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Bibliometric Study of 'Overviews of Systematic Reviews' of Health Interventions: Evaluation of Prevalence, Citation and Journal Impact Factor

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Title: Bibliometric Study of 'Overviews of Systematic Reviews' of Health Interventions: Evaluation of Prevalence, Citation and Journal Impact Factor
Language: English
Authors: Lunny, Carole (ORCID 0000-0002-7825-6765), Neelakant, Trish, Chen, Alyssa, Shinger, Gavindeep, Stevens, Adrienne (ORCID 0000-0002-6257-4806), Tasnim, Sara, Sadeghipouya, Shadi, Adams, Stephen, Zheng, Yi Wen, Lin, Lester, Yang, Pei Hsuan, Dosanjh, Manpreet, Ngsee, Peter, Ellis, Ursula (ORCID 0000-0002-5896-4852), Shea, Beverley J. (ORCID 0000-0002-7686-2585), Reid, Emma K., Wright, James M.
Source: Research Synthesis Methods. Jan 2022 13(1):109-120.
Availability: Wiley. Available from: John Wiley & Sons, Inc. 111 River Street, Hoboken, NJ 07030. Tel: 800-835-6770; e-mail: cs-journals@wiley.com; Web site: https://www.wiley.com/en-us
Peer Reviewed: Y
Page Count: 12
Publication Date: 2022
Document Type: Journal Articles
Information Analyses
Descriptors: Bibliometrics, Citation Analysis, Journal Articles, Periodicals, Medicine, Literature Reviews, Meta Analysis, Predictor Variables, Incidence, Sample Size, Access to Information, Open Educational Resources
DOI: 10.1002/jrsm.1530
ISSN: 1759-2879
Abstract: Overviews synthesising the results of multiple systematic reviews help inform evidence-based clinical practice. In this first of two companion papers, we evaluate the bibliometrics of overviews, including their prevalence and factors affecting citation rates and journal impact factor (JIF). We searched MEDLINE, Epistemonikos and Cochrane Database of Systematic Reviews (CDSR). We included overviews that: (1) synthesised reviews; (2) conducted a systematic search; (3) had a methods section; and (4) examined a healthcare intervention. Multivariable regression was conducted to determine the association between citation density, JIF and six predictor variables. We found 1218 overviews published from 2000 to 2020; the majority (73%) were published in the most recent 5-year period. We extracted a selection of these overviews (n = 541; 44%) dated from 2000 to 2018. The 541 overviews were published in 307 journals; "CDSR" (8%), "PLOS ONE" (3%) and "Sao Paulo Medical Journal" (2%) were the most prevalent. The majority (70%) were published in journals with impact factors between 0.05 and 3.97. We found a mean citation count of 10 overviews per year, published in journals with a mean JIF of 4.4. In multivariable analysis, overviews with a high number of citations and JIFs had more authors, larger sample sizes, were open access and reported the funding source. An eightfold increase in the number of overviews was found between 2009 and 2020. We identified 332 overviews published in 2020, which is equivalent to one overview published per day. Overviews perform above average for the journals in which they publish.
Abstractor: As Provided
Notes: https://osf.io/38bkg
Entry Date: 2022
Accession Number: EJ1323669
Database: ERIC
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  Value: <anid>AN0154579800;[bdct]01jan.22;2022Jan12.02:26;v2.2.500</anid> <title id="AN0154579800-1">Bibliometric study of 'overviews of systematic reviews' of health interventions: Evaluation of prevalence, citation and journal impact factor </title> <p>Overviews synthesising the results of multiple systematic reviews help inform evidence‐based clinical practice. In this first of two companion papers, we evaluate the bibliometrics of overviews, including their prevalence and factors affecting citation rates and journal impact factor (JIF). We searched MEDLINE, Epistemonikos and Cochrane Database of Systematic Reviews (CDSR). We included overviews that: (a) synthesised reviews, (b) conducted a systematic search, (c) had a methods section and (d) examined a healthcare intervention. Multivariable regression was conducted to determine the association between citation density, JIF and six predictor variables. We found 1218 overviews published from 2000 to 2020; the majority (73%) were published in the most recent 5‐year period. We extracted a selection of these overviews (n = 541; 44%) dated from 2000 to 2018. The 541 overviews were published in 307 journals; CDSR (8%), PLOS ONE (3%) and Sao Paulo Medical Journal (2%) were the most prevalent. The majority (70%) were published in journals with impact factors between 0.05 and 3.97. We found a mean citation count of 10 overviews per year, published in journals with a mean JIF of 4.4. In multivariable analysis, overviews with a high number of citations and JIFs had more authors, larger sample sizes, were open access and reported the funding source. An eightfold increase in the number of overviews was found between 2009 and 2020. We identified 332 overviews published in 2020, which is equivalent to one overview published per day. Overviews perform above average for the journals in which they publish.</p> <p>Keywords: reviews of reviews; bibliometric; citation analysis; epidemiological characteristics; impact factor; meta‐reviews; overview of systematic reviews; overviews of reviews; systematic reviews of systematic reviews; umbrella reviews</p> <hd id="AN0154579800-2">Highlights</hd> <p></p> <ulist> <item> Overviews synthesise the results of multiple systematic reviews.</item> <p></p> <item> Many academics, practitioners and policy makers have failed to see the impact and utility of overviews, and their potential to inform clinical practice, policy and guideline development.</item> <p></p> <item> Citation analysis and journal impact factor (JIF) metrics can quantify, compare and communicate the influence of overviews of reviews.</item> <p></p> <item> Our study reports the results of an empirical study investigating the prevalence, characteristics, number of citations of 'overviews of reviews' indexed in MEDLINE, Epistemonikos and the Cochrane Database of Systematic Reviews.</item> <p></p> <item> Our study findings show the growing prevalence of overviews, and an eightfold increase in the number of overviews published from 2009 to 2020, representing one published overview a day.</item> <p></p> <item> We found a high mean citation count of 10 overviews per year, published in journals with a mean JIF of 4.4. These data indicate that, overall, overviews perform above average for the journals in which they publish.