Introduction
The Australian Paediatric Respiratory Group has recommended a stepwise approach to the treatment of asthma.1 Children with infrequent episodic disease should usually take an inhaled bronchodilator such as salbutamol 'as necessary'. Those with frequent episodic symptoms should receive preventive therapy with regular sodium cromoglycate or nedocromil sodium, together with a bronchodilator as needed for break-through symptoms. Those with persistent asthma, characterised by daily symptoms, should receive regular inhaled corticosteroids together with intermittent bronchodilators as needed.
Other clinicians recommend a different approach to the treatment of asthma, using inhaled corticosteroids as first-line therapy. This approach claims that inhaled corticosteroids should be started at the onset of asthma to prevent untreated airway inflammation leading to permanent lung damage.
Severity of asthma
At one end of the spectrum of asthma are the children (approximately 5% of those with asthma) who have persistent disease. These children have persisting airways obstruction for weeks or months at a time, manifested by cough, wheeze and breathlessness. There is unanimous agreement that these children need regular preventive therapy and that inhaled corticosteroids will be the mainstay of drug management.
About 20% of the population of children with asthma have frequent episodic symptoms. As a guideline, these children will have more than 6-8 attacks of asthma a year and will have symptoms at least every month. Once again, there is no doubt that these children need preventive therapy. Sodium cromoglycate is often very effective in this group, particularly in those with fewer symptoms. It is also almost completely free of adverse effects. Inhaled corticosteroids would also be effective in children with frequent episodic symptoms, but my approach has been to reserve them for the children who fail to respond to sodium cromoglycate or nedocromil. My rationale is that concern about adverse effects, in particular, growth retardation, makes it desirable to limit the use of steroids to those children in whom they are clearly indicated and for whom no safer effective alternative is available. Persistent asthma is associated with growth retardation and the use of steroids in these children may accelerate growth. There is no corresponding argument for children with episodic asthma.
At the mildest end of the spectrum of severity are the 75% of asthmatic children with infrequent episodic asthma. There is no clinical reason for them to be on regular medication, so using a bronchodilator, as necessary, is all they need to enable them to lead normal lives. If the only rationale for the treatment of asthma were the reduction or abolition of symptoms, then inhaled corticosteroids would be prescribed in a minority of children with asthma.
Chronic lung damage
Another possible reason for treating asthma is that, if untreated, asthma results in long-term damage. Airway inflammation has been recognised as one of the features of asthma for over 100 years. The limited data we have show that this inflammation is found in the airways of children with episodic as well as persistent disease. Some workers are concerned that untreated airway inflammation in children sows the seeds for chronic airflow limitation in adults. They believe that the only way to prevent this from occurring is the early introduction of inhaled corticosteroid therapy.
There are a number of flaws to this argument. The first flaw relates to an appreciation of the natural history of untreated disease. There are now a number of studies which have followed young children with asthma throughout childhood and into adult life. For example, a cohort of 7-year-old Melbourne school children with a range of severity of asthma was reviewed at 14, 21, 28 and 35 years of age. The children with infrequent episodic asthma received neither inhaled corticosteroids nor sodium cromoglycate. They can be thought of as a group who show the natural history of untreated infrequent episodic asthma. The prognosis in these children was excellent.2 As adults, they had both a good clinical outcome and normal lung function. In the absence of preventive medication, these children did not go on to develop chronic lung disease as 35-year-old adults. There is no potential for inhaled corticosteroids to improve the excellent prognosis that these children have.
The British National Child Development Study, which is a longitudinal study of all people in England, Scotland and Wales born during a week in March in 1958, shows similar results, namely an excellent prognosis for infrequent wheezing in childhood.3 About half of British people born in 1958 experienced one or more episodes of wheezing illness by 33 years of age. Treating all these people with inhaled corticosteroids would make one think not only that asthma was a disease of inhaled steroid deficiency, but also that life was a disease of inhaled steroid deficiency.
The data on children with frequent episodic asthma and persistent asthma followed into adult life support concerns about persistence of symptoms and the development of abnormal lung function. Even here, although there is intuitive logic that the use of anti-inflammatory medications might have a beneficial long-term effect, the data are not available to be confident that the use of anti-inflammatory therapy does have this effect. Indeed, the limited information that is available from techniques such as induced sputum suggests that airway inflammation persists in those treated with inhaled steroids.
Conclusion
There is no evidence that children with infrequent episodic asthma have an unfavourable long-term outcome if they do not receive anti-inflammatory therapy. Inhaled steroids are not justified for prevention of their minor clinical symptoms during childhood and they are not likely to develop chronic lung disease if they are deprived of steroids.
A further concern about the widespread use of inhaled corticosteroid therapy in young children is that many of these children with recurrent wheeze in the first years of life do not suffer from asthma after the age of 6 years. Approximately one third of children who wheeze in association with lower respiratory tract illnesses in the first 3 years of life are still wheezing by the age of 6, but two thirds are not. Clinically, it is impossible to distinguish between these two groups during the first years of life because their symptoms and signs of illness are very similar. Treating all these children as though they have a long-term problem that will result in lung damage unless steroids are prescribed is incorrect.
Inhaled corticosteroids remain a valuable therapy in children with asthma, especially those who have persistent symptoms. Current evidence does not support an extrapolation of these data to the widespread use of corticosteroids in wheezy children with trivial symptoms in childhood and an excellent lung prognosis into adult life.
