The new research stands in contrast to the common recommendation that women with leaky bladders stay away from caffeinated foods and beverages.

"If a woman feels she wants to abstain from caffeine that's completely fine, but based on our results, women with moderate incontinence shouldn't be concerned," said Mary Townsend, the study's lead author from Brigham and Women's Hospital and Harvard Medical School in Boston.

Still, the findings cannot say whether caffeine might have a shorter-term impact by making women need to urinate soon after eating or drinking something caffeinated.

According to Townsend, there are some biological reasons for women with incontinence to stay away from caffeine -- such as that it increases the production of urine and may give some the urge to go.

But it's been unclear whether a daily caffeine habit is tied to worsening incontinence over the long run.

To try to answer that question, the researchers looked at data on about 21,500 women enrolled in two large studies, each of which tracked the long-term health of U.S. nurses through surveys starting in the 1970s or 1980s.

Townsend and her colleagues selected women with moderate incontinence -- defined as leaking urine one to three times per month -- from participants who were asked about incontinence and caffeine consumption in 2002 or 2003.

The women were questioned about how much caffeine they ate or drank in the form of coffee, tea, soda or chocolate over the previous few years.

Two years later, when they were again surveyed about incontinence, about 20 percent of women said their symptoms had gotten worse and they now leaked urine at least once per week. That was consistent regardless of how much caffeine they'd reported eating and drinking.

The researchers also didn't find a link between women who increased their caffeine consumption between the survey years and worsening urinary symptoms -- either for general incontinence or for overactive bladder in particular. Women can also suffer from stress and overflow incontinence, said Dr. Larissa Rodriguez, co-director of the division of female urology, reconstructive surgery and urodynamics at the David Geffen School of Medicine at the University of California, Los Angeles, in an email.

Leaks related to stress incontinence can be brought on by any activity that puts stress on the bladder, like sneezing or laughing. Overflow incontinence occurs when the bladder does not empty properly, and urge incontinence or overactive bladder is the sudden need to go the bathroom.

As for treatments, behavioral changes, weight loss and certain exercises may help, said Rodriguez, who wasn't involved in the new study.

"There are not many effective medications but minimally invasive surgeries can be curative," she added.

According to the National Institutes of Health, which funded the study, the majority of women can get relief without surgery.

Townsend said most women in the study did not even tell their doctors about their incontinence.

She also said the new findings, published in Obstetrics & Gynecology, need to be confirmed with more research because there's a possibility that caffeine could make urinary symptoms worse over longer than a few years.

The study was also limited because incontinence symptoms were reported by the women themselves and not measured by a doctor, and the researchers didn't take treatment for incontinence into consideration.

SOURCE: bit.ly/IJ1RzF Obstetrics & Gynecology, online April 23, 2012.

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