</item> </ulist> <hd id="AN0154579800-3">BACKGROUND</hd> <p>Bibliometric analysis measures the impact of articles using metrics such as the journal impact factor (JIF) and number of citations.1 A bibliometric analysis can serve to identify influential articles that have shaped medical practice, policy decisions and presented new research ideas.2 Citation analysis provides an objective measurement of how often scientists use specific published work. Although citations have limitations,3 they may offer vital information on how often scientific data are used and referenced, and provide one source of information to help prioritise research investment.2</p> <p>Several investigations have found that evidence syntheses, such as systematic reviews with meta‐analysis, received a higher citation rate compared to other study designs4–8; but typically represented only 4–6% of research output.8,9 It is unclear whether 'overviews of systematic reviews' (henceforth called overviews) are cited equally as highly as systematic reviews, but it stands to reason that they might considering they are a type of evidence synthesis.</p> <p>The number of systematic reviews has reached epidemic proportions10; from none in 198711; 7 per day in 20035; 11 a day in 201012; and 22 per day in 2014.13 Overviews have grown in number in tandem with the growth in systematic reviews, and they aim to appraise and synthesise results of systematic reviews. One investigation found a five‐fold increase in the publication of overviews from 2004 to 2011.14 The current number of overviews, and whether the trend in annual publication rate is increasing is unknown.</p> <p>To advance the development of overviews, research is required to understand epidemiological aspects such as annual prevalence and factors that may influence the citation of overview publications. This paper is the first of two companion papers. In this first paper, we present our evaluation of the bibliometric characteristics of overviews, and evaluate factors affecting citation rates and JIF. In a second paper, we will present the assessment of whether two or more overviews overlapped in topic.</p> <hd id="AN0154579800-4">METHODS</hd> <p></p> <hd id="AN0154579800-5">Study design</hd> <p>The design is a bibliometrics study in the knowledge synthesis field. We followed systematic review methods guidance for searching, study selection and data extraction.</p> <hd id="AN0154579800-6">Eligibility criteria</hd> <p>We included overviews published in any language and reports were translated by one of the authors (French, Spanish, German, Mandarin), where needed. We used Google Translate to translate articles in languages other than the ones listed, and when authors were not native speakers of French, Spanish, German or Mandarin. We restricted our search to reports published from January 1, 2000 to December 2020. Given that the Cochrane Handbook for Systematic Reviews of Interventions15 chapter on overviews was first published in 2009, we did not expect to identify overviews published prior to 2000.</p> <p>We reasoned that overviews may exist as stand‐alone reports or also packaged as part of a clinical practice guideline and health technology assessment; accordingly, we developed eligibility criteria for both circumstances.</p> <p> <emph>Inclusion criteria for overviews</emph>:</p> <p></p> <ulist> <item> Aims to primarily focus on synthesising systematic reviews with or without meta‐analyses (but the overview may also include primary studies).</item> <p></p> <item> Uses a systematic literature search found in the main body of the paper (i.e., search strategy includes text words and MeSH terms in at least two databases).</item> <p></p> <item> Has a methods section in the main body of the paper (not just in the abstract).</item> <p></p> <item> Examines the effects of health interventions or clinical treatments.</item> </ulist> <p>We excluded overviews that based their results solely on primary studies and methodological studies. Reports that were editorials, letters or comments were also excluded. Overviews of risk, exposure, prevention, measurement instruments, quality indicators, diagnostic, screening or prognostic research were excluded. We excluded protocols of overviews.</p> <p> <emph>Inclusion criteria for clinical practice guidelines (CPGs) and health technology assessments (HTAs)</emph>:</p> <p></p> <ulist> <item> Uses an 'overview of review' approach to inform their recommendations (i.e., the CPG aims to primarily include, synthesise and present the results of the systematic reviews; but may also include primary studies).</item> </ulist> <hd id="AN0154579800-7">Search</hd> <p>Overviews were retrieved using a validated search filter for overviews16 from MEDLINE (Ovid), Epistemonikos and the Cochrane Database of Systematic Reviews. In an empirical methods study of the retrieval sensitivity of six databases, the combination of MEDLINE and Epistemonikos retrieved 95.2% of all systematic reviews.17 We are therefore confident that using both a validated search filter and this proven database combination will retrieve the majority of published overviews of healthcare interventions and clinical treatment in the literature.</p> <p>We searched from 2000 to December 2020 (Appendix A). The Epistemonikos search was limited to the category called 'Broad Syntheses', which includes overviews of systematic reviews, health technology assessments and clinical practice guidelines. Epistemonikos contains reports from electronic databases as well as the grey literature, including: PubMed, Embase, The Cumulative Index to Nursing and Allied Health Literature, PsycINFO, Literatura Latinoamericana y del Caribe en Ciencias de la Salud, Database of Abstracts of Reviews of Effects, the Campbell Collaboration's online library, the Joanna Briggs Institute (JBI) Database of Systematic Reviews and Implementation Reports, Cochrane Database of Systematic Reviews and the Evidence for Policy and Practice Information and Co‐ordinating Centre (EPPI‐Centre) Evidence Library.