PURPOSE OF THE STUDY.
The HITEA (Health Effects of Indoor Pollutants: Integrating microbial, Toxicological and Epidemiological Approaches) project is focused on evaluating the impact of indoor exposures on the development of asthma and atopy in children from existing population cohorts.
The study included 1429 children from 3 European birth cohorts that were initiated between 1996 and 1999: subsamples from the PIAMA (Prevention and Incidence of Asthma and Mite Allergy, n = 553) cohort from the Netherlands, INMA-Menorca (Infancia y Medio Ambiente—Childhood and Environment, n = 481) cohort from Spain, and the LISAplus (Influence of Life-style factors on the development of the Immune System and Allergies in East and West Germany, n = 395) cohort from Germany.
Detailed information of how each of the cohorts were recruited, and how exposure data were obtained is described elsewhere (Casas et al. Indoor Air. 2013;23(3):208–218). The PIAMA cohort was recruited during second trimester in 1996–1997. Living room floor dust samples were taken at 2 to 3 months in the intervention arm (children of allergic and/or asthmatic mothers). The INMA-Menorca cohort was recruited during the third trimester in 1997–1999. Living room sofa dust samples were taken at the age of 2 to 3 months. The LISAplus cohort was recruited as neonates in 1997–1999. Random sampling of participant’s dust samples were used in analysis. Living room floor dust samples were taken at 2 to 3 months. Longitudinal questionnaires were performed in all cohorts where asthma was assessed at 6 and 10 years of age. Specific immunoglobulin E to common aeroallergens were assessed at ages 8 and 10 years in the PIAMA and LISAplus cohorts.
Current asthma at 6 and 10 years and ever being diagnosed with asthma at 10 years was most prevalent in the PIAMA cohort at 7%, 6%, and 16% versus INMA and LISAplus cohorts at 3%, 4%, and 6%, respectively. Aeroallergen sensitization was more prevalent in the PIAMA cohort at 8 years (39%) versus the LISAplus cohort at 10 years (22%). Endotoxin concentration was significantly associated with current asthma at 6 years in PIAMA (odds ratio 1.96, 95% confidence interval 1.07–3.58). Endotoxin load was significantly protective for doctor-diagnosed asthma ever at 10 years of age in INMA (odds ratio 0.39, 95% confidence interval 0.16–0.94). There was no significant association between endotoxin and asthma in LISAplus. There was no significant association between (1,3)-β-D-glucan concentrations and asthma and aeroallergen sensitization in PIAMA and LISA plus. There was no significant association between fungal extracellular polysaccharide concentrations or loads, and asthma outcomes and aeroallergen sensitization in all 3 cohorts.
In the PIAMA cohort endotoxin concentrations at 2 to 3 months of age were associated with a 1.96 increased odds of current asthma at 6 years of age. In the INMA cohort, endotoxin loads at 2 to 3 months of age were associated with 0.39 decreased odds of doctor-diagnosed asthma ever at 10 years of age.
This study was unique in its attempt examine the impact of bio-contaminant exposure in infancy with asthma outcomes in later childhood in children living in diverse suburban environments. However it has inconsistent results where in 1 cohort endotoxin was associated with increased odds of current asthma at 6 years of age, whereas in another cohort, it was associated with decreased odds of doctor-diagnosed asthma ever at 10 years of age. This inconsistency could be related to several factors. The PIAMA cohort dust samples were taken only from children of atopic mothers. In addition, the dust samples were only collected at 1 time-point in infancy, although it is acknowledged that resources can limit how often samples can be ascertained. Variations in timing and dose of exposure can account for these differences, but the concept of combining data from multiple cohorts is desirable.
- Copyright © 2015 by the American Academy of Pediatrics