The prevalence of paediatric allergic diseases has recently increased in
developed countries. Adoption of Western lifestyle was noted as a
contributing factor, but it has not been sufficiently
verified.1,2 Western lifestyle is characterised by an
increase in the time spent indoors, highly insulated airtight houses,
and a more hygienic environment; in addition, it may also be
characterised by changes in the pattern of exposure to house dust mite
allergen and microorganisms that influence the prevalence of paediatric
allergic diseases.2There is sufficient scientific evidence for dust mite allergen as a
factor aggravating asthma symptoms, but there is no evidence that it is
a risk factor for asthma incidence.3,4 A European
large-scale birth cohort study showed that exposure to a high
concentration of allergens immediately after birth influences the
development of allergic sensitisation.5,6 Moreover,
exposure to dust mite allergens is associated with dust mite
sensitisation.7 However, intervention studies reported
no associations between dust mite exposure in infancy and asthma onset
at 3 8 or 8 years of age.9Reports suggest no consistency in the association between endotoxin, a
cell wall component of gram-negative rods and microorganism exposure
marker, and asthma development. Braun-Fahrländer et al. reported that in
farming areas in Germany, Austria, and Switzerland, the endotoxin
concentration in bed dust was higher in children of farmers than in that
of other children, and significantly fewer children of farmers had
pollinosis, asthma, and atopic sensitisation.10,11Mendy et al. reported a positive correlation between the endotoxin
concentration in dust (endotoxin concentration per gram of dust) and
wheezing in infants and toddlers (0-3 years old) but an inverse
correlation with asthma after they reached school
age.12Furthermore, recent studies in adult Americans revealed that the
influence on allergic disease differs due to climate and lifestyle
because of differences in exposure to endotoxin and indoor allergens
such as mites and moulds.13,14 Therefore, it is
necessary to clarify the association of exposure to dust mite allergen
and endotoxin with asthma development in Asian regions under different
climatic regions and lifestyles in comparison with that in Western
countries. Although large-scale birth cohort studies have been conducted
in Western countries, there are few reports from Asia, including Japan.
We conducted a large-scale birth cohort study on the effects of
early-life exposure to dust mite allergen and endotoxin in mattresses on
asthma and wheezing development by 0-36 months old in Japan.