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Exposure to dust mite allergen and endotoxin in early life and asthma and atopy in childhood

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Background

There has been no longitudinal study of the relation between concurrent exposure to dust mite allergen and endotoxin in early life and asthma and atopy at school age.

Objectives

To examine the relation between exposure to dust mite allergen and endotoxin at age 2 to 3 months and asthma, wheeze, and atopy in high-risk children.

Methods

Birth cohort study of 440 children with parental history of atopy in the Boston metropolitan area.

Results

In multivariate analyses, early exposure to high levels of dust mite allergen (≥10 μg/g) was associated with increased risks of asthma at age 7 years (odds ratio [OR], 3.0; 95% CI, 1.1-7.9) and late-onset wheeze (OR, 5.0; 95% CI, 1.5-16.4). Exposure to endotoxin levels above the lowest quartile at age 2 to 3 months was associated with reduced odds of atopy at school age (OR, 0.5; 95% CI, 0.2-0.9). In contrast with its inverse association with atopy, endotoxin exposure in early life was associated with an increased risk of any wheeze between ages 1 and 7 years that did not change significantly with time (hazard ratio for each quartile increment in endotoxin levels, 1.23; 95% CI, 1.07-1.43).

Conclusion

Among children at risk of atopy, early exposure to high levels of dust mite allergen is associated with increased risks of asthma and late-onset wheeze. In these children, endotoxin exposure is associated with a reduced risk of atopy but an increased risk of wheeze.

Clinical implications

Early endotoxin exposure may be a protective factor against atopy but a risk factor for wheeze in high-risk children.

Section snippets

Study population

Study participants were recruited between September 1994 and August 1996. The screening and recruitment of families have been described in detail elsewhere.10, 11 In brief, eligibility criteria included residence in the Boston metropolitan area; maternal age ≥18 years; and history of hay fever, asthma, or allergies in at least 1 of the child's parents. Families were not screened if the newborn was hospitalized in the intensive care unit, if his/her gestational age was < 36 weeks, or if he/she

Results

The characteristics of the 498 study subjects have been described in detail elsewhere.26, 27 Of the 498 study participants, 440 (88.4%) were followed to the age of 7 years, and 271 (54.4%) had an assessment of allergic sensitization at school age. There was no statistically significant difference in exposure to endotoxin or dust mite allergen at age 2 to 3 months among children at baseline, children followed up to age 7 years, and children with assessment of allergic sensitization (Table I).

Discussion

Sporik et al1 first reported a strong association between exposure to ≥ 10 μg/g house dust mite in infancy and asthma at age 11 years among children with parental history of asthma or hay fever. That study was limited by small sample size (n = 59) and loss of follow-up of study participants. Our finding of a positive association between early dust mite allergen exposure and asthma in a larger cohort of children precisely replicate the results of Sporik et al,1 and together with those of a

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    Supported by grants AIEHS35786 and ES07036 from the National Institutes of Health to D.R.G. and D.K.M. J.C.C. is supported by grants HL04370, HL079966, and HL073373 from the National Institutes of Health.

    Disclosure of potential conflict of interest: D. R. Gold has lectured for Inbio. The rest of the authors have declared that they have no conflict of interest.

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