</p> <hd id="AN0154579800-8">Screening and study selection</hd> <p>The initial search results were imported into Excel 2010 for screening. A pilot screening of the first 19 papers was conducted in duplicate by all screeners to ensure high levels of agreement and common definitions of coding. We screened the titles and abstracts against the stated eligibility criteria first, then eligible full‐text articles were reviewed for inclusion. Two independent reviewers screened reports at the title and abstract, and then again at the full text stage, then compared their results (G.S., Y.W.Z., C.L., L.L., P.H.Y., M.D., P.N.). Discrepancies were resolved by consensus, and arbitration by a third reviewer when necessary.</p> <p>Categorised as 'other sources' in our flowchart (Figure 1), 237 overviews were published between 2013 and 2016 were previously identified and screened16,18 (Appendix A), and added to our list of included studies.</p> <p> <img src="https://imageserver.ebscohost.com/img/embimages/rdk/BDCT/01jan22/jrsm1530-fig-0001.jpg?ephost1=dGJyMNXb4kSepq84yOvqOLCmsE6epq5Srqa4SK6WxWXS" alt="jrsm1530-fig-0001.jpg" title="1 PRISMA flowchart of study selection. CPG: clinical practice guideline; HTA, health technology assessment; MA, meta‐analysis; SRs, systematic reviews" /> </p> <p></p> <hd id="AN0154579800-10">Data extraction</hd> <p>We extracted data on overviews published between 2000 and 2018 (<emph>n</emph> = 541) to enable a feasible extraction of data. Data extraction was piloted on 20 studies by all authors independently to identify any missing variables, come to agreement on coding definitions, and refine/reword the items. Discrepancies in the piloting phase were discussed and consensus reached by two authors. Full data extraction was performed independently by one investigator (T.N., A.S., G.S., S.T., S.A., U.E., E.K.R., C.L.), and checked by a second reviewer (T.N., A.S., G.S., S.T., S.A., U.E., E.K.R., C.L.).</p> <p>We extracted the medical field of the overview; year of publication; country and continent (Europe, North America, Asia, Australia, South America, Africa) of corresponding author; number of authors; journal of publication; number of included studies; search date; inclusion of meta‐analysis; and funding status. We also extracted the number of total patients in the included systematic reviews. If the total number was not reported, we added up total patients across all systematic reviews from a table of characteristics. We extracted the number of times the overview had been cited per year via the Google Scholar database, and the 2‐year JIF for the top journals from Web of Science. The JIF, as calculated by Clarivate Analytics, is the ratio of citations to a journal in a given year to the citable items in the prior 2 years. We provide the Journal Citation Reports 2020 (JIF & Ranking of 2019) that we used in Appendix B. When we did not find the JIF in the Clarivate Analytics JOF list, we searched the journal's website for a 2020 JIF. We checked whether the journal was open access via the Directory of Open Access Journals (https://doaj.org/). We also extracted data on the terminology used to describe overviews in the title (overview of reviews, meta‐review, review of reviews or any related synonyms).</p> <p>The medical field categorisation used was the 10th revision of the International Statistical Classification of Diseases and Related Health Problems (ICD), a medical classification list by the World Health Organisation (WHO; https://<ulink href="http://www.who.int/standards/classifications/classification-of-diseases">www.who.int/standards/classifications/classification-of-diseases</ulink>). Time it took to conduct the overview was not reported in the overviews. Therefore, to estimate the time for each overview's search end date to date of publication (i.e., publication lag), we calculated the difference between the most recent search date reported and publication date using the month and day function in Excel 2010. We used the most recent search date in the overview if there were multiple search dates reported.</p> <hd id="AN0154579800-11">Data analysis</hd> <p>Descriptive analysis using frequencies and percentages were performed for categorical data and median and interquartile range (IQR) for continuous data. Citation density was used instead of citation count to avoid bias towards older articles. Citation density was defined as total number of citations divided by the number of years a study has been published. Citation density (the dependent variable) was positively skewed; therefore, the natural log transformation was obtained to approach a normal distribution.</p> <p>Number of overviews published per year were presented in figures. The distribution of overviews by medical discipline and terms used to describe overviews was described. A free version of StatPlanet Plus (<ulink href="http://www.statsilk.com/software/statplanet">http://www.statsilk.com/software/statplanet</ulink>) software was used to create the interactive world map to visualise the distribution of all overviews among different countries.</p> <p>A multivariable regression was conducted to determine the association between six predictor variables (number of authors, open (free) versus closed (paywalled) journal access, number of overviews with meta‐analyses, funding status, sample size, complementary and alternative therapies (CAM) topic) and two dependent variables (citation density and JIF). Statistical significance was set at <emph>p</emph> < 0.05. Statistical analyses were performed using Stata version 13 (StataCorp LP) using two commands manova and mvreg.</p> <hd id="AN0154579800-12">RESULTS</hd> <p></p> <hd id="AN0154579800-13">Search results</hd> <p>From a total of 16,610 records retrieved from the MEDLINE, Cochrane Database of Systematic Reviews, and Epistemonikos databases, and 237 records retrieved from other sources (Figure 1), 2410 duplicates were removed. Of the remaining 14,437 records, 11,481 were excluded at the title/abstract stage, and 1738 were excluded at the full text stage. A total of 1218 overviews were included that met our eligibility criteria, and of these, 541 overviews were published between 2000 and 2018 (44%) were data extracted (data set can be accessed at https://osf.io/38bkg/). Many studies did not have a methods section, did not conduct a systematic search, and did not search for and include systematic reviews (Figure 1).