Health risks related to hormone therapy with oestrogen might go away after women stop the treatments, a new study suggests.
The results are good news for women in their 50s, said Graham Colditz, a professor at the Washington University School of Medicine, because that's the age group most likely to take hormones to treat menopause symptoms.
"But that doesn't mean continuing to take them for five to 10 years won't have some risks emerge," Colditz, who wrote an editorial that was published along with the study, told.
The new research focused on some of the same women who participated in a study that first raised concerns about the safety of hormone therapy. The women all had undergone hysterectomy before joining the study; after joining, they were assigned to a group that received oestrogen pills.
Findings from the federally-funded study, called the Women's Health Initiative, showed in 2002 that a combination of hormones including oestrogen was tied to more strokes and blood clots, and fewer hip fractures.
But now, several years after the women stopped taking the oestrogen, their risks for complications - including not just strokes and blood clots but breast cancer and heart problems - have returned to normal, according to a report in the Journal of the American Medical Association.
The results apply only to women in their 50s, and only to those taking oestrogen after a hysterectomy; for older women taking a combination of hormones, the risks tied therapy persist.
Hysterectomy - removal of the uterus - is the second most common surgery among women, and one third of women have had a hysterectomy by age 60. Oestrogen by itself can lead to cancer of the lining of the uterus; that's why women who have a uterus and need hormone therapy must take a combination instead of oestrogen alone.
The original findings from the Women' Health Initiative contributed to ending the practise of prescribing hormone therapy to women for preventing heart disease, said Colditz.
But many women who have had a hysterectomy use oestrogen to relieve the symptoms of menopause, "although questions remain regarding the safety of this treatment," Colditz wrote.
The new study
The new study followed 7,645 women for 10 years - six years during hormone treatment and four years after ending the treatment.
Women randomly assigned to take hormone therapy used Premarin, a hormone therapy made by Wyeth, a pharmaceutical company now owned by Pfizer.
During the treatment, stroke was 36% more likely and blood clots were 47% more likely among women who took oestrogen compared to those who didn't.
That meant 45 out of every 10,000 women taking hormone therapy had a stroke compared to 34 out of every 10,000 women who didn't take oestrogen.
And 23 of every 10,000 women taking oestrogen had a blood clot compared to 15 out of every 10,000 women who were not on the treatment.
Fewer heart attacks and deaths
However, after 10 years, there was no significant difference between the groups for these conditions.
For women in their 50s, oestrogen treatment even appeared to have some benefits over time. The hormones were linked to a 46% drop in the risk of a heart attack and a 27% drop in the risk of dying after 10 years.
That translated to 12 fewer heart attacks and 13 fewer deaths for every 10,000 women in this age group.
For women in their 70s, however, those benefits were missing, and for some conditions their risks were increased if they took oestrogen.
The authors wrote that oestrogen therapy was tied to 16 extra heart attacks and 19 additional deaths among women in this older age group at the end of the 10 years.
"If you're a woman in your 70s, there's very little reason to initiate oestrogen," Dr Andrea LaCroix, of the Fred Hutchinson Cancer Research Centre in Seattle and the lead author of the study, said.
Risk of breast cancer with HRT
Though the risk of breast cancer in this study appeared to be the same between women who took oestrogen and those who didn't, Colditz said other studies have found a link between the cancer and the hormone therapy.
A different arm of the Women's Health Initiative - which ended in 2002 - found an increased risk of breast cancer and heart disease among women who took oestrogen plus progesterone hormone therapy.
Colditz added that it's not clear what the age limit or length of time on oestrogen therapy should be to provide the most benefit and the least risk.
The women in this study adhered to the oestrogen regimen for an average of three and a half years, and continued to take the hormone at some level for a total of six.
"Some women are long term hormone therapy users and they don't want to stop," LaCroix said. "Our data don't speak clearly for them." (Reuters Health/ March 2011)