Asthma and lower airway disease
Do boys do the atopic march while girls dawdle?

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Background

The atopic march hypothesis suggests that infants with eczema are at increased risk of asthma. Others argue that eczema is not a risk factor for asthma unless there is also sensitization or early wheezing.

Objective

To examine the role of infantile eczema as a predictor of risk of childhood asthma, while allowing for the effects of early wheeze, sensitization, and sex, both as independent effects and possible effect modifiers.

Methods

A total of 620 infants with a family history of allergic disease was recruited. Eczema and wheeze was prospectively documented to 2 years of age. Sensitization was determined by skin prick tests at 6, 12, and 24 months to 6 common food and inhalant allergens. Interviews were conducted at 6 and 7 years to ascertain current asthma.

Results

Sufficiently complete data were available for 403 children. Eczema within the first 2 years of life was clearly associated with an increased risk of childhood asthma in boys (adjusted odds ratio, 2.45; 95% CI, 1.31-4.46) but not in girls (odds ratio, 0.88; 95% CI, 0.43-1.77; P for interaction = .031) even with adjustment for the effects of early allergic sensitization and wheeze. If these relationships are causal, an intervention to prevent eczema in boys might reduce the incidence of childhood asthma by as much as 28%.

Conclusion

Eczema in the first 2 years of life is associated with an increased risk of childhood asthma in boys, but there is no evidence of this in girls.

Section snippets

Study population

Before birth, the MACS recruited 620 infants born between 1990 and 1994 in Melbourne, Australia. The recruitment process has been described in more detail elsewhere.12 The study was approved by Mercy Maternity Hospital's Human Research Ethics Committee. Informed consent was obtained from all mothers. Infants were eligible to be enrolled in MACS if 1 or more of their first-degree family members had eczema, asthma, allergic rhinitis, or severe food allergy.

Data collection

Baseline details were recorded during

Study population

Of the 620 MACS infants, 544 (88%) were followed to 2 years of age. Of these infants, 110 had missing SPT data, so sensitization status could not be determined. Of the remaining 434 infants, 403 were followed up at either 6 or 7 years of age (Fig 1). Further details of the cohort have been published elsewhere.7, 12, 14

Eczema in the first 2 years of life

Of the 403 infants with complete follow-up in the first 2 years of life and childhood follow-up (6 and/or 7 years), almost half (n = 193; 48%) developed eczema within the first 2

Discussion

Our observations in this prospective birth cohort of infants with a family history of allergic disease suggest that eczema in early life is associated with a clearly increased risk of childhood asthma only in boys. In girls, the evidence for an association between eczema in infancy and childhood asthma was weak. Boys with early-onset and/or severe eczema were at the greatest risk of childhood asthma, whereas there was no apparent increased risk in girls, regardless of age of onset and severity.

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    A.J.L. is supported by Dairy Australia, Cooperative Research Centre for Asthma, and VicHealth. Initial development of the Melbourne Atopy Cohort Study was supported by Nestlé Australia. The Asthma Foundation of Victoria supported the 10-year follow-up.

    Disclosure of potential conflict of interest: The authors have declared that they have no conflict of interest.

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