| Database | Number of Hits |
| Medline (Ovid): | 495 |
| Embase (Ovid): | 557 |
| The Cochrane Library: | 0 |
| Cochrane Central Register of Controlled Trials: | 79 |
| Number of references before removal of duplicates: | 1131 |
| Number of referencesafter removal of duplicates: | 694 |
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