Fall Asthma Frequency Related to the Start of School

Neil W. Johnston, MSC, of St. Joseph's Healthcare and McMaster University, Hamilton, Ontario, Canada and colleagues were head researchers on the project and looked to determine the sequence of timing for September asthma hospitalization epidemics in children and adults, and determine whether school-age children transmit the viral infections that often lead to asthma attacks in adults.

Researchers used Canadian hospital admission data from 1990 to 2002 for the study. Study participants were divided into three age groups: preschool children ages 2 to 4; school-age children 5 to 15 years old; and adults 16 to 49 years old. The researchers also divided Canada into four geographic ranges based on latitude.

Some of the findings include the following:

- On average, the epidemic peak for school-age children was 17.7 days after Labor Day (the day after the holiday is traditionally the beginning of the school year), 19.4 days after Labor Day for preschool children and 24 days after Labor Day for adults.

- Timing of the asthma exacerbation peak from north to south was also consistent with differences in weather conditions and in-school allergen levels.

- The sequence of the epidemic remained consistent, suggesting the viral infections were transferred from the school-age children to the preschool children and adults with whom they were in contact.

- School-age children were the starting point for the viruses, with children ages 5 to 7 the leading group affected by the asthma epidemic. Researchers suggest this could be because they are not as resistant to the infections and because infections transmit easily from children to other children or adults because of children's social behavior.

- Rhinovirus infections are the leading cause of respiratory infections for children in the early fall. Between 80 to 85 percent of children with wheezing episodes test positive; half the adults with a wheezing episode also have rhinovirus infections.

Johnston and colleagues concluded that finding ways to prevent respiratory infections in children is a key component to lessening the annual asthma outbreak for all ages.

The research report, The September epidemic of asthma hospitalization: School children as disease vectors, was published in the March 2006 issue of the Journal of Allergy and Clinical Immunology (JACI), a peer-reviewed, scientific journal of the American Academy of Allergy, Asthma and Immunology.