</p> <hd id="AN0154579800-14">Prevalence of overviews</hd> <p>We identified 1218 overviews, CPGs or HTAs published between 2000 and 2020. Between the years of 2000 and 2018, there has been an increase in the publication of overviews (Figure 2). The majority of overviews (886/1218 [73%]) were published between a 5‐year period, from 2016 to 2020. Approximately, three‐quarters of the overviews (1117/1218 [92%]) were published in the most recent decade (2010–2020). An eightfold increase in the number of overviews was found between 2009 (<emph>n</emph> = 25) and 2020 (<emph>n</emph> = 332). We identified 332 overviews published in the three databases in 2020, which is approximately equivalent to 1 overview published per day.</p> <p> <img src="https://imageserver.ebscohost.com/img/embimages/rdk/BDCT/01jan22/jrsm1530-fig-0002.jpg?ephost1=dGJyMNXb4kSepq84yOvqOLCmsE6epq5Srqa4SK6WxWXS" alt="jrsm1530-fig-0002.jpg" title="2 Number of overviews published per year (2000–2020) [Colour figure can be viewed at wileyonlinelibrary.com]" /> </p> <p></p> <hd id="AN0154579800-16">Characteristics of included overviews published between 2000 and 2018 (n  = 541)</hd> <p>Overviews published between 2000 and 2018 were extracted and analysed (<emph>n</emph> = 541). The most frequent subject of the overviews (92/541 [17%]) was ICD‐10 classification 'factors influencing health status and contact with health services'. Another 62/541 (11.5%) focused on diseases of the musculoskeletal system and connective tissue, 56/541 (10.4%) were about mental and behavioural disorders, 42/541 (7.8%) were on diseases of the circulatory system and 34/541 (6.3%) were focused on neoplasms. A little under half of the overviews focused on 15 other conditions in the ICD‐10 medical classification (Table 1).</p> <p>1 TABLECharacteristics of overviews published between 2000 and 2018 (n  = 541)</p> <p> <ephtml> <table><thead valign="bottom"><tr><th align="left">Characteristic</th><th align="left">Category</th><th align="left">Summary data</th></tr></thead><tbody valign="top"><tr><td>ICD‐10 medical classification</td><td>Factors influencing health status and contact with health services</td><td>92 (17%)</td></tr><tr><td>Diseases of the musculoskeletal system and connective tissue</td><td>62 (12%)</td></tr><tr><td>Mental and behavioural disorders</td><td>56 (10%)</td></tr><tr><td>Diseases of the circulatory system</td><td>42 (8%)</td></tr><tr><td>Neoplasms</td><td>34 (6%)</td></tr><tr><td>Diseases of the nervous system</td><td>27 (5%)</td></tr><tr><td>Diseases of the respiratory system</td><td>27 (5%)</td></tr><tr><td>Other (13 more ICD‐10 classifications with under 26 overviews per topic)</td><td>201 (37%)</td></tr><tr><td>Complementary and alternative medicine focused journal</td><td>29 (5%)</td></tr><tr><td>Number of authors per overview</td><td>1</td><td>22 (4%)</td></tr><tr><td>2–3</td><td>163 (30%)</td></tr><tr><td>4–6</td><td>219 (41%)</td></tr><tr><td>7–10</td><td>88 (16%)</td></tr><tr><td>11–20</td><td>36 (7%)</td></tr><tr><td>>21</td><td>8 (2%)</td></tr><tr><td>Total number of countries of corresponding authors</td><td>42</td></tr><tr><td>Country of corresponding author</td><td>United Kingdom</td><td>140 (26%)</td></tr><tr><td>United States</td><td>65 (12%)</td></tr><tr><td>Canada</td><td>53 (10%)</td></tr><tr><td>Australia</td><td>42 (8%)</td></tr><tr><td>China</td><td>34 (6%)</td></tr><tr><td>Germany</td><td>33 (6%)</td></tr><tr><td>The Netherlands</td><td>27 (5%)</td></tr><tr><td>Brazil</td><td>24 (4%)</td></tr><tr><td>Other (34 more countries with under 10 overviews)</td><td>123 (23%)</td></tr><tr><td>Continent of corresponding author</td><td>Europe</td><td>267 (49%)</td></tr><tr><td>North America</td><td>125 (23%)</td></tr><tr><td>Asia</td><td>61 (11%)</td></tr><tr><td>Australia/NZ</td><td>46 (9%)</td></tr><tr><td>South America</td><td>37 (7%)</td></tr><tr><td>Africa</td><td>5 (1%)</td></tr><tr><td>Presence of meta‐analysis</td><td>No</td><td>465 (86%)</td></tr><tr><td>Yes</td><td>76 (14%)</td></tr><tr><td>Funding</td><td>Not reported</td><td>269 (50%)</td></tr><tr><td>Reported</td><td>272 (50%)</td></tr><tr><td>Number of included SRs (sample size)</td><td>Mean (SD)</td><td>24.3 (32)</td></tr><tr><td>Publication lag (time from search end date to date of publication)</td><td>Mean (SD)</td><td align="left">1.6 years (2.3)</td></tr><tr><td>Number of included patients</td><td>Mean (SD)</td><td>109.7 (113.4)</td></tr><tr><td>Overview that directly informed a clinical practice guideline</td><td>17 (3%)</td></tr><tr><td>Clinical practice guideline (using an overview of reviews for evidence synthesis)</td><td>30 (6%)</td></tr><tr><td>Cochrane overviews</td><td /><td>44 (8%)</td></tr></tbody></table> </ephtml> </p> <p>1 <emph>Note</emph>: Summary data given as number (%) or median (IQR).</p> <p>2 Abbreviations: ICD: 10th revision of the International Statistical Classification of Diseases and Related Health Problems; IQR: interquartile range; SD, standard deviation; SRs: systematic reviews.</p> <p>Several authors working on one overview was common; the average authorship per overview was 5.3, with number of authors ranging from 1 to 24. Overviews most frequently had 4 to 6 authors (219 [41%]) on the team. Corresponding authors were most frequently from the United Kingdom (140/541 [26%]), the United States (65/541 [12%]) or Canada (53/541 [10%]) (Figure 3). The largest proportion of overviews (267/541 [49%]) had a corresponding author from Europe while the smallest proportion of overviews (5/541 [1%]) had a corresponding author from Africa. The median number of included systematic reviews was 14 (interquartile range [IQR] 7–27), and the mean number of patients was 110. A majority (465/541 [86%]) did not conduct a meta‐analysis, and half (272/541 [50%]) reported funding sources. The mean time from search to publication was 1.6 years.</p> <p> <img src="https://imageserver.ebscohost.com/img/embimages/rdk/BDCT/01jan22/jrsm1530-fig-0003.jpg?ephost1=dGJyMNXb4kSepq84yOvqOLCmsE6epq5Srqa4SK6WxWXS" alt="jrsm1530-fig-0003.jpg" title="3 Map of country of corresponding authors of overviews published between 2000 and 2018 (n = 541) [Colour figure can be viewed at wileyonlinelibrary.com]" /> </p> <p></p> <hd id="AN0154579800-18">Journals, JIF and citation density of overviews published between 2000 and 2018 (n  = 541)</hd> <p>A total of 541 overviews were published in 307 journals between 2000 and 2018 (Table 2). The majority of overviews (369/528 [70%]) were published in journals with JIFs between 0.05 and 3.97. Thirty percent of overviews (159/528) were published in journals with JIFs of 4 or greater. Twenty overviews were published in journals with JIFs between 17 and 59 (e.g., <emph>The Lancet, BMJ, JAMA</emph>). The <emph>Cochrane Database of Systematic Reviews</emph> published the largest number of overviews (44/538 [8%]), followed by <emph>PLOS ONE</emph> (16/538 [3%]), the <emph>Sao Paulo Medical Journal</emph> (12/538 [2%]) and <emph>BMJ Clinical Evidence</emph> (10/538 [1.9%]). About half (227/538 [42%]) of the overviews were published in unique journals (i.e., only one overview published in that journal). A total of 130 overviews (24%) were published in open access journals or chose an open access option when publishing.