Swedish researchers, writing in The British Medical Journal, say that HRT - an oestrogen treatment - can prevent bone fracturing, but its beneficial effect wears off within five years of coming off it.

For every year it is taken, the chance of weakening bone structure decreases. In the study of over 1,000 women, those who took HRT for more than five years were at least 70% less likely to suffer bone fractures than women who had never taken it.

Breast cancer

However, other research shows that, the longer women take HRT, the more likely they are to develop other diseases, such as breast cancer.

The researchers found that HRT was more effective in protecting bones when combined with the hormone, progestin. Low doses of HRT did not have much effect.

The scientists from the Swedish Hip Fracture Study Group discovered that it makes no difference if the women taken the therapy before or after the menopause.

Anti-ageing pill

Another article in the BMJ says the long-term use of HRT should only be targeted at women who have a high risk of developing brittle bones and a low risk of developing breast cancer.

Kay-Tee Khaw, professor of clinical gerentology, says: "The idea of an anti-ageing pill in the form of oestrogen therapy is certainly attractive, but it is unlikely to be the solution to healthy ageing in women.