| Study | Reason for exclusion |
|---|---|
| AACN 2012 | Commentary paper on Jones 2012 |
| Backman 2001 | Observational study |
| Backman 2010 | Prospective cohort study with retrospective reference group |
| Bagger 2006 | Observational study |
| Garrouste‐Orgeas 2012 | Time‐series design |
| Hale 2010 | Observational study |
| Hayes 2008 | Observational study |
| MacDonald 2011 | Observational study |
| Robson 2008 | Observational study |
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