LUT) is to store and intermittently release urine, and requires the coordination of smooth and striated muscles in the bladder and bladder neck, urethra and urethral sphincter within the bladder outlet. Coordination between these organs is mediated by a complex neural control system located in the brain, spinal cord and peripheral ganglia.
The average adult bladder can hold between 350ml and 500ml of urine. The sensation of bladder fullness occurs when the bladder is around half full (200ml), but results in no increase of pressure from the detrusor muscle until the bladder's capacity is reached.