TUESDAY, March 10, 2015 (HealthDay News) -- There's yet another study looking at the potential dangers of hormone replacement therapy for menopausal symptoms, and this one supports the notion that the treatment may not help women's hearts.
The research, a review of collected data on the issue, found that hormone replacement therapy (HRT) does not protect most postmenopausal women against heart disease and may even increase their risk of stroke.
Also, the findings suggest that the harms and benefits of hormone therapy may vary depending on woman's age when she started the therapy, explained study lead author Dr. Henry Boardman, of the cardiovascular medicine department at the University of Oxford in England.
"This 'Timing Hypothesis' may be the critical key to the use of HRT," agreed one expert, Dr. Suzanne Steinbaum, director of women and heart disease at Lenox Hill Hospital in New York City.
"For certain women who fit the criteria, being on HRT early in menopause may be beneficial, and the fear of taking it may be unfounded," said Steinbaum, who was not involved in the new study.
The findings were published March 10 in the journal Cochrane Library.
A woman's natural supply of estrogen diminishes after menopause, and HRT has been widely used to control menopausal symptoms. HRT has also been used to help prevent heart disease in postmenopausal women, the researchers noted.
However, results from the Women's Health Initiative study released in 2002 found that long-term use of HRT boosted a woman's odds for breast cancer as well as strokes. Those findings caused a steep drop-off in the number of women using HRT.
In the new study, Boardman and colleagues analyzed data from a variety of studies involving more than 40,000 women worldwide. The women used HRT for periods between seven months to over 10 years.
Overall, the results showed no evidence that the therapy reduces the risk of death from any cause, death from heart disease, or nonfatal heart attack or angina in healthy women or those with heart disease.
In fact, hormone therapy was associated with a slightly increased risk of stroke, the researchers found.
Timing seemed to matter, however. There was some evidence that women who began hormone treatment within the first 10 years of menopause appeared to have a small amount of protection against death and heart attack, and no increased risk of stroke. However, these women did appear to have an increased risk of blood clots.
"The evidence we have provides some support for the so-called 'timing hypothesis,' but we should bear in mind the size of this effect," Boardman said in a journal news release.
"When we looked at the results according to the age of women, or by how long since their menopause that they started treatment, we found that if 1,000 women under 60 years old started hormone therapy we would expect six fewer deaths, eight fewer cases of heart disease and five extra blood clots over about seven years, compared to a 1,000 similar women who did not start hormone therapy," Boardman added.
So the study findings "need to be carefully considered," he said. "This is a complicated health issue, where the same treatment offers benefits in some women, but harms in others."
Steinbaum agreed that women may need to make the decision to take HRT on a case-by-case basis, in consultation with their physician.
"Hormone replacement therapy for postmenopausal women has been controversial," she said. "This new study published in the Cochrane Library, looking at over 40,000 women, added to the confusion, but also helped to establish potential guidelines."
Dr. Taraneh Shirazian is an assistant professor of obstetrics, gynecology and reproductive sciences at the Icahn School of Medicine at Mount Sinai, in New York City. She said that, as of now, HRT "use is recommended for the shortest period of time for symptom control due to the risks of blood clots, stroke and slight increase in breast and ovarian cancer risk."
"This study suggests that if used further from menopause, the cardiac benefit is not obtained and that the risks of blood clots and stroke increase," Shirazian added. "It is important to consider starting age of HRT, other medical conditions, and family history of breast/ovary when considering the use of HRT in individual women."
The American Academy of Family Physicians has more about hormone replacement therapy.