Background: Randomised data in men show a small but significant reduction in the risk of adult-onset asthma among those given aspirin. The results from an observational study in women suggest that frequent use of aspirin decreases the risk of adult-onset asthma, but randomised data in women are lacking. A study was undertaken to test the effect of 100 mg aspirin or placebo on alternate days on the risk of adult-onset asthma in the Women’s Health Study.
Methods: A randomised, double-blind, placebo-controlled clinical trial of aspirin and vitamin E was performed in apparently healthy women with no indication or contraindication to aspirin therapy and no history of asthma at study entry. Female health professionals self-reported an asthma diagnosis on yearly questionnaires.
Results: Among 37 270 women with no reported history of asthma prior to randomisation and during 10 years of follow-up, there were 872 new cases diagnosed with asthma in the aspirin group and 963 in the placebo group (hazard ratio 0.90; 95% CI 0.82 to 0.99; p = 0.027). This apparent 10% lower relative risk of incident adult-onset asthma among those assigned to aspirin was significantly modified by body mass index, with no effect in women with a body mass index of ⩾30 kg/m2. The effect of aspirin on adult-onset asthma was not significantly modified by age, smoking status, exercise levels, postmenopausal hormone use or randomised vitamin E assignment.
Conclusions: In this large randomised clinical trial of apparently healthy adult women, administration of 100 mg aspirin on alternate days reduced the relative risk of a newly reported diagnosis of asthma.
Trial registration number: NCT00000479
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Funding: The Women’s Health Study is supported by grants from the National Heart, Lung, and Blood Institute (HL-43851) and the National Cancer Institute (CA-47988). RGB was supported by a Robert Wood Johnson Generalist Physician Faculty Scholar Award.
Competing interests: TK has received investigator-initiated research funding from the National Institutes of Health, Bayer AG, McNeil Consumer & Specialty Pharmaceuticals, and Wyeth Consumer Healthcare; he is a consultant to i3 Drug Safety and received an honorarium from Organon for contributing to an expert panel. RGB has received investigator-initiated research funding from the National Institutes of Health, including as co-investigator on one study for which aspirin was donated by Bayer. JMG has received investigator-initiated research funding and support as Principal Investigator from National Institutes of Health, BASF, DSM Pharmaceuticals, Wyeth Pharmaceuticals, McNeil Consumer Products and Pliva; received honoraria from Bayer and Pfizer for speaking engagements, and is a consultant for Bayer, McNeil Consumer Products, Wyeth Pharmaceuticals, Merck, Nutraquest and GlaxoSmithKline. JEB has received investigator-initiated research funding and support as Principal Investigator from the National Institutes of Health and Dow Corning Corporation; research support for pills and/or packaging from Bayer Heath Care and the Natural Source Vitamin E Association; honoraria from Bayer for speaking engagements; and serves on an external scientific advisory committee for a study by Procter & Gamble.
Ethics approval: All women gave written informed consent and the Institutional Review Board of Brigham and Women’s Hospital approved the Women’s Health Study.
The study sponsors had no role in the study design, the collection, analysis and interpretation of data, the writing of the report, and the decision to submit the paper for publication.
TK had full access to all the data in the study and takes responsibility for the integrity of the data, the accuracy of the data analysis and for the decision to submit for publication.
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