Prevention of asthma during the first 5 years of life: a randomized controlled trial.

Background: Early life exposures may be important in the development of asthma and allergic disease.

Objective: To test house dust mite (HDM) avoidance and dietary fatty acid modification, implemented throughout the first 5 years of life, as interventions to prevent asthma and allergic disease.

Methods: We recruited newborns with a family history of asthma antenatally and randomized them, separately, to HDM avoidance or control and to dietary modification or control. At age 5 years, they were assessed for asthma and eczema and had skin prick tests for atopy.

Results: Of 616 children randomized, 516 (84%) were evaluated at age 5 years. The HDM avoidance intervention resulted in a 61% reduction in HDM allergen concentrations (microg/g dust) in the child's bed but no difference in the prevalence of asthma, wheeze, or atopy (P > .1). The prevalence of eczema was higher in the active HDM avoidance group (26% vs 19%; P = .06). The ratio of omega-6 to omega-3 fatty acids in plasma was lower in the active diet group (5.8 vs 7.4; P < .0001). However, the prevalence of asthma, wheezing, eczema, or atopy did not differ between the diet groups (P > .1).

Conclusion: Further research is required to establish whether other interventions can be recommended for the prevention of asthma and allergic disease.

Clinical Implications: House dust mite avoidance measures and dietary fatty acid modification, as implemented in this trial during infancy and early childhood, did not prevent the onset of asthma, eczema, or atopy in high-risk children.