| Year of publication |
Trials included in meta‐analyses |
| 1946 to 1949 | 0 |
| 1950 to 1959 | 0 |
| 1960 to 1969 | 0 |
| 1970 to 1979 | 2 |
| 1980 to 1989 | 13 |
| 1990 to 1999 | 34 |
| 2000 to 2009 | 11 |
| 2010 to 2012 | 0 |
| Overall | 60 trials |
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