Study	Reason for exclusion
Chapman 2002a	Examined whether or not conclusions of Cochrane reviews as well as surgical reviews changed after they were updated. No updating methods were described.
Counsell 1994	Examined whether systematic reviews can be routinely updated. No updating methods were described.
Eccles 2002	Described how two clinical guidelines were updated. No updating method for systematic reviews was described.
Enkin 1996	Described the authors' efforts to identify all literature for one of their systematic reviews. No updating methods were described.
French 2004	Found that updating Cochrane reviews may be a resource‐intensive process, because it does not always result in a change of the conclusion. No updating methods were described.
McCormack 2004	Discussed an important issue in updating a systematic review in surgery, yet it did not describe any updating methods.
Mowatt 1998	Reviewed issues related to timing of health technology assessment. No method for updating systematic reviews was discussed.
Orwin 1983	Described the use of the "fail safe N" for detecting publication bias. We excluded methodological articles on publication bias, as they have been described elsewhere.
Stead 2001a	Examined how updating influenced the results of systematic reviews in nicotine replacement therapy. No updating method for systematic reviews was reported.
Urquhart 1996	Described methodological issues related to the value of information analysis. The authors did not address issues of updating systematic reviews.
van Tulder 2003	Appraised all reviews published by the Cochrane Back Review Group according to the Cochrane guidelines. No updating methods were described.