Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Lung function
[52] RCT 4-armed trial	854 people	Mean difference in FEV1 12 months with theophylline (220 mg or 300 mg slow-release formulation) with placebo Absolute results not reported	Difference between groups: +120 mL (theophylline v placebo) CI not reported P <0.001 The theophylline arm was open label	Effect size not calculated	theophylline
[53] RCT	110 people	Mean change in pre-bronchodilator FEV1 (change from baseline) 12 months +6.3 mL with theophylline (100 mg twice daily) –53.3 mL with placebo	P = 0.04	Effect size not calculated	theophylline
[53] RCT	110 people	Mean change in post-bronchodilator FEV1 (change from baseline) 12 months –55.9 mL with theophylline (100 mg twice daily) –55.7 mL with placebo	P = 0.50		Not significant