</p> <p>2 TABLEJournals, JIF, and citation density of 541 overviews published between 2000 and 2018</p> <p> <ephtml> <table><thead valign="bottom"><tr><th align="left">Journal characteristic</th><th align="left">Category</th><th align="left">Summary data</th></tr></thead><tbody valign="top"><tr><td>Number of journals</td><td>307</td></tr><tr><td>Number of overviews per journal</td><td>1</td><td>227</td></tr><tr><td>2–4</td><td>56</td></tr><tr><td>5–10</td><td>18</td></tr><tr><td>11–16</td><td>2</td></tr><tr><td>44</td><td>1</td></tr><tr><td>Journals</td><td>Cochrane Database of Systematic Reviews</td><td>44 (8%)</td></tr><tr><td>PLOS ONE</td><td>16 (3%)</td></tr><tr><td>Sao Paulo Medical Journal</td><td>12 (2%)</td></tr><tr><td>BMJ Clinical Evidence</td><td>10 (1.8%)</td></tr><tr><td>BMJ Open</td><td>7 (1.3%)</td></tr><tr><td>British Journal of Sports Medicine</td><td>7 (1.3%)</td></tr><tr><td>Maturitas</td><td>7 (1.3%)</td></tr><tr><td>Other (<299 journals)</td><td>439 (81%)</td></tr><tr><td>Journal impact factor</td><td>0.01–1.99</td><td>153 (29%)</td></tr><tr><td>2.0–3.97</td><td>216 (41%)</td></tr><tr><td>4.0–6.96</td><td>61 (11%)</td></tr><tr><td>7.0–12.79</td><td>79 (14%)</td></tr><tr><td>13.6–59.1</td><td>23 (4%)</td></tr><tr><td>Median (IQR)</td><td>2.8 (1.9–4.6)</td></tr><tr><td>Open access journals</td><td /><td>130 (24%)</td></tr><tr><td>Citation Density</td><td>0.0–1.0</td><td>78 (14.4%)</td></tr><tr><td>1.1–3.0</td><td>79 (14.6%)</td></tr><tr><td>3.1–5.0</td><td>62 (11.5%)</td></tr><tr><td>5.1–10.0</td><td>98 (18.1%)</td></tr><tr><td>10.3–20.0</td><td>117 (21.6%)</td></tr><tr><td>20.1–40.4</td><td>62 (11.5%)</td></tr><tr><td>40.5–329</td><td>44 (8.1%)</td></tr><tr><td>Median (IQR)</td><td>8.5 (3.5–18.3)</td></tr><tr><td>Citation count over 9 years</td><td>Mean (SD)</td><td>90 (219.7)</td></tr></tbody></table> </ephtml> </p> <ulist> <item>3 <emph>Note</emph>: Summary data given as number (%) or median (IQR).</item> <item>4 Abbreviations: IQR: interquartile range; SD: standard deviation; SRs: systematic reviews.</item> </ulist> <p>We found an average citation rate of 90 (SD ±219.7) over 9 years, or 10 citations per overview per year. Four reports did not have a JIF and did not have citation counts and were therefore omitted from this analysis. When examining overviews published in the top 50 journals by JIFs (≥7.86), we found that 50 overviews (9%; 50/537) received 18% of citations (range 4–1250). Nine overviews remained un‐cited. A total of 108 out of 537 overviews (20%) were cited 100 times or more. An article having 100 or more citations is regarded as a 'classic'.19 The topics of the six overviews with citations counts of >1000 included two on diseases of the musculoskeletal system and connective tissue, two on factors influencing health status and contact with health services, and one each on pregnancy, childbirth and the puerperium; and mental and behavioural disorders.</p> <hd id="AN0154579800-19">Nomenclature of 541 overviews published between 2000 and 2018</hd> <p>Overall, 14% (73/541) of the overviews did not use any terms or synonyms to identify the study as an overview (Appendix C). Of the 541 overviews, the majority used the term overview (196/541 [36%]) and 'systematic review of reviews' (74/541 [14%]) or a close derivative in the title (Appendix C). Synonyms and other terms were used less frequently; 42 overviews (8%) used the term umbrella review, and 19 (4%) used the term meta‐review (3%) in the title. The term 'systematic review' was used in 33/541 (7%) to mean an overview.</p> <p>A word cloud was created to visualise the frequency of words and phrases used, with the sizes of words and phrases representing the frequency (Figure 4).</p> <p> <img src="https://imageserver.ebscohost.com/img/embimages/rdk/BDCT/01jan22/jrsm1530-fig-0004.jpg?ephost1=dGJyMNXb4kSepq84yOvqOLCmsE6epq5Srqa4SK6WxWXS" alt="jrsm1530-fig-0004.jpg" title="4 Word cloud of terms in titles describing 541 overviews published between 2000 and 2018 [Colour figure can be viewed at wileyonlinelibrary.com]" /> </p> <p></p> <hd id="AN0154579800-21">Multivariable regression</hd> <p>Two separate multivariable analyses (one for JIF and one for citation density). were conducted with various potential predictors. Controlling for the other variables in the model, citation density and JIF were positively and significantly correlated with the number of authors, sample size, funding reported and open access articles (Appendix D). This indicates that overviews with a high number of citations and high JIFs tend to have a higher number of authors, larger sample sizes, be open access and report sources of funding. The multiple regression model with JIF, and four predictors, produced <emph>R</emph><sups>2</sups> = 0.119, <emph>F</emph>(<reflink idref="bib5" id="ref1">5</reflink>, 514) = 17.18, <emph>p</emph> < 0.001 and citation density and four predictors produced <emph>R</emph><sups>2</sups> = 0.126, <emph>F</emph>(<reflink idref="bib5" id="ref2">5</reflink>, 514) = 18.31, <emph>p</emph> < 0.001. Overviews on topics related to CAM and overviews using a meta‐analysis were not associated with citation density and JIF, and were therefore not included in the model.</p> <hd id="AN0154579800-22">DISCUSSION</hd> <p></p> <hd id="AN0154579800-23">Summary of results</hd> <p>To our knowledge, this is the first study to examine the annual publication prevalence, predictors of citation rates and JIFs of overviews. This bibliometrics study provides a baseline of publication trends and impact of overviews, and the list of overviews identified can be used in future methods studies. The number of overviews has increased over the last 20 years, with 73% of the overviews published in the most recent 5‐year period (2016–2020). In 2020, one overview was published per day. The majority of overviews had 4–6 authors on the team, and took on average 1.6 years to produce from search date to publication. Most overviews were published on the medical categories of health systems and services, musculoskeletal system and mental disorders. The journals that publish the most overviews were the Cochrane Database of Systematic Reviews, PLOS ONE and the Sao Paulo Medical Journal, but each with <10% of the published overview sample.