Inhaled corticosteroids in children: use and effects of early treatment on asthma and lung function. Prevalence of asthma and the impact of severity in early life on later asthma in childhood.

INTRODUCTION: The role of inhaled corticosteroids (ICS) on disease progression in asthmatic children is not yet clear.

AIMS: This study was conducted (i) to determine how often ICS were used for treatment of obstructive airways disease (OAD) in early childhood; (ii) to assess if ICS treatment had an effect on lung function in young children with recurrent bronchial obstruction (rBO); (iii) to explore if early ICS treatment in children with OAD during the first 2 years of life can modify occurrence of current asthma in school children; (iv) to define a severity score for severity of OAD during the first 2 years of life and assess if the severity score can be used to predict asthma in school children; and (v) to investigate the prevalence of asthma in children in an urban population.

SUBJECTS AND METHODS: The present study is part of a 10-year follow-up of children in the prospective birth cohort (n = 3754), the Environment and Childhood Asthma study in Oslo. For aim 1, all children from the entire cohort who had completed follow-up questionnaires as well as all children defined with rBO were assessed. For aim 2, 54 children with rBO (with and without ICS treatment) and 15 controls with tidal flow volume measurements upon presentation of the disease and 2 years of age were studied. For aims 3 and 4, 459 subjects (with and without rBO at 2 years of age) from the case control study who attended 10-year follow-up were studied. For aim 5, the 616 of 803 subjects who had lung function measurements performed after birth were reinvestigated at the age of 10 years.

RESULTS: A total of 2.1% of all the children in the cohort and 21% of children with rBO had received ICS treatment by 2 years of age. The mean difference of change in baseline tidal breathing (the ratio of time to peak expiratory flow to total expiratory time) was significantly higher in the ICS-treated group only by 2 years of age and correlated significantly with duration of ICS treatment. However, in rBO children, the use of ICS treatment before 2 years of age was not associated with reduced risk of current asthma at 10 years of age. The risk (odds ratio, 95% confidence interval) of current asthma among rBO subjects with a severity score above five was 20.2, 9.9-41.3 compared to controls. In 10-year-old children, the lifetime prevalence of asthma was 20.2%.

CONCLUSIONS: One-fifth of young children with recurrent bronchial obstruction had received inhaled corticosteroids by age 2 years. Lung function appeared to improve in children using ICS from the start of symptoms of OAD until 2 years of age, mostly in children with the longest duration of treatment. However, use of ICS during the first 2 years of life in children with OAD did not reduce asthma present 8 years later. A scoring system based on severity and frequency of OAD during the first 2 years of life predicted current asthma at 10 years of age. One in five 10-year-old children in the city of Oslo at some time had asthma.