PURPOSE OF THE STUDY.
The goal of this study was to identify better ways to characterize microbial exposure early in life as a possible predictor of respiratory symptoms and allergies.
A birth cohort of 410 children in Finland was recruited over a 3-year period and followed up until 6 years of age.
Asthma, wheezing, cough, and atopic dermatitis were assessed by questionnaires administered during the third trimester and in follow-up at ages 2, 12, 18, and 24 months and yearly thereafter. Dust samples were collected at 2 months of age and analyzed for bacterial endotoxin, 3-hydroxy fatty acids, N-acetyl-muramic acid, fungal extracellular polysaccharides, β-D-glucan, ergosterol, and bacterial or fungal quantitative polymerase chain reaction (qPCR). Specific immunoglobulin E levels to aeroallergens were determined at ages 1 and 6 years.
Development of asthma and allergic sensitization were examined, and only a few associations were found with single microbial markers. In contrast, a score for the total quantity of microbial exposure (bacteria and fungi) was significantly associated with asthma incidence (P < .001); the highest risk was found at medium levels (middle portion of an inverted U-shape curve) and the lowest risk was found at the highest level. The microbial diversity score (sum of detected qPCRs) was inversely associated with risk of wheezing and was significantly associated with sensitization to inhalant allergens at age 6 years, but not with atopic dermatitis.
This study illustrates that the score for total quantity of microbial exposure predicted asthma better than single microbial markers independently of microbial diversity and amount of dust.
Several factors are involved in the relationship between microbial exposure and the development of asthma and allergic sensitization that have been examined in other studies. These include timing relative to age of the subject, amount, duration, and diversity. This study used a unique index of a total microbial quantity score in addition to qPCR assessments of microbial diversity. Further studies with large cohorts in different settings as well as more accurate exposure assessment data will add to the knowledge base that can help better predict risk for the development of asthma and allergies.
- Copyright © 2015 by the American Academy of Pediatrics