Environmental and Occupational Disorders
Eighteen-month outcomes of house dust mite avoidance and dietary fatty acid modification in the childhood asthma prevention study (CAPS),☆☆

https://doi.org/10.1067/mai.2003.36Get rights and content

Abstract

Background: Observational studies have linked house dust mite (HDM) exposure and dietary fatty acid intake with asthma in childhood. However, definitive evidence of their role in the etiology of asthma requires a randomized controlled trial. Objective: We hypothesized that the incidence of asthma and allergy in high-risk children would be reduced by avoidance of HDM allergens, supplementation with omega-3 fatty acids, or the combination of these strategies. We present the results of an interim analysis reporting outcomes assessed at 18 months. Methods: A total of 616 pregnant women were randomized to an HDM avoidance intervention, comprising the use of impermeable mattress covers and an acaricide or control and the use of an oil supplement, margarines, and cooking oils containing high levels of omega-3 fatty acids or control. Atopic status was measured by skin prick testing. Symptoms, diagnoses, and medication histories were elicited by means of parental interviews. Results: The diet intervention resulted in a 9.8% absolute reduction (95% CI, 1.5-18.1; P = .02) in the prevalence of any wheeze and a 7.8% absolute reduction (95% CI, 0.5-15.1, P = .04) in prevalence of wheeze of >1 week, but it had no effect on serum IgE, atopy, or doctors' diagnosis of asthma. The HDM avoidance intervention did not affect these outcomes but was associated with a lower use of oral steroids. Conclusion: Increasing dietary omega-3 fatty acids might have a beneficial effect on the prevalence of wheeze during the first 18 months of life. Follow-up to age 5 years, when the effect of the interventions on asthma risk will be assessed, is underway. (J Allergy Clin Immunol 2003;111:162-8.)

Section snippets

Methods

The study hypotheses were tested in a parallel-group randomized controlled trial in which the 2 interventions were tested separately and then together through use of a factorial design. The details of the study design and recruitment procedure, which have been reported elsewhere,7, 8 are described briefly here.

Results

Fig 1 shows the trial profile.

. CAPS trial profile.

Fifty-six participants withdrew after randomization and before the 12-month visit, and an additional 6 participants withdrew before the 18-month assessment. A total of 554 participants completed the 18-month assessment. Table I shows the characteristics of the participants and their families in each of the 4 intervention groups.

. Demographic data for all groups

CharacteristicDIet interventionHouse dust mite intervention
Control N = 275Active N = 279

Discussion

The early results of this study suggest that increasing omega-3 fatty acids in the diet in the first 18 months of life might have a beneficial effect on wheezing in high-risk infants. The prevalence of parental report of wheeze-ever was 9.8% lower and the prevalence of wheeze for >1 week 7.8% lower in the active diet intervention group. The prevalence of other indicators of wheeze and allergic disease, such as rhinitis, also tended to be reduced in this group. However, we found no benefit for

Acknowledgements

The CAPS Study senior investigators are Jennifer K. Peat, Guy B. Marks, Craig M. Mellis and Stephen R. Leeder. Associate investigators are Euan R. Tovey and Karen Webb. The Study Coordinator is Seema Mihrshahi. The authors wish to thank the CAPS research team involved in the study. Data have been collected by Anne Tattam, Samantha Forbes, Nicola Vukasin, Craig Wainwright, William Krause, and Natalia Knezevic. Allergen assays were performed by Carl H. Vanlaar and Sally Criss. Fatty acid and

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Supported in part by the National Health and Medical Research Council of Australia, New South Wales Health Department, The Children's Hospital at Westmead, and the Cooperative Research Centre for Asthma. Contributions of goods and services were made by Allergopharma Joachim Ganzer KG Germany, John Sands Australia, Hasbro, Refrigerated Roadways, and AstraZeneca. Goods were provided at reduced cost by Auspharm, Allersearch, Meadow Lea Foods, and Clover Corporation.

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Reprint requests: Seema Mihrshahi, MPH, Clinical Epidemiology Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, NSW 2145, Australia.

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