The knot, or sphincter, opens and closes as needed to let urine out. When you urinate, the bladder contracts, and the sphincter opens. Stress incontinence, another type of bladder control problem, involves a weakening of the sphincter. Bladder instability often leads to the need to run for the bathroom, or to embarrassing accidents when urine leaks out without warning. In an article published in the journal Obstetrics and Gynecology, Lily A. Arya, MD, and colleagues from Brown University School of Medicine in Providence say drinking several cups of coffee, tea, or cola a day could increase the risk of bladder instability in women who already have bladder-control problems.
Age also increases the risk of bladder instability.
In the study, those who were found to have bladder instability tended to be in their mid-50s, about 10 years older than those without the instability. The researchers also found that the women with bladder instability were more likely to be smokers. Arya and colleagues say the link between caffeine and detrusor instability may have several explanations, including the possibility that caffeine stimulates the muscles of the bladder, causing them to contract involuntarily. But there may actually be a simpler explanation, says Blaivas, a professor of urology at Weill Medical College of Cornell University and attending surgeon at New York Hospital Cornell Medical Center and Lenox Hill Hospital in New York. So women who drink lots of caffeine-containing drinks make more urine, and use their bladders more, than other women.