Estrogen-only hormone replacement therapy (HRT) raises the risk of asthma in menopausal women, a recent study has cautioned.
Compared with women who had never used any form of HRT, those who did use it were 21pct more likely to develop asthma.
Almost one in 10 women with a natural menopause (9.4pct), and more than one in four (28pct) of those with a surgically induced menopause, used HRT containing oestrogen alone.
The risk of asthma was significant only among those using oestrogen alone.
Among these women the overall risk of asthma was 54pct higher than among those who had never used any form of HRT.
Oestrogen only users who had never smoked and those who had had some form of allergy before their asthma diagnosis were at greatest risk of developing asthma- 80pct and 86pct higher, respectively.
A small increased risk for asthma was also seen in women using combined oestrogen and progesterone HRT who were either non-smokers or who had had some form of allergic reaction in the past.
They researchers said that while their findings point to an increased risk of asthma, this must be judged in "the light of all the other health effects of HRT use, including its beneficial effect on the quality of life of menopausal women."
The study appears in journal Thorax.