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Anesth Analg 2007; 105:1741-1746
© 2007 International Anesthesia Research Society
doi: 10.1213/01.ane.0000286149.57763.e7
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GENERAL ARTICLES

A Bibliometric Analysis of Global Clinical Research by Anesthesia Departments

Madhav Swaminathan, MD, FASE, FAHA, Barbara G. Phillips-Bute, PhD, and Katherine P. Grichnik, MD, FASE

From the Division of Cardiothoracic Anesthesiology and Critical Care Medicine, Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina.

Address correspondence to Madhav Swaminathan, MD, FASE, FAHA, Duke University Medical Center, Department of Anesthesiology, Box 3094, Durham, NC 27710. Address e-mail to swami001{at}mc.duke.edu.


   Abstract
Top
 Abstract
Introduction
 METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
BACKGROUND: Few studies have investigated the diversity in research conducted by anesthesia-based researchers. We examined global clinical research attributed to anesthesia departments using Medline® and Ovid® databases. We also investigated the impact of economic development on national academic productivity.

METHODS: We conducted a Medline search for English-language publications from 2000 to 2005. The search included only clinical research in which institutional affiliation included words relating to anesthesia (e.g., anesthesiology, anesthesia, etc.). Population and gross national income data were obtained from publicly available databases. Impact factors for journals were obtained from Journal Citation Reports (Thomson Scientific).

RESULTS: There were 6736 publications from 64 countries in 551 journals. About 85% of all publications were represented by 46 journals. Randomized controlled trials constituted 4685 (70%) of publications. Turkey had the highest percentage of randomized controlled trials (88%). The United States led the field in quantity (20% of total) and mean impact factor (3.0) of publications. Finland had the highest productivity when adjusted for population (36 publications per million population). Publications from the United States declined from 23% in 2000 to 17% in 2005.

CONCLUSIONS: Clinical research attributable to investigators in our specialty is diverse, and extends beyond the traditional field of anesthesia and intensive care. The United States produces the most clinical research, but per capita output is higher in European nations.


   Introduction
Top
 Abstract
 Introduction
METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Medical progress is dependent on scientific communication of research findings. There has been a significant increase in the volume of scientific publications in recent years. Several studies have documented patterns of publications in clinical and basic science research in anesthesia journals (1–4). Some investigators have also determined the contribution of specific countries and regions to the anesthesia literature (1). Most reports have focused on bibliometric analyses of publications within the subject category of anesthesia or anesthesia-related research. However, the clinical practice of anesthesia encompasses several disciplines, and anesthesiologists publish in journals serving a diverse scientific audience. For instance, research attributed to anesthesia departments is published on such diverse subjects as clinical toxicology and aviation space medicine. This diversity in clinical research among anesthesia departments has not been quantified or reported. A significant limitation to studying this diversity has been the lack of consistent information on institutional or departmental affiliation of the corresponding author among journals.

From 1988 onwards, Medline® database elements included primary author affiliation. However, this information was more consistent after 1996 when electronic submissions were introduced and the author's email address was also included when available (5). This field has detailed information on the author's complete address, including department information when available. Using Medline and other publicly available databases, we examined global clinical research productivity by anesthesiologists, and tabulated trends by country.


   METHODS
Top
 Abstract
 Introduction
 METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
With IRB approval, we gathered bibliometric data from 2000 to 2005 using Medline. The search was conducted using the Ovid Gateway for Medline (Thomson Scientific, Philadelphia, PA). A hierarchy of search terms was used (Table 1) using a combination of Boolean operators (AND, OR, NOT) to extract English language human clinical research attributable to institutional affiliation that included any of the most common anesthesia-related words. Clinical research was defined as a publication that was indexed by Medline under the "publication type" field under one or more specific headings indicated in Table 1. A comprehensive description of publication characteristics in the "publication type" field is available on the Medline website (http://www.nlm.nih.gov/mesh/pubtypes2006.html [accessed on May 10, 2007]). The search was repeated for each year from 2000 to 2005. These specific years were chosen since information on author address and institutional affiliation was likely to be accurate from 2000 onwards, whereas impact factor data were available for journals only until 2005 at the time of writing. Citations matching the search criteria were imported into the EndNote® bibliographic management software (Thomson Scientific). Review articles, case reports, letters to the editor, errata, and duplicate publications were excluded from the database.


