Viral respiratory infections and exposure to environmental constituents such as tobacco smoke are known or suspected to trigger wheezing/asthma exacerbations in children. However, few population-based data exist that examine the relationship between wheezing triggered by viral respiratory infections and environmental exposures. In this investigation we used population-based data to evaluate differences in exposures between symptomatic middle school-age children who did and did not report wheezing triggered by viral respiratory infections. As part of the North Carolina School Asthma Survey (NCSAS), a 66-question data instrument was used to collect information from children enrolled in North Carolina public middle schools during the 1999-2000 school year. Associations between exposures and upper respiratory infection-triggered wheezing (URI-TW) among symptomatic children were examined using adjusted prevalence odds ratios (PORs). Video methods developed for the International Study of Asthma and Allergies in Childhood were used to assess wheezing. Among the 33,534 NCSAS symptomatic participants, positive associations were observed between most exposures and URI-TW. Reported presence of all allergy variables (PORs ranging from 2.11 to 2.45) was more strongly associated with URI-TW than either smoking or other exposures. Presence of URI-TW was higher at increasing levels of tobacco smoke exposure, but no apparent dose-response effect was observed for other indoor air pollutants. URI-TW in middle school children is most associated with reported allergen sensitivity, relative to other asthma risk factors and environmental exposures. Data from this investigation may be useful in developing assessment, screening, and targeting strategies to improve asthma and wheezing management in children. Key words: allergies, asthma, childhood, environment, exposures, infections, respiratory, rhinovirus, wheezing.
An estimated 5 million U.S. children per year suffer from asthma, the most common chronic childhood illness in the United States (AAANPO 2000). These numbers may underestimate the impact of the disease because childhood asthma is believed to be both widely underdiagnosed and under-treated (Pearce et al. 1998). Diagnosed asthma rates are highest in children compared with other age groups, and asthma is thought to have increased 92% in U.S. children over the past decade (AAANPO 2000).
Exacerbations of asthma are the major cause of morbidity and mortality in asthmatic children (Johnston 1998; Johnston et al. 1996). Clinical evidence suggests that viral infections, rather than bacterial infections, play the major role in asthma exacerbation caused by upper respiratory infections (URIs) (Abramson et al. 1995; Busse et al. 1997; Johnston 1998; Pearce et al. 1998; Weiss 1998). In addition, a study by Sarafino et al. (1998) examined the impact of various triggers for asthma symptoms at various ages and found that, of all triggers examined, the impact of respiratory infections declines the most with age in children. They concluded that as children get older, asthma episodes are more likely to be triggered by factors such as exercise and allergy, problems.
Exposure to various constituents including tobacco smoke, airborne allergens, dust mites, mold, and other indoor air pollutants is known or suspected to trigger wheezing or asthmatic exacerbations in children (Pearce et al. 1998). Such exposures may have increasing importance to the lives of U.S. children, most of whom spend at least 90% of their time indoors (Bjorksten 1996). Despite this increased importance, few population-based data exist that examine whether exposure to environmental factors is different in symptomatic children whose wheezing is triggered by URIs (URI-TW) compared with children for whom URIs are not a trigger for their wheezing exacerbations.
The purpose of this investigation is to use population-based, self-reported data and internationally standardized methods from the International Study of Asthma and Allergies in Childhood (ISAAC) to evaluate whether differences in environmental exposures and asthma risk factors exist between currently symptomatic middle school-age children who continue to experience URI-TW and children for whom URIs are not a trigger. …