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Aspirin reduces the risk of asthma by 10% in women reported two newspapers (13 March 2008). The newspaper reports of a well-conducted trial of 37,270 women with no history of asthma were generally accurate. The study's results appear reliable, but may not apply to all women.

On 13 March 2008 two newspapers (1, 2) reported that aspirin could cut the risk of asthma in women by 10%.
The reports were based on a well-conducted randomised controlled trial (3) published in Thorax, involving 37,270 female health professionals who took either 100 mg of aspirin on alternate days or a placebo. Questionnaires were completed by the women over a ten-year follow-up period, which included a question relating to newly diagnosed asthma. The results showed a 10% reduction in the risk of newly diagnosed asthma with aspirin use. The results are likely to be reliable, however, they may not apply to all women.
The newspapers briefly, but accurately, reported the main result of the study.

Evaluation of the evidence base for the risk of adult-onset asthma associated with aspirin use in otherwise healthy women

Where does the evidence come from?

The study was led by Dr T. Kurth from the Division of Preventative Medicine, Brigham and Women's Hospital, Boston who collaborated with researchers from a number of epidemiological research centres and medical schools. The study was funded by the National Heart, Lung and Blood Institute and the National Cancer Institute, USA.

What were the authors' objectives?

To determine the change in risk in adult-onset asthma in otherwise healthy women that is associated with regular low-dose aspirin use.

What was the nature of the evidence?

This was a double blind, randomised controlled trial (RCT) involving 37,270 female health professionals of at least 45 years of age, who were not already taking aspirin or non-steroidal anti-inflammatory drugs more than once a week, anticoagulants or corticosteroids, and who had no history of asthma, coronary heart disease, cancer, or other chronic illness. The diagnosis of asthma was self-reported by the women during health questionnaires completed twice in the first year, and then yearly over the approximately ten year follow-up period. Other information obtained in this way related to compliance, side effects, other newly developed diseases, dates of diagnoses, and personal characteristics and habits.

What interventions were examined in the research?

The women were randomised to receive either 100 mg of aspirin on alternate days (19,934 women) or placebo (19,942 women).

What were the findings?

During the follow-up period, 1835 women reported newly diagnosed asthma; 872 receiving aspirin and 963 receiving placebo; a significant 10% reduction in the risk of adult-onset asthma in women taking aspirin. This reduction was not related to age, smoking status, exercise regime, hormonal treatments, or vitamin E intake, however, aspirin did seem more beneficial in women with lower body mass index compared to women with a BMI of 30kg/m2 or over.

What were the authors' conclusions?

The administration of 100 mg of aspirin on alternate days reduced the risk of newly reported diagnosis of asthma.

How reliable are the conclusions?

This was a well-conducted RCT, involving a large number of women, over a prolonged period of follow-up. The study relied upon the self-reporting of diagnoses, rather than the examination of medical records. However, the question relating to asthma diagnosis was collected alongside a range of other information, with no indication to the respondent that this was a primary outcome of the study. Strict inclusion criteria were applied, and therefore, although the results are likely to be reliable, they may not be generalisable to all women.

Systematic reviews

Information staff at CRD searched for systematic reviews relevant to this topic. Systematic reviews are valuable sources of evidence as they locate, appraise and synthesize all available evidence on a particular topic.

There were no related systematic reviews identified on the Cochrane Database of Systematic Reviews (CDSR), however there was one on the Database of Abstracts of Reviews of Effects (DARE)(4).

References and resources

1. Aspirin can cut risk of asthma in women by 10pc. Daily Telegraph, 13 March 2008, p10.

2. How aspirin could help fight asthma for women. Daily Mail, 13 March 2008, p31.

3. Kurth T, Barr RG, Gaziano JM, Buring JE. Randomised aspirin assignment and risk of adult-onset asthma in the Women's Health Study. Thorax Published Online First: 13 March 2008. doi:10.1136/thx.2007.091447.

4. Jenkins C, Costello J, Hodge L. Systematic review of prevalence of aspirin induced asthma and its implications for clinical practice. BMJ 2004;328:434. [DARE Abstract]