BREASTFEEDING AND THE PREVALENCE OF ASTHMA AND WHEEZE IN CHILDREN : ANALYSES FROM THE THIRD NATIONAL HEALTH AND NUTRITION EXAMINATION SURVEY , 1988 – 1994

Nja F, Nystad W, Hetlevik O, Lodrup Carlsen KC, Carlsen K-H. Arch Dis Child. 2003;88:566–569 Purpose of the Study. To determine whether a history of otitis media (OM) and respiratory tract infection (RTI) was associated with allergic sensitization and asthma among school-aged children. Study Population. A total of 4585 children from 4 cities in Norway were surveyed for this study. Children recruited from 2 cities had the diagnosis of asthma or had wheezed without the diagnosis of asthma in the past 12 months. In the third city, children were randomly recruited. Control groups came from the same areas. The final study population included 502 children with complete data sets. Group 1 (n 166) included those with current asthma or previous asthma, group 2 (n 155) included those who had wheezed within the past year but had no diagnosis of asthma, and group 3 (n 181) included those without asthma or wheezing. Methods. The initial survey was from the International Study of Asthma and Allergies in Childhood. A second clinical study with the study groups investigated early exposures and health outcomes. The children also underwent skin prick testing and clinical examinations. Skin prick testing was performed with house dust mites, mold, animal dander, birch tree pollen, timothy grass pollen, mugwort pollen, cow’s milk, and egg. Questions addressed OM and RTI, all involving recall of physician diagnoses. Information was also obtained about confounders such as breastfeeding, day care, and smoke exposure. Results. The prevalence of allergic sensitization was different among children of atopic parents versus nonatopic parents (49.3% vs 31.9%). The prevalence of OM did not differ significantly between those born of atopic versus nonatopic parents (8.0% vs 7.4%). The associations between OM with or without RTI during infancy and allergic sensitization among school-aged children of atopic parents demonstrated odds ratios of 0.13 and 0.31, respectively. The association between RTI and asthma among schoolaged children depended on whether lower RTI was included. Among children of nonatopic parents, a history of RTI/lower RTI was significantly associated with a history of asthma (odds ratio: 4.21). There was no association among children born to atopic parents. Confounding variables had no effect on this relationship. Conclusions. In this study, a history of OM in infancy was negatively associated with allergic sensitization among school-aged children born to atopic parents, whereas a history of lower RTI was positively associated with asthma among children of nonatopic parents. Reviewer’s Comments. The “hygiene hypothesis” has been put forth as a potential explanation for the increase in allergic conditions. Studies on RTIs have yielded inconsistent results with respect to allergic sensitization. However, studies on RTI as a risk factor for asthma seem to be more consistent in their conclusions. The finding of less allergen sensitization among those with OM in infancy is new. The strongest association between subsequent asthma and early childhood infections was found among nonatopic children. This should be an area of continuing investigation, ideally with large prospective studies.