Alexander C. Ferguson

To cite this article: Carlsten C, Ferguson A, Dimich‐Ward H, Chan H, DyBuncio A, Rousseau R, Becker A, Chan‐Yeung M. Association between endotoxin and mite allergen exposure with asthma and specific sensitization at age 7 years in high‐risk children. Pediatr Allergy Immunol 2011; 22: 320–326. The role of endotoxin and house dust mite allergen (HDM) in allergen sensitization and asthma is unclear. The timeframe of exposure and asthma assessment appears critical. We aimed to determine, in children at 7 yr of age, the association between current exposure to endotoxin and HDM and risks of recurrent wheeze, paediatric allergist diagnosed asthma and allergen sensitization. Three hundred and eighty children who had an increased risk of asthma because of family background were assessed at age 7 yr by a questionnaire‐standardized interview, allergen skin testing and clinical examination by a paediatric allergist. Dust samples were collected from their homes and analysed for levels of endotoxin and HDM (Der p 1 and Der f 1). Levels of endotoxin in dust samples were associated with protection from paediatric allergist diagnosed asthma with inhaled steroid use (OR 0.69, 95% CI 0.53–0.91) and specific sensitization to dog allergen (OR 0.68, 95% CI 0.51–0.90) at the age of 7 yr; both endotoxin and HDM were associated with decreased risk of sensitization to dog allergen. In high‐risk children at age 7, endotoxin levels were associated with decreased sensitization to dog, as well as with decreased asthma.

Wang H‐Y, Pizzichini MMM, Becker AB, Duncan JM, Ferguson AC, Greene JM, Rennie DC, Senthilselvan A, Taylor BW, Sears MR. Disparate geographic prevalences of asthma, allergic rhinoconjunctivitis and atopic eczema among adolescents in five Canadian cities.Pediatr Allergy Immunol 2010: 21: 867–877.© 2010 John Wiley & Sons A/S To assess concordance of prevalence rates of asthma, allergic rhinoconjunctivitis and atopic eczema symptoms among adolescents in five Canadian cities. The International Study of Asthma and Allergies in Childhood Phase 3 written questionnaires were answered by 8334 adolescents aged 13 to 14 in Vancouver, Saskatoon, Winnipeg, Hamilton and Halifax, Canada. Prevalence rates of current symptoms ranged from 13.7–33.0% for wheezing, 14.6–22.6% for allergic rhinoconjunctivitis and 8.2–10.4% for atopic eczema. Using Hamilton as reference, the prevalence of wheezing was significantly higher in Halifax (OR = 1.58; 95% CI 1.36–1.84) and Saskatoon (1.27; 1.07–1.50) and significantly lower in Vancouver (0.51; 0.44–0.59). In contrast, allergic rhinoconjunctivitis was significantly more prevalent in Winnipeg (1.39; 1.16–1.68) and Halifax (1.36; 1.14–1.61) and trended lower in Saskatoon (0.81; 0.66–1.00). Atopic eczema was significantly more prevalent in Winnipeg (1.31; 1.01–1.69) and Vancouver (1.28; 1.04–1.58). Multivariable logistic regression analyses showed the region of residence, being born in Canada, recent use of acetaminophen and heavy exposure to traffic exhaust were significantly associated with all three allergic conditions, while obesity and having two or more smokers at home was only associated with increased risk for wheezing. Chinese ethnicity decreased that risk. Among five Canadian centres, the highest prevalence rates of allergic rhinoconjunctivitis or atopic eczema were not observed in the same regions as the highest prevalence rates of wheezing. This disparity in regional variations in the prevalence rates suggests dissimilar risk factors for the development or expression of wheezing (asthma), allergic rhinoconjunctivitis and atopic eczema.

Carlsten C, Dimich‐Ward H, Becker AB, Ferguson A, Chan HW, DyBuncio A, Chan‐Yeung M. Indoor allergen exposure, sensitization, and development of asthma in a high‐risk birth cohort.Pediatr Allergy Immunol 2010: 21: e740–e746.© 2010 John Wiley & Sons A/S Contradictory findings have been observed for the association of house dust mite (HDM), cat, and dog allergen exposure with sensitization and asthma. We sought to determine the relationship between exposures to these allergens, at various points during early childhood, and specific sensitization and asthma at age 7 in a high‐risk birth cohort. As part of a multi‐faceted Canadian intervention program for the primary prevention of asthma in high‐risk infants, children were assessed by pediatric allergists at age 7 for asthma and underwent allergy skin prick testing. House dust samples were analyzed for HDM, cat, and dog allergen levels at several time points during years 1 and 7 of life. Multiple logistic regression analyses were carried out for the combined cohort and separately for the control and intervention groups. Exposure to a higher level of HDM allergen in year 1 or year 7 was associated with a higher risk of year 7 sensitization to HDM but not asthma. Exposure to higher levels of cat allergen in year 1 or year 7 did not affect the risk of year 7 sensitization to cat or asthma. Dog ownership, or exposure to higher levels of dog allergen in year 1 or year 7, did not affect the risk of year 7 sensitization to dog; however, year 7 dog allergen exposure (intervention group only) or ownership was associated with increased year 7 asthma risk. Our findings suggest that in high‐risk children, there are allergen‐specific associations of exposure with sensitization and with asthma; early life–elevated HDM exposure was associated with risk of sensitization but not asthma while the opposite was true for dog exposure.

