Women on oestrogen-only HRT ‘at increased risk of asthma’
09 February 2010

Women who use a particular type of hormone replacement therapy are more likely to develop asthma, according to new research.

A study of 57,664 women found those taking the oestrogen-only form of the treatment were 54% more at risk of getting asthma than those who had never used any HRT.

Women were quizzed about their use of HRT and development of asthma symptoms every two years between 1990 and 2002. None of these women had asthma when menopausal symptoms began, for which HRT is offered as relief.

During the period 569 women were newly diagnosed with asthma, corresponding to a rate of 1.15 cases per 1,000 women a year.

Compared with women who had never used any form of HRT, those who did use it were 21% more likely to develop asthma, after adjusting for factors likely to influence the results, although the researchers said this was not statistically significant.

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.

Dr Françoise Clavel-Chapelon, of the National Institute of Health and Medical Research in Paris, said: ‘Postmenopausal use of oestrogen alone was associated with an increased rate of newly diagnosed asthma in menopausal women.

‘The major increase in asthma prevalence observed in most developed countries in recent years suggests it may in part be due to environmental factors.

‘Differences in asthma incidence during the life cycle suggest that reproductive hormones influence the development of asthma and asthma severity.’

Leanne Metcalf, Director of Research at Asthma UK, said: ‘There is now a large body of evidence suggesting a link between female hormones, including the use of HRT, the development of asthma and its severity. However this is the first large-scale and long-term study to suggest that it is oestrogen-only HRT which significantly increases the risk.

‘It’s still too early to say exactly how the menopause or taking HRT affects asthma symptoms and who is likely to be affected. Therefore women who are intending to use HRT need to weigh up the broader health benefits of HRT with the possibility of an increased risk of asthma, especially those with a history of asthma or allergy in their family.

‘We know that some women develop asthma symptoms during periods of hormonal change so it’s important to speak to a doctor if you start to experience regular symptoms like breathlessness, cough or wheeze.’

The findings were published in the journal Thorax.