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Their study, published in the European Heart Journal, suggests it is not hormone replacement therapy that raises the risk of heart attacks in women, but the way it is taken.
It also shows that a large study called the Women's Health Initiative, which frightened many women away from HRT after it was stopped in 2002, may not be the last word on treatment.
"This study is the first, big observational study that addresses the influence of various regimens, doses and routes of administration," Dr Ellen Lokkegaard of the Rigshospitalet in Copenhagen, who led the study, said.
How the research was done
The Women's Health Initiative was stopped in early 2002 because HRT combining oestrogen and progestin appeared to cause a 24% higher risk of breast cancer. Women taking the combination of hormones had twice the normal rate of blood clots, and higher risks of stroke and heart attack.
Most of the women took Premarin or Prempro, made by Wyeth. Sales of all HRT drugs plummeted. But some experts suggested the study gave a very limited picture of HRT and said perhaps different drugs, taken by women at younger ages, might have other effects.
Lokkegaard's team studied 698 000 women aged 51 to 69 in Denmark, who take part in a national health database.
"Overall, we found no increased risk of MI (heart attack) with the current hormone therapy compared with women who never used hormone therapy," they wrote in their report. Younger women aged 51 to 54 had a 24% higher risk of heart attack than women who had never taken HRT - but the risk in this age group is low to start with.
What the findings showed
Women who took continuous HRT - when oestrogen and progesterone are taken together every day - had a 35% higher risk of heart attack compared with women who had never used HRT. This is the way Prempro was dosed.
But if HRT was taken on a cyclical basis - with oestrogen pills for 25 days, adding progestin for the second half of the month and then taking no pills for three to five days - women had a lower risk of heart attack. Patches or gels lowered the risk of heart attack by between 38% to 44%.
The type or dose of oestrogen or progesterone did not matter, they found. Women are currently advised to take the lowest dose of HRT possible for the shortest possible time.
"Our study does not change indications and duration recommendations for HRT," Lokkegaard said. "But the main message is that when hormone therapy is indicated for a woman, then a cyclic combined regimen should be preferred, and that application via the skin or the vagina is associated with a decreased risk" of heart attack.
She said she believed HRT taken this way also lowers the risk of breast cancer, blood clots and stroke. – (Reuters Health, October 2008)
Read more:
New study says HRT may be safe
