Overview

In people with an overactive bladder (OAB), the layered, smooth muscle that surrounds the bladder (detrusor muscle) contracts spastically, sometimes without a known cause, which results in sustained, high bladder pressure and the urgent need to urinate (called urgency).Normally, the detrusor muscle contracts and relaxes in response to the volume of urine in the bladder and the initiation of urination.

People with OAB often experience urgency at inconvenient and unpredictable times and sometimes lose control before reaching a toilet. Thus, overactive bladder interferes with work, daily routine, intimacy and sexual function; causes embarrassment; and can diminish self-esteem and quality of life.

Urination

Urination (micturition) involves processes within the urinary tract and the brain. The slight need to urinate is sensed when urine volume reaches about one-half of the bladder's capacity. The brain suppresses this need until a person initiates urination.

Once urination has been initiated, the nervous system signals the detrusor muscle to contract into a funnel shape and expel urine. Pressure in the bladder increases and the detrusor muscle remains contracted until the bladder empties. Once empty, pressure falls and the bladder relaxes and resumes its normal shape.

Incidence and Prevalence

Overactive bladder affects men and women equally. The U.S. Department of Health and Human Services has reported that approximately 13 million people in the United States suffer from OAB and other forms of incontinence.