</p> <hd id="AN0154579800-24">Prevalence of overviews</hd> <p>We found an eightfold increase in the number of overviews between 2009 (<emph>n</emph> = 25) and 2020 (<emph>n</emph> = 332). An annual increasing prevalence of overviews has been found by other authors. One study found that the number of overviews increased from 1 in 2000 to 14 in 201020 and another found a five‐fold increase in the publication of overviews from 2004 to 2011.14 The factors driving the increase in overviews are explained by the exponential increase in the number of systematic reviews being published, the publication of guidance on how to conduct an overview of reviews by Cochrane as of 2009, and the subsequent publication of the first Cochrane overview in the same year.</p> <hd id="AN0154579800-25">Higher citation rate of overviews</hd> <p>We found that the average citation rate for overviews was 90 (SD ±219.7) over 9 years, or 10 citations per overview per year. Several studies have found that systematic reviews and meta‐analyses have higher citation counts than RCTs or observational studies.4,21–24 Mean citation counts for systematic reviews and meta‐analyses ranged from 0.74,4 5.123 to 6.6 per year.24 Our study found a significantly higher mean citation count of 10 overviews per year than these studies on reviews. The mean JIF of the journals the overviews publish is was 4.4. These data indicate that, overall, overviews perform above average for the journals in which they publish, and therefore may contribute to increasing the 2‐year JIFs of the journals in which they are published.</p> <hd id="AN0154579800-26">Terminology</hd> <p>Currently identifying and searching for overviews is problematic because there is no agreed nomenclature, and no standardised definition. One of the first overviews was published in 199225; however, it only became recognised as such after 2009, when Cochrane published guidance for overviews and its first overview in the Cochrane library.</p> <p>We found that only one third of our sample used the term overview in the title, 12% used umbrella review or meta‐review and 14% used systematic review of reviews, or a close derivative. Of concern is that 7% used the term 'systematic review' to mean an overview of reviews. Inconsistent nomenclature may have affected the performance of our search filter used in this study. Overviews entitled 'systematic reviews' would be miscoded into MEDLINE's Publication Type (PT) for systematic reviews, leading to a compounding problem. Overviews should have their own Publication Type (PT) term in MEDLINE to help differentiate systematic reviews from overviews.16</p> <p>A consistent nomenclature for overviews would help in the identification of overviews. We recommend that authors of overviews use the term <emph>overview of systematic reviews</emph> in the title to help users search for and identify relevant reports.</p> <hd id="AN0154579800-27">Predictors of citation and JIF</hd> <p>In our large sample, overviews with a high number of citations and high JIFs had group authorship, large sample sizes, were open access, and reported sources of funding. Several studies of citation counts and JIFs in the health field identified predictors of citation rates similar to our own, namely number of authors, sample size, funding status and open access.21,22,24,26,27</p> <hd id="AN0154579800-28">Strengths and limitations</hd> <p>The main strength of this study is that it is the first to look at predictors of citations and JIF specific to overviews published over a wide range of subject areas and journals, and it included a number of characteristics of both the article itself and the journal in which it appeared. Other strengths include comprehensiveness of years searched, the large number of extracted articles (<emph>n</emph> = 541), and our strict eligibility criteria for overviews. We also search a combination of databases (MEDLINE, Epistemonikos and Cochrane) with a high sensitivity (over 95%) in retrieving overviews in all medical fields.17</p> <p>A limitation to our study is that we may not have captured the actual number of overviews published as we only searched three databases and did not search the grey literature. Furthermore, we used a verification system for data extraction rather than independent extraction, which may not be as robust as what Cochrane standards are for Cochrane reviews. Less rigorously developed overviews, such as those only searching one database, were not included. Also, our selected overviews were limited to those pertaining to therapeutic, clinical and health intervention topics. In addition, the 541 analysed do not represent the whole sample of 1218 overviews, this limiting generalizability of our findings.</p> <p>Our ability to predict the variance of annual citation rates was weak (13%); however, it is consistent with other similar studies. One study predicted 14% of the variance of annual citation rates using emergency medicine studies and 12 possible predictor variables,28 and another study predicted 20% using articles from three high impact journals.26</p> <hd id="AN0154579800-29">Future research</hd> <p>The research provides a baseline of publication trends and impact of overviews for future research. Future research could also explore whether the quality of conduct of overviews predicted citation density. An examination of the top 100 cited overviews compared to those least cited would inform authors about what factors contribute to citation rate. In addition, future investigations should explore social media impact metrics (e.g., Altmetric score) and other article metrics, and composition of overview author networks. Finally, this compilation of 1218 overviews represents a bibliographic database of all overviews published in healthcare interventions or clinical treatments from 2000 to 2020 and can be used by methodologists interested in studying this review type.