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Am J Respir Crit Care Med. 2017 Jul 15;196(2):150-158. doi: 10.1164/rccm.201609-1966OC.

Preventing Severe Asthma Exacerbations in Children. A Randomized Trial of Mite-Impermeable Bedcovers.

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1 Division of Infection, Immunity and Respiratory Medicine, Manchester Academic Health Sciences Centre, University of Manchester, Manchester, United Kingdom.
2 University Hospital of South Manchester, Manchester, United Kingdom.
3 Royal Manchester Children's Hospital, Central Manchester University Hospitals National Health Service Foundation Trust, Manchester, United Kingdom.
4 National Institute for Health Research South Manchester Respiratory and Allergy Clinical Research Facility, University Hospital of South Manchester, United Kingdom; and.
5 Department of Paediatrics, Imperial College London, London, United Kingdom.



Allergen exposure in sensitized individuals with asthma interacts with viruses to increase the risk of asthma exacerbation.


To evaluate the use of house dust mite-impermeable bedding and its impact on severe asthma exacerbations in children.


We randomized mite-sensitized children with asthma (ages 3-17 yr) after an emergency hospital attendance with an asthma exacerbation to receive mite-impermeable (active group) or control (placebo group) bed encasings.


Over a 12-month intervention period, the occurrence of severe asthma exacerbations was investigated. Of 434 children with asthma who consented, 286 (mean age, 7.7 yr; male sex, 65.8%) were mite sensitized, and 284 were randomized (146 to the active group and 138 to the placebo group). At 12 months, significantly fewer children in the active group than in the placebo group had attended the hospital with an exacerbation (36 [29.3%] of 123 vs. 49 [41.5%] of 118; P = 0.047). In the multivariable analysis, the risk of emergency hospital attendance was 45% lower in the active group (hazard ratio, 0.55; 95% confidence interval [CI], 0.36-0.85; P = 0.006) than in the placebo group. The annual rate of emergency hospital attendance with exacerbations was 27% lower in the active group than in the placebo group, but this did not reach significance (estimated marginal mean [95% CI], active, 0.38 [0.26-0.56] vs. placebo, 0.52 [0.35-0.76]; P = 0.18). No difference between the groups in the risk of prednisolone use for exacerbation was found (hazard ratio, 0.82; 95% CI, 0.58-1.17; P = 0.28).


Mite-impermeable encasings are effective in reducing the number of mite-sensitized children with asthma attending the hospital with asthma exacerbations but not the number requiring oral prednisolone. This simple measure may reduce the health care burden of asthma exacerbations in children. Clinical trial registered with (ISRCTN 69543196).


allergens; asthma; avoidance; child; exacerbations

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