Abstract
Background: The effects of infection and developmental adaptations in infancy on the prevalence of subsequent atopy-related diseases at different ages during childhood are not fully determined. This study aims to examine the similarities and differences in the age-specific association of asthma, allergic rhinitis/conjunctivitis, and atopic dermatitis with early life infection (i.e., daycare, older siblings, and severe airway infection) and developmental adaptations (i.e., preterm birth and overweight gain) in children.
Methods: In this longitudinal cohort study (n = 47,015), children were followed from 0.5 to 11 years. The potential risks and protective factors, including daycare attendance at 0.5 years, existence of older siblings, history of hospitalization due to cold/bronchitis/bronchiolitis/pneumonia during 0.5–1.5 years, preterm birth, and overweight gain at 2.5 years, were assessed using multivariable logistic regression with adjustments for potential confounders.
Results: A negative association was observed between early life daycare attendance and asthma at 5.5–9 years, which disappeared after 10 years. A negative association was also noted throughout childhood between early life daycare attendance and the presence of older siblings with allergic rhinitis/conjunctivitis. However, the association between early daycare and atopic dermatitis was found to be positive during childhood. In contrast, the early life history of hospitalization owing to cold/bronchitis/bronchiolitis/pneumonia was identified to be a risk factor for developing both asthma and allergic rhinitis/conjunctivitis. Preterm birth was a significant risk factor for childhood asthma.
Conclusion: Different age-specific patterns were demonstrated in the relationship between early life daycare, severe airway infection, preterm birth, and atopy-related diseases in childhood.
Key Words: infection, preterm birth, asthma, allergic rhinitis/conjunctivitis, atopic dermatitis
Key Message: The etiology of atopic diseases such as asthma, allergic rhinitis/conjunctivitis, and atopic dermatitis are not fully understood. Research findings reporting the effects of early life risk and protective factors on subsequent atopic diseases are inconsistent. This research revealed the similarities and differences of the age-specific associations of several atopic diseases that share the characteristics of atopic manifestations with early life factors using one cohort. This study could potentially help to modify atopic diseases progression by preventing or delaying early life influences.
Abbreviation: OR, odds ratio
Introduction
Investigating the etiology of atopic diseases such as asthma, allergic rhinitis/conjunctivitis, and atopic dermatitis has remained to be challenge. Reports 1, 2 have indicated that a part of the development of atopic diseases is dictated by the growing organs and immune systems; environmental exposures and host predispositions in early life can modify the development of atopic diseases. However, the findings that have been reported on the effects of early life risk and protective factors on subsequent atopic diseases have been noted to be inconsistent. In this study, we focused on infection and developmental adaptations in infants as the two major influencing factors in the development of diseases related with atopic march.
The effects of infection in early life on atopic diseases, including asthma, are conflicting. The hygiene hypothesis shows that exposure to microbes, through contact with other children or livestock, during immunologic maturation may lower the risk for the subsequent development of atopic diseases. This hypothesis may explain the increase in the prevalence of atopic diseases over the last few decades: a lower opportunity for airway infection and/or exposure to microbes in early life due to the improvement in hygiene and a decrease in family size. However, the relationship between infection and subsequent atopic diseases remains inconsistent. Severe infection, such as hospitalization with bronchiolitis, has been determined as a risk factor for the development of asthma 3.
The relationship between developmental adaptations in infants and subsequent atopic diseases also show inconsistent findings. Recently, it has been shown that the effect of potential factors on asthma, such as overweight gain, may differ at different ages 4-6. The age-dependent pathophysiology involved in the development of atopic diseases could explain the inconsistent relationships. Furthermore, to explore the similarities and differences for asthma, allergic rhinitis/conjunctivitis, and atopic dermatitis could lead to prevent occurrence of each disease by revealing common exposures to the three atopy-related diseases and disease distinct factors. However, there exist no longitudinal studies that have analyzed the age-specific association of the three atopic diseases with the early life factors.
The main aim of this study was to assess the longitudinal phenotype, defined by the association of the three atopy-related diseases with early life factors and their time course, using one large cohort. We have investigated the relationships of the characteristics in early life, including early daycare attendance, existence of older siblings, history of severe airway infection, preterm birth, and overweight gain, with the longitudinal prevalence of atopic diseases in a cohort of children that were followed from birth.