HRT for postmenopausal women has been the subject of discussion and speculation since the 1960s. At first, HRT was thought to be mainly beneficial because it reduced cases of cardiovascular disease, osteoporosis and colon cancer. It was considered that these benefits outweighed the negative side effects of an increased risk of breast cancer and blood clots.
However, in 2002, results from the Women's Health Initiative (WHI) in the US found that HRT did not offer protection against cardiovascular disease.
These conflicting results led to what is known as the 'timing hypothesis'. The question was asked whether hormones from HRT might be safer and more beneficial if they are replaced as they naturally start to drop off, around the time of menopause, rather than introducing them later in life.
Researchers in Denmark have published the results of a trial into women given HRT early after the menopause. They randomly split 1,006 healthy women aged 45 to 58 into two groups: the first group got HRT; the second group got no treatment.
All the women in the study were near menopause and no more than two years away from their last menstrual period.
The trial was begun in the early 1990s and was designed to run for 20 years. However, researchers stopped it early - after about 10 years - once the results from the WHI and another trial emerged which reported that using HRT might result in more harm than benefit in postmenopausal women.
As a result, the women involved in the trial were advised to stop treatment.
However, the researchers continued to check on the women enrolled on the study for a further six years.
In contrast to what happened in the WHI, the Danish women who took HRT were less likely to die over the course of the study or be hospitalised because of a heart attack or heart failure. After the 10 year period, 16 women who had received HRT either died, were admitted to hospital with heart failure or had a heart attack. That compared with 33 women who had been placed in the control group and had not received HRT.
The researchers also found that there were no meaningful differences in strokes, dangerous blood clots or cancers between the two groups.
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