Table 3 Characteristics of eight updated Cochrane Methodology Reviews

Authorship of updated review

 Identical to original review [21, 24]

2 (25.0%)

 Different authors and different order [26, 28, 33]

3 (37.5%)

 Authors added or removed [22, 23, 25]

3 (37.5%)

Number of updates

 One [21,22,23,24,25]

5 (62.5%)

 Three [26, 28, 33]

3 (37.5%)

Interval between original and updated review

 One year [21]

1 (12.5%)

 Two years [24]

1 (12.5%)

 Three years [28, 33]

2 (25.0%)

 Four years [25]

1 (12.5%)

 Five years [23]

1 (12.5%)

 Eleven years [22, 26]

2 (25.0%)

Methodological topic of included studies

 Randomization method [25, 26, 28, 33]

4 (50.0%)

 Conflict of interest [23]

1 (12.5%)

 Technical editing [21]

1 (12.5%)

 Full publication of results [22]

1 (12.5%)

  Questionnaires [24]

1 (12.5%)

Conclusions

 Same as previous version [21,22,23,24,25]

5 (62.5%)

 Different to previous version [26, 28, 33]

3 (37.5%)