Objectives: To compare the number and size of clinical trials included in chronic asthma/COPD reviews with acute asthma/COPD reviews published in the Cochrane Library.
Methods: Accessed the Cochrane reviews on line. Statistics: simple descriptive and comparisons.
Results: A total of 29 acute and 91 chronic SRs were identified. The average number of participants per review in acute reviews was 574 compared with 2072 in chronic reviews (p = 0.02). The average number of included studies in acute respiratory reviews was 10 compared with 14.2 in chronic respiratory reviews (p = 0.07).
Conclusions: Although there was a non-significant difference in the number of studies included in acute and chronic respiratory reviews, studies included in chronic respiratory Cochrane reviews were larger. Small trials are associated with providing less accurate effect estimates, and may be prone to chance findings. More research using larger samples is required to answer important clinical questions for clinicians, consumers and policy makers in the treatment of acute respiratory diseases.