Adult onset asthma is often progressive1 and the cause of considerable morbidity. Some asthma developing de novo in adults can be attributed to environmental factors, such as occupational sensitisers. When such an association is recognised, asthma can often be prevented, so searching for aetiological factors is well worthwhile. Hormone replacement therapy (HRT) may be one such factor.

Postmenopausal HRT was used widely until recently, being seen as the way for women not only to appear more youthful and glamorous following the menopause but also to be healthier. Various observational studies had suggested a reduced risk of diseases such as osteoporosis, heart disease and possibly dementia. However, when the results of prospective studies became available the picture was, alas, rather less positive. Not only did these studies fail to confirm many of the alleged benefits of HRT, they suggested or confirmed important adverse effects including an increased risk of breast cancer, ovarian cancer, venous thrombo-embolism, heart disease, cognitive decline and, more recently, mortality from lung cancer.2–8 Should late-onset asthma be on this list?

Cross-sectional studies have shown an association between the use of HRT and a diagnosis of asthma and asthma symptoms.9–11 The studies have varied in design and in how asthma was diagnosed, but the findings have been fairly consistent in showing a modest association between HRT use and reported asthma, with ORs ranging from 1.38 to 1.57.9–11 The associations with symptoms and asthma medication were of similar magnitude.9–11 Two studies found the strongest association in never smokers9 11 and two showed an interaction with body mass index (BMI), in that the effects of HRT were seen largely in women with a low BMI.9 10 Having a high BMI per se was associated …