Objective: Systematic reviews (SRs) are convenient summaries of evidence for health care practitioners. They form a basis for clinical practice guidelines and suggest directions for new research. SRs are most helpful if they are current; however, most of them are not being updated. This SR summarizes strategies and methods describing when and how to update SRs.
Study design and setting: We searched MEDLINE (1966 to December 2005), PsycINFO, the Cochrane Methodology Register, and the 2005 Cochrane Colloquium proceedings to identify records describing when and how to update SRs in health care.
Results: Four updating strategies, one technique, and two statistical methods were identified. Three strategies addressed steps for updating, and one strategy presented a model for assessing the need to update. One technique discussed the use of the "entry date" field in bibliographic searching. The statistical methods were cumulative meta-analysis and a test for detecting outdated meta-analyses with statistically nonsignificant results.
Conclusion: Little research has been conducted on when and how to update SRs in contrast to other methodological areas of conducting SRs (e.g., publication bias, variance imputation). The feasibility and efficiency of the identified approaches is uncertain. More research is needed to develop pragmatic and efficient methodologies for updating SRs.