Asthma diagnosis and treatment
The Canadian Childhood Asthma Primary Prevention Study: Outcomes at 7 years of age

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Background

Avoidance of any one of the individual risk factors associated with childhood asthma has not been successful in preventing its development.

Objective

The purpose of this study is to determine the effectiveness of a multifaceted intervention program for the primary prevention of asthma in high-risk infants at 7 years of age.

Methods

Five hundred forty-five high-risk infants with an immediate family history of asthma and allergies were prospectively randomized into intervention or control groups prenatally. Intervention measures introduced before birth and during the first year of life included avoidance of house dust, pets, and environmental tobacco smoke and encouragement of breast-feeding with delayed introduction of solid foods. Assessment of outcomes at 7 years consisted of examination by pediatric allergists, methacholine inhalation tests, and allergy skin tests.

Results

At 7 years, 469 of the 545 children were contacted, and 380 returned for further assessment. The prevalence of pediatric allergist–diagnosed asthma was significantly lower in the intervention group than in the control group (14.9% vs 23.0%; adjusted risk ratio, 0.44; 95% CI, 0.25-0.79). The prevalence of allergic rhinitis, atopic dermatitis, atopy (defined as positive skin test reactions to any common allergen), and bronchial hyperresponsiveness (defined as the provocative concentration of methacholine that induced a 20% decrease in FEV1 from a postsaline value of less than 7.8 mg/mL) were not significantly different between the 2 groups. The prevalence of asthma (defined as wheeze without colds and the presence of bronchial hyperresponsiveness) was also significantly lower in the intervention group compared with the control group (12.9% vs 25.0%; adjusted risk ratio, 0.39; 95% CI, 0.22-0.71).

Conclusion

The multifaceted intervention program was effective in reducing the prevalence of asthma in high-risk children at 7 years of age.

Section snippets

Study population

The cohort has been described in previous reports.6, 7 Briefly, infants at high risk for asthma development, defined as those with at least one first-degree relative with asthma or 2 first-degree relatives with other IgE-mediated allergic diseases (atopic dermatitis, seasonal or perennial allergic rhinitis, or food allergy), were identified during the mother's third trimester of pregnancy. Families were randomly allocated to our multifaceted intervention (n = 279) or to the control group (n = 266).

Results

The characteristics at baseline of the 380 children who returned for an interview and physical examination at 7 years of age are shown in Table I. Except for a greater percentage of mothers in the control group having postsecondary education, personal and family characteristics at baseline of those who came in for interview and examination at 7 years of age were not different from the characteristics of those who only completed a questionnaire over the telephone and also were not different from

Discussion

This is a study of the outcomes at 7 years of a prospective, randomized controlled trial with a multifaceted intervention program to decrease exposure to allergens (both inhaled and ingested) and environmental tobacco smoke in the first year of life of infants at high risk for the development of asthma because of their family history. We have previously reported a significant reduction in possible asthma (defined as having, over the past 12 months, at least 2 distinct episodes of cough, each

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Supported by the Canadian Institute of Health Research, the British Columbia Lung Association, and the Manitoba Medical Service Foundation.

Disclosure of potential conflict of interest: A; authors—none disclosed.

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