Reduced risk of wheezing in children using feather pillows is confirmed

BMJ 1997;314:518 (15 February)

Letters

Reduced risk of wheezing in children using feather pillows is confirmed

Editor–T J Kemp and colleagues' study of levels of miteallergen in pillows¹ was prompted by the unexpected findingsof our case-control study in which feather pillows were associatedwith a reduced risk of severe childhood asthma.² The cases andcontrols in our analysis were drawn from a larger survey, anda different subsample of the survey respondents underwent skinprick testing with extracts of Der p I, mixed grass pollen,and cat fur, as described elsewhere.³ The subsample includedgroups at high and low risk of hay fever, as predicted fromfamily size and structure.³ The questionnaire used in our case-control studywas posted to the parents of the 727 children who were skintested, and replies were received for 617 (85%). We presenthere the results for 523 children, whose parents denied havingmade alterations to the child's bedroom (as defined previously²).

Table 1 shows the proportion of children sleeping on a featherpillow by history of wheezing and reaction to Der p I on skinprick testing. Only 30 children with a weal <1 mm in diameterto Der p I had a visible weal (1 mm) to either grass pollenor cat fur, so the results are similar if categorised by anypositive skin prick reaction.

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Table 1 Number (percentage) of children who used feather pillows by history of wheezing and sensitisation to house dust mite^*

Use of a feather pillow was similar among the 353 children withno history of wheezing and 73 children with inactive wheezein 1991 but was significantly reduced among the 97 childrenwith wheeze in the past year in 1991. The odds ratio comparingall current wheezers to never wheezers, and feather pillowsto non-feather pillows, was 0.46 (95% confidence interval 0.26to 0.81) (P=0.006). When 26 more severe wheezers were excludedthe odds ratio was 0.56 (0.30 to 1.04) (P=0.07). The inverseassociation of use of a feather pillow with current wheezingwas of similar strength among children with and without skinprick reactions to Der p I.

These observations on essentially new data confirm our earlierfindings of a reduced risk of wheezing, and particularly severewheezing, in children using feather pillows.² Differences innocturnal exposure to mite allergen, as proposed by Kemp andcolleagues, are unlikely to explain the effect of pillows, whichis of similar magnitude in children with and without sensitisationto house dust mite. The observation that levels of mite allergenare no higher in feather pillows than in synthetic substitutes,however, contributes to the equipoise necessary before a morerigorous evaluation of different types of pillow by controlled clinicaltrial is contemplated.

David Strachan, Reader in epidemiology,^a Iain M Carey, Statistician ^a

^a Department of Public Health Sciences, St George's Hospital Medical School, London SW17 0RE

Kemp TJ, Siebers RW, Fishwick D, O'Grady GB, Fitzharris P, Crane J. House dust mite allergen in pillows. BMJ 1996;313:916. (12 October.) [Free Full Text]
Strachan DP, Carey IM. The home environment and severe asthma in adolescence: a population based case-control study. BMJ 1995;311:1053-6. [Abstract/Free Full Text]
Strachan DP, Taylor EM, Carpenter RG. Family structure, neonatal infection and hay fever in adolescence. Arch Dis Child 1996;74:422-6.

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Increased house dust mite allergen in synthetic pillows may explain increased wheezing: Julian Crane, Trudi Kemp, Robert Siebers, Natalie Rains, David Fishwick, and Penny Fitzharris
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Crane, J., Kemp, T., Siebers, R., Rains, N., Fishwick, D., Fitzharris, P. (1997). Increased house dust mite allergen in synthetic pillows may explain increased wheezing. BMJ 314: 1763-1763 [Full text]