Updating reviews when new studies are found

If new, potentially relevant, studies are found, they need to be assessed for inclusion in the review using the same process (and study selection form) as the original review (for information about study selection, see Chapter 5).


If new studies are to be included in the updated review, citations should be entered into RevMan, data collected (see Chapter 7), and risk of bias assessed (see Chapter 8). Data collected from the newly identified and included studies should be entered into RevMan and, if sensible, a (new) meta-analysis performed (Chapter 9). Where possible the methods employed in the review update should mimic those of the original review, unless explicitly altered (for example through developments in systematic review methods such as use of ‘Risk of bias’ tables or inclusion of ‘Summary of findings’ tables). In cases where methods differ from those of the original review, these differences and their justification should be documented in the ‘Differences between review and protocol’ section of the review.


The amount of revision required to the text of an updated review including new studies will depend on the influence of the new data on the results of the review. Examples range from the addition of small studies bringing about no change in the results or conclusions of the review (and so requiring very little revision of the text beyond that described in Section through to increased certainty of pre-existing results and conclusions (requiring some modification of the text) and, in some cases, a change in the conclusion of a review (with the subsequent need for a major rewrite of the Results, Discussion, Conclusion, ‘Summary of findings’ table, Abstract and 'Plain language summary'). In addition, the statements in the Abstract and Background sections of the review alerting readers to the fact that this is an update of an earlier review (see Section should be included.


Authors will need to ensure that the relevant date fields are correct and reflect the updated status of the review (see Section 3.3.2), and the ‘What’s new’ table is completed (see Section 3.5). Finally, authors should check that nothing else in the review is out of date (e.g. references to other Cochrane reviews which may have been updated, information about prevalence or incidence of the condition of interest, statements like ‘recently, in 1998, it was shown that …’, ‘next year, in 2002, there will be …’).  If there are changes or additions to the Acknowledgements and 'Declarations of interest' sections of the review these should be revised.