</p> <hd id="AN0154579800-30">CONCLUSIONS</hd> <p>This 20‐year bibliometric study is the first of its kind to identify and characterise overviews across 307 journals indexed in three databases. The eightfold increase in the number of overviews from the publication of the Cochrane guidance for overviews in 2009–2020 illustrates the increasing popularity and demand for overviews. This demand is due potentially to the need to synthesise the results of multiple reviews on topics of broad scope, and of relevance to policy and practice.</p> <p>Many academics, practitioners and policy makers have failed to see the impact and utility of overviews, and their potential to inform clinical practice, policy and guideline development. Citation analysis and JIF metrics can help these knowledge users to quantify, compare and communicate the influence of overviews of reviews. Our study found a mean citation count of 10 overviews per year, published in journals with a mean JIF of 4.4. These data indicate that, overall, overviews perform above average for the journals in which they publish, and therefore may contribute to increasing their 2‐year JIFs. We also found that highly cited overviews in journals with high JIFs are associated with group authorship, large sample sizes, open access publishing and reported sources of funding. The study provides a baseline of annual publication trends and bibliometric impact of overviews for future research.</p> <hd id="AN0154579800-31">CONFLICT OF INTEREST</hd> <p>The authors declare no conflict of interest.</p> <hd id="AN0154579800-32">AUTHOR CONTRIBUTIONS</hd> <p>Carole Lunny conceived of the study design, wrote the study protocol, analysed the data, wrote and revised the final manuscript. Gavindeep Shinger, Yi Wen Zheng, Carole Lunny, Lester Lin, Pei Hsuan Yang, Manpreet Dosanjh, Peter Ngsee screened citations and full‐text articles. Trish Neelakant, Adrienne Stevens, Gavindeep Shinger, Sara Tasnim, Stephen Adams, Ursula Ellis, Emma K. Reid abstracted and verified data. Carole Lunny, Trish Neelakant, Alyssa Chen, Gavindeep Shinger, Shadi Sadeghipouya analysed the data. Carole Lunny, Alyssa Chen, Adrienne Stevens, Beverley J. Shea interpreted results, and edited the manuscript. Trish Neelakant, Alyssa Chen, Gavindeep Shinger, Adrienne Stevens, Sara Tasnim, Shadi Sadeghipouya, Stephen Adams, Yi Wen Zheng, Lester Lin, Pei Hsuan Yang, Manpreet Dosanjh, Peter Ngsee, Ursula Ellis, Beverley J. Shea, Emma K. Reid, and James M. Wright edited and approved of the final manuscript.</p> <hd id="AN0154579800-33">DATA AVAILABILITY STATEMENT</hd> <p>The full dataset is available on https://osf.io/38bkg.</p> <p>GRAPH: Appendix A – Search StrategyAppendix B ‐ Journal Citation Reports 2020 (JIF & Ranking of 2019)Appendix C – Terminology for overviewsAppendix D ‐ Multivariable regression analysis</p> <ref id="AN0154579800-34"> <title> REFERENCES </title> <blist> <bibl id="bib1" type="bt">1</bibl> <bibtext> Retrouvey H, Webster F, Zhong T, Gagliardi AR, Baxter NN. Cross‐sectional analysis of bibliometrics and altmetrics: comparing the impact of qualitative and quantitative articles in the British medical journal. BMJ Open. 2020 ; 10 (10): e040950.</bibtext> </blist> <blist> <bibl id="bib2" type="bt">2</bibl> <bibtext> Brandt JS, Hadaya O, Schuster M, Rosen T, Sauer MV, Ananth CV. A Bibliometric analysis of top‐cited journal articles in obstetrics and gynecology. JAMA Netw Open. 2019 ; 2 (12): e1918007 ‐ e1918007.</bibtext> </blist> <blist> <bibl id="bib3" type="bt">3</bibl> <bibtext> Trueger NS, Yilmaz Y, Chan TM. Leveraging tweets, citations, and social networks to improve Bibliometrics. JAMA Netw Open. 2020 ; 3 (7): e2010911.</bibtext> </blist> <blist> <bibl id="bib4" type="bt">4</bibl> <bibtext> Allareddy V, Lee MK, Shah A, Elangovan S, Lin CY. Association between study design and citation counts of articles published in the American journal of orthodontics and Dentofacial orthopedics and angle orthodontist. Orthodontics (Chic). 2012 ; 13 (1): 184 ‐ 191.</bibtext> </blist> <blist> <bibl id="bib5" idref="ref1" type="bt">5</bibl> <bibtext> Montori VM, Wilczynski NL, Morgan D, Haynes RB. 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J Clin Epidemiol. 2020 ; 118 : 69 ‐ 85.</bibtext> </blist> <blist> <bibtext> Andersen J, Belmont J, Cho CT. Journal impact factor in the era of expanding literature. J Microbiol Immunol Infection. 2006 ; 39 (6): 436 ‐ 443.</bibtext> </blist> <blist> <bibtext> Hartling L, Chisholm A, Thomson D, Dryden DM. A descriptive analysis of overviews of reviews published between 2000 and 2011. PLoS One. 2012 ; 7 (11): e49667.</bibtext> </blist> <blist> <bibtext> Lokker C, McKibbon KA, McKinlay RJ, Wilczynski NL, Haynes RB. Prediction of citation counts for clinical articles at two years using data available within three weeks of publication: retrospective cohort study. BMJ. 2008 ; 336 (7645): 655 ‐ 657.</bibtext> </blist> <blist> <bibtext> Tahamtan I, Afshar AS, Ahamdzadeh K. Factors affecting number of citations: a comprehensive review of the literature. Scientometrics. 2016 ; 107 (3): 1195 ‐ 1225.</bibtext> </blist> <blist> <bibtext> Bhandari M, Busse J, Devereaux PJ, et al. Factors associated with citation rates in the orthopedic literature. Canadian J Surg. 2007 ; 50 (2): 119 ‐ 123.</bibtext> </blist> <blist> <bibtext> Royle P, Kandala N‐B, Barnard K, Waugh N. Bibliometrics of systematic reviews: analysis of citation rates and journal impact factors. Syst Rev. 2013 ; 2 (1): 74.</bibtext> </blist> <blist> <bibtext> Antman EM, Lau J, Kupelnick B, Mosteller F, Chalmers TC. A comparison of results of meta‐analyses of randomized control trials and recommendations of clinical experts. Treatments for myocardial infarction. JAMA. 1992 ; 268 (2): 240 ‐ 248.</bibtext> </blist> <blist> <bibtext> Kulkarni AV, Busse JW, Shams I. Characteristics associated with citation rate of the medical literature. PLoS One. 2007 ; 2 (5): e403.</bibtext> </blist> <blist> <bibtext> Davis PM, Lewenstein BV, Simon DH, Booth JG, Connolly MJL. Open access publishing, article downloads, and citations: randomised controlled trial. BMJ. 2008 ; 337 : a568.</bibtext> </blist> <blist> <bibtext> Callaham M, Wears RL, Weber E. Journal prestige, publication bias, and other characteristics associated with citation of published studies in peer‐reviewed journals. JAMA. 2002 ; 287 (21): 2847 ‐ 2850.</bibtext> </blist> </ref> <aug> <p>By Carole Lunny; Trish Neelakant; Alyssa Chen; Gavindeep Shinger; Adrienne Stevens; Sara Tasnim; Shadi Sadeghipouya; Stephen Adams; Yi Wen Zheng; Lester Lin; Pei Hsuan Yang; Manpreet Dosanjh; Peter Ngsee; Ursula Ellis; Beverley J. Shea; Emma K. Reid and James M. Wright</p> <p>Reported by Author; Author; Author; Author; Author; Author; Author; Author; Author; Author; Author; Author; Author; Author; Author; Author; Author</p> </aug>
