Eleven prospective double-blind placebo-controlled RCTs (n=8,164) were included in the review. Follow-up ranged from one to four and a half years. The Jadad score was greater than 3 for all studies, which indicated they were of high quality.
Inhaled corticosteroids were associated with a statistically significant 18% risk reduction in the occurrence of exacerbations (RR 0.82, 95% CI 0.73 to 0.92) over a mean follow-up period of 2.1 years. There was significant heterogeneity in the overall risk of exacerbations (I2=was 55%, 95% CI 0 to 75.6).
Sensitivity analysis that excluded trials of patients with mild to moderate COPD indicated that the reduction in risk of exacerbations was based mainly on those trials with participants who had severe to very severe COPD (FEV1<50% predicted) (RR 0.79, 95% CI 0.69 to 0.89). Heterogeneity in the subgroup of patients with severe COPD was substantial (I2=57.4%).
Metaregression indicated no linear response of FEV1 on exacerbations reduction by inhaled corticosteroids (coefficient 0.006, standard error 0.008, p=0.36).
There was no evidence of publication bias on any test.