Early life origins of asthma
In order to identify children at risk of developing asthma, we need to better
understand the early natural history of the disease. There is growing evidence
that both genetic and environmental factors have significant effects on airway
development and function in early life and influence both the onset and course
of asthma.24
At-risk children have compromised airways from birth, plus skewed immune
responses and raised IgE levels during the first years of life. A prospective
birth cohort study in the UK found that atopic and non-atopic children who had
never wheezed, but had atopic parents, had lower lung function than children
without a family history of atopy or asthma.6
This suggests that their airways could be pre-modelled, possibly in utero,
putting them at increased risk of developing respiratory diseases such as
asthma.6
The identification of ‘asthma genes’ related to IgE synthesis and allergic
inflammation indicates that a genetic susceptibility to develop asthma is
present from conception. It may be that clinical expression of asthma then
depends on environmental factors2
that operate differently in susceptible individuals, interacting with the
developing immune system to cause disease.18
Recent evidence suggests that environmental factors mediate the onset of
persistent wheezing in genetically predisposed children, so avoiding allergens
and other associated factors may delay but not prevent the onset of childhood
asthma.25
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Is it possible to prevent wheezing and asthma
in a young child with a genetic predisposition?
On current evidence it is still not possible to answer this question. Decades
of research have shed light on many aspects of asthma but because of its
complexity it remains difficult to identify causative factors and develop
interventions to address them. For this to occur, we need to know much more,
including:
-
the environmental factors that interact with ‘asthma genes’
in the development of persistent wheezing and asthma
-
which tools can be used to distinguish young children who
are at high risk of developing asthma from the larger group with
transient wheezing
-
which strategies can prevent deficits in lung function in
very young children in whom the disease process is beginning
-
the nature of the population at risk, so we can develop
interventions that are effective in preventing different types
of childhood asthma
-
the time frame in which to intervene with various
approaches.
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