There is considerable interest in identifying children at high risk for developing atopic diseases for primary prevention. This study evaluates risk factors for detectable cord blood IgE and assesses CB‐IgE in predicting asthma and other IgE‐mediated allergic diseases in children at high risk because of family history. Cord blood was obtained as part of a randomized controlled trial assessing the efficacy of an intervention program in the primary prevention of IgE‐mediated allergic diseases. CB‐IgE was measured and the degree to which this was associated with perinatal risk factors was assessed. The cohort was then evaluated for atopic disorders at 7 yrs of age to assess the predictive value of CB‐IgE. Fifty‐five (19.3%) of infants had detectable CB‐IgE (≥0.5 kU/l). Maternal atopy and birth in winter months were risk factors associated with detectable CB‐IgE. CB‐IgE was found to be significantly associated with allergic sensitization (OR 2.22; 95% CI 1.11, 4.41) and recurrent wheeze at 7 yrs (OR 2.51, 95% CI 1.09, 5.76) but not with other outcomes. CB‐IgE may be a useful measure for identifying children at high risk of atopic diseases for the purpose of primary prevention.

Background: Studies of the prevalence of asthma among migrating populations may help in identifying environmental risk factors. Methods: We analyzed data from Vancouver, Canada, and from Guangzhou, Beijing and Hong Kong, China, collected during phase 3 of the International Study of Asthma and Allergies in Childhood. We subdivided the Vancouver adolescents according to whether they were Chinese immigrants to Canada, Canadian-born Chinese or Canadian-born non-Chinese. We compared the prevalence of asthma and wheezing among Chinese adolescents born in Canada, Chinese adolescents who had immigrated to Canada and Chinese adolescents living in China. Results: Of 7794 Chinese adolescents who met the inclusion criteria, 3058 were from Guangzhou, 2824 were from Beijing, and 1912 were from Hong Kong. Of 2235 adolescents in Vancouver, Canada, 475 were Chinese immigrants, 617 were Canadian-born Chinese, and 1143 were Canadian-born non-Chinese. The prevalence of current wheezing among boys ranged from 5.9% in Guangzhou to 11.2% in Canadian-born Chinese adolescents. For girls, the range was 4.3% in Guangzhou to 9.8% in Canadian-born Chinese adolescents. The prevalence of ever having had asthma ranged from 6.6% to 16.6% for boys and from 2.9% to 15.0% for girls. Prevalence gradients persisted after adjustment for other environmental variables (odds ratios for ever having had asthma among Canadian-born Chinese compared with native Chinese in Guangzhou: 2.72 [95% confidence interval 1.75–4.23] for boys and 5.50 [95% confidence interval 3.21–9.44] for girls; p < 0.001 for both). Among Chinese adolescents living in Vancouver, the prevalence of ever wheezing increased with duration of residence, from 14.5% among those living in Canada for less than 7 years to 20.9% among those living their entire life in Canada. The same pattern was observed for the prevalence of ever having had asthma, from 7.7% to 15.9%. Interpretation: Asthma symptoms in Chinese adolescents were lowest among residents of mainland China, were greater for those in Hong Kong and those who had immigrated to Canada, and were highest among those born in Canada. These findings suggest that environmental factors and duration of exposure influence asthma prevalence.

Environmental exposures during early life have been suggested to have the greatest impact on childhood asthma. Our aim was to evaluate the risk factors associated with asthma at age 7 yr in a high‐risk cohort that participated in a randomized controlled study on the primary prevention of asthma. Indoor exposures were characterized before birth and at 2 weeks, 4, 8, 12, 18, and 24 months after birth and again at 7 yr. Nasal scrapings for respiratory viruses were done at the same intervals during the first 2 yr. At age 7, the children were assessed by a pediatric allergist and had allergy skin tests. Logistic regression analysis was undertaken to evaluate the effect of exposures on asthma for the entire cohort with adjustment for group allocation. In addition to the lower risk of asthma in the intervention group, we found a higher prevalence of asthma at age 7 for males, those having a positive history of asthma in mother, father, or older siblings, for children residing in Winnipeg and for atopic subjects. Upon adjustment for intervention group assignment and baseline factors, significant environmental risk factors during year 1 included dog ownership and respiratory syncytial viral infection detected at 12 months while maternal smoking was protective. Dog ownership was a significant risk factor in year 2, but highly correlated with dog ownership in year 1. Indoor environmental exposures during year 7 were not associated with asthma at age 7. Maternal smoking at year 7 was associated with a reduced risk of asthma at 7 yr. Early‐life exposures were more important determinants than those in later years. A ‘window of opportunity’ exists for intervention measures to be applied.

The contribution of respiratory viral infections to the onset of asthma and atopy is controversial. In “high risk” children (n = 455) born into asthmatic/atopic families, we determined the relationship of exposures to common respiratory viruses and concomitant respiratory symptoms, and to subsequent possible asthma and atopy at ages 1 and 2 years. Frozen nasal specimens, obtained when children were 2 weeks, 4, 8, and 12 months old, underwent reverse transcription‐polymerase chain reaction (RT‐PCR) testing for parainfluenza virus (PIV), respiratory syncytial virus (RSV), and picornavirus (rhinovirus/enterovirus). Odds ratios of viral RT‐PCR results to respiratory symptoms (“cold,” rhinitis, cough, wheezing) and to possible asthma or atopy at 1 and 2 years of age were calculated. Positive viral RT‐PCR was associated with increased odds of “cold” and cough; PIV and picornavirus were associated with rhinitis, and RSV was associated with wheezing. PIV was associated with increased odds of atopy at 1 year of age in the control group; PIV and RSV were associated with possible asthma at 2 years of age. We conclude that in high‐risk children, viral exposures documented by RT‐PCR are associated with respiratory symptoms, and exposures to PIV and RSV during the first year of life are associated with the initial onset of possible asthma. Pediatr Pulmonol. 2007; 42:290–297.