Study characteristics
| Study type | Country | n | Reference |
|---|---|---|---|
| Randomised control trials (including one randomised control pilot study) | US | 5 | 29, 31, 35, 36, 37 |
| Norway | 3 | 30, 33, 34 | |
| UK | 1 | 32 | |
| Cohort studies (including one retrospective cohort study, one cross-sectional cohort study, one retrospective cohort, and matched-control study) | US | 4 | 38, 39, 40, 41 |
| Cluster randomised control trials | US | 3 | 42, 43, 44 |
| Quasi-experimental trial | US | 1 | 45 |