Risk factors for atopic and non-atopic asthma in school-aged children from high, and low and middle income countries

This is the authors' abstract. We don't add key points for this paper.

Background It is well established that there are different asthma phenotypes, but whereas determinants of atopic asthma are well studied, little is known about non-atopic asthma. We compared risk factors for atopy, atopic asthma (AA) in atopics, and non-atopic asthma (NAA) in non-atopics, in children in a wide variety of countries. Methods Using four studies, across 23 countries, we assessed asthma status and atopy (skin prick tests) for children aged 6-17, plus risk factors from housing, heating, pets, family, diet, and air-quality categories. Using mixed effects logistic regression models we assessed 4 pathways to asthma: Pathway 1: comparing NAA with non-atopic non-asthma (risk factors for NAA); Pathway 2: comparing atopic non-asthma with non-atopic non-asthma (risk factors for atopy); Pathway 3: comparing AA with atopic non-asthma (risk factors for AA); Pathway 4: comparing AA with non-atopic non-asthma (risk factors for atopy and AA together). Results Our final sample of 32741 children comprised 67% non-atopic non-asthmatics, 15% atopic non-asthmatics, 8% with AA and 10% with NAA. Risk factors were similar for AA in atopic individuals and NAA in non-atopic individuals (Pearson’s correlation r=0.81). In contrast, risk factors for atopy in non-asthmatics differed from those for AA in atopic individuals (r=-0.06). Discussion These findings indicate that although atopy increases the risk of asthma, the risk factors for subsequently developing asthma are generally the same in atopics and non-atopics. This raises important questions about the role of atopy in asthma, particularly whether it is an inherent part of the aetiological process or is coincidental. Key messages It is well established that there are different phenotypes of asthma but little is known about risk factors for non-atopic asthma. Using a novel approach, we found that lifestyle and environmental risk factors for developing asthma are generally similar in atopic children and non-atopic children but the risk factors for atopy are quite different. ur findings suggest that atopy and asthma may be coincidental in a large proportion of children who are defined as having atopic asthma. This has important implications for our understanding of the causes and mechanisms of different asthma phenotypes, and therefore prevention and treatment of asthma.