UK research probing the effect of HRT on health has been halted after an earlier trial linked it to a tiny increase in heart disease.

The Medical Research Council (MRC) said that running the project for the next 14 years would be a waste of time as other researchers in the US had already come up with the answers it was seeking.

It said that women in the trial had not been put at risk.

We have no concerns about the safety of women involved in the study

Dr Philip Hannaford, Aberdeen University

A British expert says that there is now enough evidence to suggest that women taking certain combinations of HRT hormones on a long-term basis should consult their doctors about alternative HRT formulations.

However, there is currently no evidence that any other formulation is safer in the long term.

The idea behind the WISDOM trial was to recruit more than 16,000 women aged between 50 and 69 and follow their health over the next decade to see how much difference HRT made to it.

Surprising find

It had been expected that HRT might actually decrease their risk of heart disease over the long-term.

This is because it contains hormones which, before the menopause, protect women from heart disease.

However, in July, a very similar trial which had started earlier in the US was halted early after doctors were surprised by a very slight increase in heart disease cases among thousands of women taking HRT.

This small rise in risk amounted to eight extra cases for every 10,000 women taking the hormones.

There was no overall increase in death rates for women taking the HRT.

However, the strong likelihood that no heart benefits would emerge at the end of the trial - and perhaps that women might even face a tiny increased risk - meant that organisers felt it was unethical to continue.

The particular combination of drugs used in the US trial is not marketed in the UK, although a similar combination, called Premique, accounts for approximately 9% of the several million women estimated to be taking HRT.

Women have been advised not to stop taking their medication without talking to their GPs - who may be able to offer an alternative.

In July, the UK's Chief Medical Officer said that on current evidence, every type of HRT should be considered the same in terms of safety.

'No risk'

The MRC, after investigating the results, called off their own trial on Wednesday, but stressed that none of the more than 5,000 women recruited so far were at risk.

Professor Ray Fitzpatrick, who chaired their investigation, said: "When our trial began recruiting in 1999, there were important questions about the risks and benefits of HRT long term that needed to be answered.

Women should visit their doctor, who may well be able to suggest an alternative form of HRT

Dr John Stevenson, Women's Health Concern

"But since then new findings have provided evidence in relation to those questions."

He said there was already strong evidence that taking HRT long term increased the risks of breast cancer, although it offered protection against brittle bone disease.

"However, there is no trial evidence that HRT protects women from cardiovascular disease and it may even increase their risk in the long term."

'Answers needed'

Dr John Stevenson, chairman of Women's Health Concern and an expert in HRT from the Royal Brompton Hospital in London, told BBC News Online that it was regrettable that the study had ended.

He said that a large proportion of the women in the US study were overweight, and that this might have influenced the overall result.

"I would have liked to have seen results from the WISDOM trial which I feel could have had a different outcome with regard to heart disease. It's a shame it had to end early."

However, he said that there was now enough evidence that this and similar combinations should not be taken long-term.

He said: "Women should visit their doctor, who may well be able to suggest an alternative form of HRT.

"However, what we badly need are long-term safety studies about all forms of HRT."

However, another investigator, Professor Philip Hannaford, from the University of Aberdeen, said: "We have no concerns about the safety of women involved in the study.

"Women taking HRT or involved in the WISDOM study should seek advice from their family doctors before making decisions about changing their current medication."