A Cochrane review [Abstract] 1 [withdrawn from publication] included 18 studies with a total of 369 subjects. A meta-analysis was not possible. There were varied conclusions from the different trials reflecting their heterogeneity. Compared to placebo, short-acting beta-2 agonists increased FEV1 in the short term in three out of five trials, and in the long-term increased peak expiratory flow rate in individuals who had been shown to have bronchial hyperreactivity or bronchodilator responsiveness or both. Compared to placebo, long-acting beta-2 agonists increased FEV1 and forced expiratory flow between 25% and 75% of expiratory flow (FEF 25-75%) in the short term in participants known to have bronchodilator responsiveness, but produced inconsistent results in long-term trials. Short-acting anticholinergics had no consistent effect on lung function tests in either the short or the long term.
Comment: The quality of evidence is downgraded by imprecise results (limited study size for each comparison) and by inconsistency (variability in results across studies).
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