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.