Wheezing in childhood
Wheezing is a non-specific symptom that results from obstruction of the lower
airways. In westernised countries, wheezing affects about one-third of babies in
their first year.1
Wheezing-associated respiratory illnesses in children are often described as
asthma.4
But while most children with asthma wheeze, not all wheezing is related to
asthma. Wheezing in infancy and childhood is not a single disorder4
and is just as likely to be due to causes other than asthma.5
Understanding the different wheezing disorders may help to identify young
children whose wheezing is likely to be related to development of asthma5
and to avoid inappropriate treatment of children with non-asthma related wheeze.6
During this process it is important to remember that:
- evaluating wheezing is part of the overall process of diagnosing asthma
and other respiratory conditions, and it remains difficult to distinguish
young children with atopic asthma from the larger group with wheezing;7
and
- minor respiratory illnesses are common in childhood and are needed to
build up a child’s immunity. They generally do not require medical treatment
and in many cases are not an indication that a child will develop asthma.8
Wheeze unlikely to be related to asthma
More than half of the children who wheeze during their first three years
have:1
- congenital or acquired structural abnormalities that reduce the size of
the airways;
- cystic fibrosis causing excess production of thick mucus in the airways;
- bronchiolitis not requiring hospitalisation; or
- viral-induced transient early wheezing.
Specific conditions such as structural abnormalities and cystic fibrosis that
lead to lower airway obstruction and wheezing can generally be identified.1
Bronchiolitis that causes wheezing in the first years of life is usually
associated with reduced rates of airflow that will continue into later childhood
but does not increase the risk of asthma.1
Transient early wheezing is caused by transient conditions (generally lower
respiratory infections) associated with small airway calibre in infancy. In this
group of children, lower respiratory illness is not associated with allergy, and
the wheezing and other respiratory symptoms tend to resolve as the child grows
and the airways widen,7 usually by the
age of three.5
Transient wheezing does not increase the risk of asthma or allergy later in
life.5
Wheeze likely to be related to asthma
Persistent wheezing is wheezing that continues and may develop into asthma.5
This is more likely if there are other risk factors such as a family history of
asthma or atopy1
(see factors associated with wheezing below). Bronchiolitis or wheezy bronchitis
requiring hospitalisation is also likely to be related to later onset of asthma.1,9
Persistent wheezing may have an early or late onset:5
- early onset – children who begin wheezing during their first three years
and continue to wheeze up to school age.4,5
- late onset – children who do not wheeze in the first three years of life
but begin wheezing around the age of six years.4,5
Regardless of when symptoms occur, children with persistent wheezing are more
likely to have developed atopy than children with transient early wheezing.4
They already have raised serum IgE levels and diminished airway function within
their first year and have reduced lung function by the age of six.5
The reduced lung function seen in young adults with asthma can be traced back
to the impact that the disease process has on the growth and maturation of the
lungs and airways in the first six years of life.10,11
There appears to be little further change in lung function after this age.12
The lungs grow more rapidly during this time than at any other, allowing the
disease process to have its greatest impact.12,13
The earlier asthma symptoms appear, the more severe the disease in later
life and the greater the damage to the airways.14
