Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
COPD exacerbation
[48] Systematic review	1460 people 2 RCTs in this analysis	Proportion of people with an exacerbation of COPD 159/730 (22%) with tiotropium 178/730 (24%) with salmeterol	OR 0.86 95% CI 0.67 to 1.11 P = 0.24		Not significant