Summary studies included in review
| Type of study | Publications found in the search and considered in the review |
| Meta-analysis or systematic review | 4 (3 meta-analyses, 1 systematic review) |
| Randomised controlled trial | 53 (765 participants in total of which 682 people with asthma and 83 with reversible airways disease) |
| Non-randomised trial | 31 (106 915 participants in total of which 63 763 were asthma alone, 43 152 were asthma or COPD) |
| Literature review | 12 (9 asthma, 1 obstructive lung disease, 1 reversible airways disease and 1 on adverse reactions to β-blockers) |
| Other | 27 (8 case reports, 7 murine models, 7 guinea pig models, 4 opinion articles, 1 questionnaire) |
Studies that could be allocated to two categories are included in the highest tier (for example, meta-analysis above non-randomised trial).