Postmenopausal women who take estrogen for years are more likely to experience incontinence than those on the hormone for a shorter time or not at all, a new study finds.

Of 167 women surveyed in the early 1990s and again in 2004, those who had taken estrogen for five years or more were three to four times more likely to report bladder control problems in the second survey than women who had not taken estrogen or took it for less than five years.

“Looking at a patient’s history of estrogen use may be an important factor in (gauging) their risk for developing urinary incontinence,” said Dr. Gina Northington, an author of the study who specializes in urogynecology at Emory University in Atlanta.

Some women take estrogen after menopause to help with symptoms such as hot flashes and vaginal dryness.

For the study, published in the journal Menopause, 167 postmenopausal women filled out questionnaires in 1993, stating whether they had never used estrogen, used estrogen for less than five years, or used it for five or more years.

Eleven years later, of the 167 women who said they didn’t have incontinence problems in the first survey, 47 reported having a new case of urinary incontinence.

And more than 31 of those women said their incontinence made it difficult to perform daily tasks such as shopping, attending social events, visiting friends and exercising.

Of the 47 women with new bladder control problems, seven had used estrogen for more than five years. That compares with just seven of 120 women without incontinence who had used estrogen for that long.

Northington pointed out the study had a few weaknesses. “We only asked women if they took hormones containing estrogen,” she told Reuters Health. “We didn’t measure the level of estrogen and we didn’t ask about progesterone.”

The reason why estrogen therapy would affect bladder function is still not well understood.

“Some studies have suggested hormones such as estrogen may influence nerves that control the bladder,” said Dr. Leslie Rickey, a gynecologist who specializes in bladder problems at the University of Maryland Medical Center.

“Urinary problems increase with age,” said Rickey, who was not part of the study. “We’re not sure if it’s due to the aging process or estrogen levels or the combination of the two.”

Up to half of women 45 years and over have reported experiencing incontinence at least once in their lifetime, according to a menopause study of nearly 2,800 women that was funded by the National Institutes of Health.

Rickey does find large studies helpful in spotting patterns in the relationship between bladder function and estrogen, but it’s difficult to apply the data to an individual patient.

“It’s still not known which individual women on estrogen therapy are at risk for developing bladder control problems,” she told Reuters Health.

Northington doesn’t recommend stopping estrogen but she does urge women to talk with their doctor before starting therapy.

“In addition to other risks associated with estrogen such as breast cancer and blood clots, this is another reason to make sure estrogen is taken for the shortest amount of time, if it needs to be taken,” said Northington.

SOURCE: Menopause, October 7, 2011.