Causes

Stress incontinence occurs when the muscles and other tissues that support the urethra (pelvic floor muscles) and the muscles that control the release of urine (urinary sphincter) weaken.

The bladder expands as it fills with urine. Normally, valve-like muscles in the urethra — the short tube that carries urine out of your body — stay closed as the bladder expands, preventing urine leakage until you reach a bathroom. But when those muscles weaken, anything that exerts force on the abdominal and pelvic muscles — sneezing, bending over, lifting or laughing hard, for instance — can put pressure on your bladder and cause urine leakage.

Your pelvic floor muscles and urinary sphincter may lose strength because of:

• Childbirth. In women, tissue or nerve damage during delivery of a child can weaken the pelvic floor muscles or the sphincter. Stress incontinence from this damage may begin soon after delivery or occur years later.
• Prostate surgery. In men, the surgical removal of the prostate gland to treat prostate cancer (prostatectomy) is the most common factor leading to stress incontinence. This procedure can weaken the sphincter, which lies directly below the prostate gland and encircles the urethra.

Contributing factors

Other factors that may worsen stress incontinence include:

• Illnesses that cause chronic coughing
• Obesity
• Smoking, which can cause frequent coughing
• High-impact activities, such as running and jumping, over many years