• Top
• Objective
• Method
• Results
• Discussion

Objective

To compare the frequency with which systematic reviews published as Cochrane Reviews are updated compared with those published in paper format.

Method

A cohort of systematic reviews published in 1995 was established comprising (a) all 65 Cochrane Reviews on the Cochrane Datatabase of Systematic Reviews 1995, Issue 2 and (b) 47 systematic reviews published in paper journals in the same year randomly selected from the DARE database. To identify whether a more recent version of the review existed, all databases on the Cochrane Library (Issue 3, 2000) were examined. Where a more recent version of the review was identified, it was noted whether this was as a Cochrane review or paper review. The date of the most recent review and most recent search for new trials were also noted. In addition, the number of updated versions of the review since the original was also noted, as was any change in the authorship of the updated reviews.

Results

A more reecent version of the original review was found for 95% (n=62) of Cochrane reviews but only 69% (n=31) of reviews published in paper journals (OR for a more recent review 9.3 95% CI: 2.5, 34.9). For 59 of the updated Cochrane reviews, the updated version was the most recent version of the review available. Of the 31 updated reviews from paper journals, the most recent version of the review in 42% (n=13) was as a Cochrane review. Cochrane reviews were significantly more likely to be updated by the same or similar group of authors compared with updates of reviews originally paper journals (OR 75.4, 95% CI: 18.7, 303.9). There was also a trend towards the most recent update of a Cochrane review being within the last two years, compared with updates of reviews originally published in paper journals where the most recent review may have been as much as four or five years ago.

Discussion

This study demonstrates that reviews published in the Cochrane Library are more likely to be updated (as well as more recently) than reviews published in paper journals. Whilst this is largely reassuring given the requirement of the Cochrane Collaboration for reviews to be updated on a regular basis, it highlights the benefits of publishing systematic reviews within a framework where updating is regarded as a core part of the process. It is of interest to note the number of reviews originally published in paper journals that are now being maintained as Cochrane Reviews. The question as to whether the reviews that have not been updated are now out-of-date because of new evidence or other reasons remains unanswered.

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