Hot topic - Oestrogen-only HRT and stroke risk
3 March 2004 - written by Bupa's Health Information Team
What has happened?
An american study looking at the effect of oestrogen-only HRT on 11,000 women aged 50-79 years has been stopped a year early.
The study was designed to investigate whether or not the use of oestrogen-only HRT reduced the risk of developing heart disease. In the study, women were either given a daily dose of 0.625mg oestrogen or a placebo. The study was scheduled to run for eight years, but was stopped after seven.
Why was the study stopped?
The researchers discovered that the use of oestrogen-only HRT did not reduce the risk of developing heart disease, but it did increase the risk of developing a stroke. Since the study had been running for seven out of its eight years, the researchers believed that the results were unlikely to change during the final year and decided to end the study one year early.
What did the results show?
The researchers found that oestrogen-only HRT did not reduce the risk of developing heart disease.
However, the use of oestrogen-only HRT did increase the risk of developing a stroke by roughly the same amount as the use of combined oestrogen-progesterone HRT. This is equivalent to an extra 8 women developing a stroke per 10,000 women a year. In other words, the risk of developing a stroke increased from 21 in 10,000 women to 29 in 10,000 women.
In addition, the researchers believe that the data will also show that the use of oestrogen-only HRT by women over the age of 65 years may increase the risk of developing dementia.
On a positive note, the researchers did not find that the use of oestrogen-only HRT increased the risk of breast cancer (unlike the combined oestrogen-progesterone type of HRT which does increase the risk slightly).
What type of HRT was involved?
The type of HRT used in this study was the oestrogen-only form of HRT. This type of HRT is only used in the UK by women who have undergone a hysterectomy. Roughly 60-70,000 hysterectomies are performed in Britain each year.
All other women using HRT receive the combined oestrogen-progesterone type of HRT.
What does this mean?
Oestrogen-only HRT does have a number of benefits:
- oestrogen-only HRT is effective in the relief of the short-term symptoms of the menopause, for example hot flushes and night sweats
- oestrogen-only HRT is also effective in reducing the risk of developing osteoporosis
However, due to the lack of effect in reducing heart disease risks and the increased risk of stroke, and possibly dementia, the US Food and Drug Administration (FDA) advises that:
"Postmenopausal women who use or are considering using estrogen or estrogen with progestin discuss the therapy's benefits and risks with their physicians. These products are approved therapies for relief from moderate to severe hot flashes and symptoms of vulvar and vaginal atrophy. Although hormone therapy is effective for the prevention of postmenopausal osteoporosis, it should only be considered for women at significant risk of osteoporosis who cannot take non-estrogen medications. The FDA recommends that estrogens and progestins should be used at the lowest doses for the shortest duration needed to achieve treatment goals."
What is the current HRT advice?
The UK Department of Health has said that it will bear these latest findings in mind and will update its advice when necessary.
In the UK, the most up-to-date advice has been issued by the Committee on the Safety of Medicines (CSM) in December 2003. At this time the CSM issued new advice to doctors concerning the use of combined oestrogen and progesterone HRT medications.
The full advice can be read in our Hot Topic - Long-term HRT use, osteoporosis prevention and cancer risk.
In summary, the advice was that HRT should only be used for the short-term relief of menopausal symptoms and for the prevention of osteoporosis in women who were unable to take other osteoporosis prevention treatments. In both instances, the CSM advises that HRT is used for the minimum length of time and at the lowest effective dose possible.
The CSM also advises that both the woman and her doctor should review the use of HRT at least once a year.
For women who have experienced premature menopause (before the age of 50 years), due to ovarian failure or hysterectomy, the CSM advises that HRT may be used to treat their menopausal symptoms and prevent osteoporosis until the age of 50 years. After this age, the CSM says that therapy for prevention of osteoporosis should be reviewed and HRT considered as an option after other osteoporosis prevention treatments have been explored.
Further information
Bupa resources:
- Bupa factsheet: Strokes
- Bupa Key facts: HRT and breast cancer risk
- Bupa factsheet: Osteoporosis
- Bupa factsheet: The menopause and HRT (hormone replacement therapy)
- Bupa factsheet: Breast awareness and screening
- Bupa factsheet: Breast cancer
- Bupa factsheet: Breast lumps
External website:
- National Institutes of Health questions and answers about the oestrogen-alone study
- Medicines and Healthcare products Regulatory Agency HRT information