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  Data: Bibliometric Study of 'Overviews of Systematic Reviews' of Health Interventions: Evaluation of Prevalence, Citation and Journal Impact Factor
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  Data: <searchLink fieldCode="AR" term="%22Lunny%2C+Carole%22">Lunny, Carole</searchLink> (ORCID <externalLink term="https://orcid.org/0000-0002-7825-6765">0000-0002-7825-6765</externalLink>)<br /><searchLink fieldCode="AR" term="%22Neelakant%2C+Trish%22">Neelakant, Trish</searchLink><br /><searchLink fieldCode="AR" term="%22Chen%2C+Alyssa%22">Chen, Alyssa</searchLink><br /><searchLink fieldCode="AR" term="%22Shinger%2C+Gavindeep%22">Shinger, Gavindeep</searchLink><br /><searchLink fieldCode="AR" term="%22Stevens%2C+Adrienne%22">Stevens, Adrienne</searchLink> (ORCID <externalLink term="https://orcid.org/0000-0002-6257-4806">0000-0002-6257-4806</externalLink>)<br /><searchLink fieldCode="AR" term="%22Tasnim%2C+Sara%22">Tasnim, Sara</searchLink><br /><searchLink fieldCode="AR" term="%22Sadeghipouya%2C+Shadi%22">Sadeghipouya, Shadi</searchLink><br /><searchLink fieldCode="AR" term="%22Adams%2C+Stephen%22">Adams, Stephen</searchLink><br /><searchLink fieldCode="AR" term="%22Zheng%2C+Yi+Wen%22">Zheng, Yi Wen</searchLink><br /><searchLink fieldCode="AR" term="%22Lin%2C+Lester%22">Lin, Lester</searchLink><br /><searchLink fieldCode="AR" term="%22Yang%2C+Pei+Hsuan%22">Yang, Pei Hsuan</searchLink><br /><searchLink fieldCode="AR" term="%22Dosanjh%2C+Manpreet%22">Dosanjh, Manpreet</searchLink><br /><searchLink fieldCode="AR" term="%22Ngsee%2C+Peter%22">Ngsee, Peter</searchLink><br /><searchLink fieldCode="AR" term="%22Ellis%2C+Ursula%22">Ellis, Ursula</searchLink> (ORCID <externalLink term="https://orcid.org/0000-0002-5896-4852">0000-0002-5896-4852</externalLink>)<br /><searchLink fieldCode="AR" term="%22Shea%2C+Beverley+J%2E%22">Shea, Beverley J.</searchLink> (ORCID <externalLink term="https://orcid.org/0000-0002-7686-2585">0000-0002-7686-2585</externalLink>)<br /><searchLink fieldCode="AR" term="%22Reid%2C+Emma+K%2E%22">Reid, Emma K.</searchLink><br /><searchLink fieldCode="AR" term="%22Wright%2C+James+M%2E%22">Wright, James M.</searchLink>
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  Label: Abstract
  Group: Ab
  Data: Overviews synthesising the results of multiple systematic reviews help inform evidence-based clinical practice. In this first of two companion papers, we evaluate the bibliometrics of overviews, including their prevalence and factors affecting citation rates and journal impact factor (JIF). We searched MEDLINE, Epistemonikos and Cochrane Database of Systematic Reviews (CDSR). We included overviews that: (1) synthesised reviews; (2) conducted a systematic search; (3) had a methods section; and (4) examined a healthcare intervention. Multivariable regression was conducted to determine the association between citation density, JIF and six predictor variables. We found 1218 overviews published from 2000 to 2020; the majority (73%) were published in the most recent 5-year period. We extracted a selection of these overviews (n = 541; 44%) dated from 2000 to 2018. The 541 overviews were published in 307 journals; "CDSR" (8%), "PLOS ONE" (3%) and "Sao Paulo Medical Journal" (2%) were the most prevalent. The majority (70%) were published in journals with impact factors between 0.05 and 3.97. We found a mean citation count of 10 overviews per year, published in journals with a mean JIF of 4.4. In multivariable analysis, overviews with a high number of citations and JIFs had more authors, larger sample sizes, were open access and reported the funding source. An eightfold increase in the number of overviews was found between 2009 and 2020. We identified 332 overviews published in 2020, which is equivalent to one overview published per day. Overviews perform above average for the journals in which they publish.
– Name: AbstractInfo
  Label: Abstractor
  Group: Ab
  Data: As Provided
– Name: Note
  Label: Notes
  Group: Note
  Data: https://osf.io/38bkg
– Name: DateEntry
  Label: Entry Date
  Group: Date
  Data: 2022
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  Group: ID
  Data: EJ1323669
PLink https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=eric&AN=EJ1323669
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    Identifiers:
      – Type: doi
        Value: 10.1002/jrsm.1530
    Languages:
      – Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 12
        StartPage: 109
    Subjects:
      – SubjectFull: Bibliometrics
        Type: general
      – SubjectFull: Citation Analysis
        Type: general
      – SubjectFull: Journal Articles
        Type: general
      – SubjectFull: Periodicals
        Type: general
      – SubjectFull: Medicine
        Type: general
      – SubjectFull: Literature Reviews
        Type: general
      – SubjectFull: Meta Analysis
        Type: general
      – SubjectFull: Predictor Variables
        Type: general
      – SubjectFull: Incidence
        Type: general
      – SubjectFull: Sample Size
        Type: general
      – SubjectFull: Access to Information
        Type: general
      – SubjectFull: Open Educational Resources
        Type: general
    Titles:
      – TitleFull: Bibliometric Study of 'Overviews of Systematic Reviews' of Health Interventions: Evaluation of Prevalence, Citation and Journal Impact Factor
        Type: main
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            – D: 01
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              Type: published
              Y: 2022
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              Value: 1759-2879
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              Value: 13
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            – TitleFull: Research Synthesis Methods
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