"This study presents some underlying mechanisms for the beneficial effect of
[topical oestrogen formulations] after menopause and supports the application of
oestrogen in postmenopausal women suffering from recurrent UTIs," wrote the
study's authors, from the Karolinska Institute in Stockholm, Sweden.
About half of all women will experience at least one urinary tract infection
in their lifetime, according to the study. For about 25% of these women, the
infection will come back again within six months.
Low oestrogen levels have previously been linked to recurrent infections, and
the new study sought to identify exactly how oestrogen might affect a woman's
risk of recurrent urinary tract infections.
For the study, the researchers used human cells from postmenopausal women who
had used supplemental vaginal oestrogen for two weeks. They also worked with
mice that were given bacteria that would cause urinary tract infections like
those in humans.
They found that oestrogen encourages production of natural antimicrobial
substances in the bladder. The hormone also makes the urinary tract tissue
stronger by closing the gaps between cells that line the bladder. By gluing
these gaps together, oestrogen makes it harder for bacteria to penetrate the
deeper layers of the bladder wall, the study authors said.
Oestrogen also helps prevent too many cells from shedding from the top layers
of the bladder wall.
"Normally, there's an innate response to infection and some cells die ? sort
of taking one for the team ? and then these cells shed," Hannan said. "But
shedding too much could allow bacteria to get into the deeper tissue, so this
exfoliation is a double-edged sword."
According to the study, oestrogen promotes the redistribution of cells and
prevents excessive loss of cells during an infection.
One expert welcomed the findings.
"This study gives us more information about what we always had a sense was
true: that women do get more [urinary tract infections] after menopause," said
Dr Jennifer Wu, an obstetrician and gynaecologist at Lenox Hill Hospital in New
Although taking oestrogen in pill form is associated with an increased risk
of breast cancer and cardiovascular disease, topical oestrogen is much safer, Wu
said. Topical oestrogen formulations include creams, gels and vaginal
"Only about 1% of oestrogen cream or other topical delivery gets into the
rest of the body's systems," she said.
Although commonplace, women shouldn't accept recurrent urinary tract
infections as a normal part of ageing, Wu said. "Talk to a gynaecologist or
urologist to find out what kinds of therapies are available," she said. "There
are treatments besides antibiotics."
To learn more about urinary tract infections, visit WomensHealth.gov.