Use and application of geographical restrictions in systematic reviews with the aim of including studies about Germany: An update of a methodological review

Background: In systematic reviews (SRs), geographical limitations in literature searches can aid in focussing research efforts. A methodological review published in 2016 examined the approaches SR authors use to identify studies about Germany, analysing 36 SRs.

Objective: The aim of this study was to update the original review.

Methods: We conducted a literature search on PubMed for SRs synthesising evidence from studies about Germany published between 22 January 2016 and 7 June 2022. Two reviewers independently performed study selection and data extraction. We evaluated the application of search syntax for restricting studies to those about Germany using the peer review of electronic search strategies criteria. The updated findings were reported and summarised alongside those of the original review.

Results: Thirty-two additional SRs were newly included (total = 68). Geographic restrictions were applied in 57 SRs, representing 72% in the original review and increasing to 97% in the newly included SRs. Moreover, there was an increased use of truncations and field tags.

Conclusion: Although geographical restriction methods are increasingly utilised, additional tools are necessary to enhance the robustness of search strategies. The development of a dedicated geographical search filter would facilitate the identification of studies about Germany.