Abstract and Introduction
Abstract
Extensive literature exists on potential risk factors for childhood asthma. To the authors' knowledge, no investigators have yet attempted to disentangle the effects of those determinants within a single study setting. The authors aimed to evaluate the independent effects of 47 potential determinants (from the prenatal, perinatal, and childhood periods) of asthma development in children within the first 10 years of life. From a Canadian birth cohort of 26,265 children (1990-2002), a 2-stage case-control study was conducted. In the first stage, 20 controls per case were selected from 3 administrative databases. In the second stage, selected mothers were mailed questionnaires for assessment of additional determinants. Increased risks of childhood asthma were found for ≥1 previous diagnosis of bronchopulmonary disease and atopic dermatitis in the child, oxygen administration after birth, prescription of antibiotics within the first 6 months of life, male gender, asthma during pregnancy, use of antibiotics during pregnancy, maternal receipt of social aid, paternal asthma, and asthma in siblings. Protective effects included use of intranasal corticosteroids during pregnancy, having a wood-burning fireplace, having pets in the home prior to the index date, breastfeeding, and day-care attendance. This study allowed the authors to identify, within a single setting, the most influential determinants of childhood asthma among 47 predictors assessed for the prenatal, perinatal, and childhood periods.
Introduction
The prevalence of childhood asthma has been increasing over the last few decades, as has its related burden. In addition to the personal and social impacts of childhood asthma, increases in emergency-room visits, hospitalizations, and missed school days due to asthma exacerbations in children have emphasized the need to understand the development of childhood asthma and identify its key determinants, especially modifiable ones.
The presence of asthma and atopy in the family, most importantly maternal history of asthma, is one of the many risk factors reported in the literature. Furthermore, the timing of exposure is also of interest, as there is evidence that some of the atopic response of the child could be primed in utero and influenced after birth.
However, while the literature on potential determinants of childhood asthma is extensive, results obtained are sometimes mitigated and/or could still be confounded, since most investigators have been providing risk estimates adjusted only for subsets of risk factors, leaving the estimates unadjusted for several other determinants. Furthermore, in some well-performed studies, investigators gathered data on a wide variety of potential determinants, but those data were analyzed by subgroup, thereby limiting the ability to disentangle the independent effects of those individual variables. The above-mentioned limitations could be due to the unavailability of necessary information or to small sample sizes, precluding the investigation of several determinants at the same time.
Thus, we conducted the current study to obtain a more complete picture of the development of childhood asthma. Using the rich source of data provided by large administrative health databases and a mailed questionnaire, we aimed at identifying the independent effects of 47 potential predictors, measured during pregnancy and after birth, on the incidence of asthma development in children within the first 10 years of life.