Inhaled corticosteroids in asthma and longitudinal change in lung function: a systematic review and meta-analysis

Abstract

Background: Asthma is associated with accelerated lung function decline and increased risk of fixed airflow obstruction. It remains unclear whether inhaled corticosteroids modify these long-term risks. Objective: To investigate the long-term effects of ICS on lung function in children and adults with current asthma. Methods: Systematic searches were performed of the PUBMED, EMBASE and CENTRAL databases. Randomised controlled trials (RCT) and observational studies with a follow-up of one year or greater were included. Results: 22 studies met the pre-specified inclusion criteria, including 12 RCT (n=11,427) and 10 observational studies (n=3,698). Median follow-up was 1.4 (range: 1-4) and 8.4 (3-28) years for RCT and observational studies, respectively. Within the experimental trials, predominately in individuals with mild asthma, ICS treatment favourably influenced pre-bronchodilator (BD) lung function (FEV1) (+2.24% predicted (95%CI 1.33, 3.14)) compared to placebo, with similar estimates of strength in association for children and adults. Improved post-BD lung function (FEV1) was observed in adults in one study (+1.54% (0.87, 2.21), N=3,970), but not in children from three studies (+0.42 (-0.42, 1.25); N=3,195) (p-interaction=0.04). The greatest benefits on lung function were obtained during the first year of treatment. No differences were observed by smoking status. Within the observational studies, ICS treatment was only associated with improved pre-BD lung function (FEV1) in children (+1.40% per-year (0.73,2.08)). Conclusion: ICS treatment is associated with modest improvements in long-term lung function, but there is evidence this effect is modified by age.