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Evidence of a Causal Role of Winter Virus Infection during Infancy in Early Childhood Asthma

¹ Division of Allergy, Pulmonary and Critical Care Medicine, ² Department of Medicine, ³ Department of Biostatistics, ⁴ Center for Health Services Research, ⁵ Institute for Medicine and Public Health, ⁶ Department of Preventive Medicine, ⁷ Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee

Correspondence and requests for reprints should be addressed to Tina V. Hartert, M.D., M.P.H., 6107 Medical Center East, Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232-8300. E-mail: tina.hartert{at}vanderbilt.edu

Rationale: Bronchiolitis during infancy is associated with an increased risk of childhood asthma. Whether winter viral infections cause asthma or are a manifestation of a predisposition to asthma development is unknown.

Objectives: To study the relationship of winter virus infection during infancy and the development of childhood asthma.

Methods: We studied over 95,000 infants born between 1995 and 2000 and followed through 2005 who were enrolled in the Tennessee Medicaid program from birth through early childhood to determine whether infant birth in relationship to the winter virus peak alters the risk of developing early childhood asthma.

Measurements and Main Results: Among 95,310 children studied during five winter virus seasons from birth through early childhood, the risk of developing asthma tracked with the timing of infant birth in relationship to the winter virus peak. Infant birth approximately 4 months before the winter virus peak carried the highest risk, with a 29% increase in odds of developing asthma compared with birth 12 months before the peak (adjusted odds ratio, 1.29; 95% confidence interval, 1.19–1.40). Infant age at the winter virus peak was comparable to or greater than other known risk factors for asthma.

Conclusions: Timing of birth in relationship to winter virus season confers a differential and definable risk of developing early childhood asthma, establishing winter virus seasonality as a causal factor in asthma development. Delay of exposure or prevention of winter viral infection during early infancy could prevent asthma.

Key Words: asthma • respiratory winter virus infection • timing of birth

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Bronchiolitis during infancy is associated with an increased risk of childhood asthma. Whether common respiratory viruses, which infect all infants, cause asthma or whether infection is a marker of those predisposed to developing asthma is unknown. What This Study Adds to the Field Timing of birth in relationship to the annual winter virus peak predicts an infant's likelihood of developing childhood asthma. This study provides strong evidence for a causal relationship of winter viruses with early childhood asthma.

 

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Early-Life Viral Bronchiolitis in the Causal Pathway of Childhood Asthma: Is the Evidence There Yet?

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AJRCCM 2008 178: 1097-1098. [Full Text]