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Characteristics of the 23 studies included in the primary analysis
| Description | No of studies (%) |
|---|---|
| Continent of study | |
| North America | 12 (52.2) |
| Europe | 6 (26.1) |
| Asia | 4 (17.4) |
| Australia | 1 (4.3) |
| Year of publication | |
| 1990–94 | 2 (8.7) |
| 1995–99 | 2 (8.7) |
| 2000–04 | 5 (21.7) |
| 2005–09 | 2 (8.7) |
| 2010–14 | 6 (26.1) |
| 2015–19 | 6 (26.1) |
| Study design | |
| Prospective cohort | 10 (43.5) |
| Retrospective cohort | 13 (56.5) |
| Sites | |
| Single centre | 10 (43.5) |
| Multicentre | 13 (56.5) |
