Empty Reviews: A Description and Consideration of Cochrane Systematic Reviews with No Included Studies

Abstract

BackgroundThere is no specific guidance for the reporting of Cochrane systematic reviews that do not have studies eligible for inclusion. As a result, the reporting of these so-called “empty reviews” may vary across reviews. This research explores the incidence of empty systematic reviews in The Cochrane Database of Systematic Reviews (The CDSR) and describes their current characteristics.Methodology/Principal FindingsEmpty reviews within The CDSR as of 15 August 2010 were identified, extracted, and coded for analysis. Review group, original publication year, and time since last update, as well as number of studies listed as excluded, awaiting assessment, or on-going within empty reviews were examined. 376 (8.7%) active reviews in The CDSR reported no included studies. At the time of data collection, 45 (84.9%) of the Cochrane Collaboration's 53 Review Groups sustained at least one empty review, with the number of empty reviews for each of these 45 groups ranging from 1 to 35 (2.2–26.9%). Time since original publication of empty reviews ranged from 0 to 15 years with a mean of 4.2 years (SD = 3.4). Time since last assessed as up-to-date ranged from 0 to 12 years with a mean of 2.8 years (SD = 2.2). The number of excluded studies reported in these reviews ranged from 0 to 124, with an average of 9.6 per review (SD = 14.5). Eighty-eight (23.4%) empty reviews reported no excluded studies, studies awaiting assessment, or on-going studies.ConclusionsThere is a substantial number of empty reviews in The CDSR, and there is some variation in the reporting and updating of empty reviews across Cochrane Review Groups. This variation warrants further analysis, and may indicate a need to develop guidance for the reporting of empty systematic reviews in The CDSR.

The Role of the Amygdala in Facial Trustworthiness Processing: A Systematic Review and Meta-Analyses of fMRI Studies

“…although meta-analysis with only 3 articles [80] are not rare. In this respect, Yaffe et al [81] have made a consideration regarding empty reviews [81, 82] as they usually (1) offer no conclusions, (2) offer conclusions based on referenced excluded studies, (3) offer conclusions based on other evidence, or (4) offer conclusions not based on evidence [81]. These reviews are still informative in the sense they detail reasons for exclusion adding cues regarding lack of data or possible flaws in the research field.…”

“…These reviews are still informative in the sense they detail reasons for exclusion adding cues regarding lack of data or possible flaws in the research field. Reasons for empty reviews, which mimic reasons for few studies reviews, are (a) very recent areas of studies; (b) ask research questions which are very specific; or (c) the inclusion criteria are methodologically very demanding in the sake of quality evidence [81]. As far as we know, the amygdala role in social cognition, and in trustworthiness processing, is largely addressed in the literature (a search in PubMed using “amygdala AND trustworth*” returned 40 articles, whereas using “amygdala AND (social cognition)” returned 505) and the questions posed in this systematic review are addressed by at least 20 articles.…”

Resilience in Chronic Obstructive Pulmonary Disease and Chronic Heart Failure

“…An overview of the manuscript selection, review process and reasons for excluding studies from this review is detailed in Figure 1. Yaffe et al [30] describe this outcome as an empty review which demonstrates limited research has been undertaken on the topic.…”

Commentary on: Predatory publishing; pressures, promotions and perils

“…An analysis of Cochrane reviews in 2010 noted 376 active reviews with no studies included. 4 Quek and Teo also note the exorbitant cost associated with publishing in predatory journals. 1 However, this is presented as though it is something very different from the traditional academic publishing sector.…”