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  		Table 1. Search Criteria

 

Quality of publications was defined by two criteria 1) type of publication (Table 1), and 2) impact factor of journal. Among the different publication types, a hierarchy was established in the following descending order of importance: randomized controlled trials, controlled clinical trials, clinical trials, evaluation and/or validation studies, and finally, meta-analyses. Journal impact factors were gathered for all journals represented in the database for the latest year (2005) from Journal Citation Reports® (ISI Web of Knowledge, Thomson Scientific). Country labels were individually collected from the "author address" field in EndNote for each publication. Publications from Northern Ireland, England, Scotland, and Wales were grouped as United Kingdom. Publications from Hong Kong were not grouped with China because there were different quantitative variables for the two regions.

Country-specific data were then gathered from two sources: (a) population information was obtained from the United Nations Populations Division for the most recent reported period for each country (6), and (b) statistics on income category for each country were acquired from the World Bank List of Economies for 2005 (7). Briefly, 208 countries are classified by the World Bank according to 2005 Gross National Income per capita as low income ($875 or less), lower middle income ($876–$3465), upper middle income ($3466–$10,725), and high income (>$10,726). A complete description of this methodology and countries included is available on the World Bank website (7). Both sources are publicly available through online searchable databases. Separate databases were developed for publications, country-specific data and journal-specific data. The data were then analyzed using SAS statistical software (version 9.1.3, SAS, Cary, NC) with cross tabulations between individual databases.

Descriptive statistics were used to examine the quality of publications from each country (countrywise impact factor and type of publication), national productivity per capita of population, and impact of economic category on productivity. In addition, journals represented in this database were quantified in terms of number of publications for each journal.


   RESULTS
Top
 Abstract
 Introduction
 METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
There were 6736 publications that met inclusion criteria from 2000 to 2005. The number was fairly consistent over the timeline (Fig. 1) with a mean of 1123 ± 68 publications per year. These publications were represented by authors from 64 countries and appeared in 551 journals. Approximately 85% of the publications were represented by 46 of the 551 journals (Table 2). Two hundred fifty-eight journals had only one publication each, whereas 90 journals had two publications, and 47 had three publications.


Figure 138
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  		Figure 1. Total number of publications including United States contribution. United States contribution is expressed as percent of total (line trend with scale on y axis on right).

 

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  		Table 2. Journal Representation

 

Among the 64 countries represented in the database, 34 had 20 or more publications (Table 3). These countries accounted for 6582 of the total 6736 publications (98%). The United States led with 1295 publications (20%). Western Europe contributed 3033 publications (45%), whereas Asia contributed 1367 publications (20%).


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  		Table 3. Country Representation

 

Qualitative Variables
By Publication Type
Randomized controlled trials constituted a majority of the publications (4685 of 6736; 70%). Clinical trials and controlled clinical trials were next at 22%, followed by evaluation or validation studies (7%) and meta-analyses (2%). The country with the highest proportion of randomized controlled trails was Turkey (88%).

By Impact Factor
Impact factor information was available for 415 of the 551 journals that represented 92% of the total number of publications. The mean impact factor for all publications was 2.12. Mean impact factor was uninterpretable when there were few publications. For example, publications from Russia had the highest mean impact factor (5.08), but only one publication, and the nine publications from Columbia had a mean impact factor of 3.21. Among the 34 countries with more than 20 publications, publications from United States had the highest mean impact factor (3.04).

Quantitative Parameters
The United States had the most publications each year. However, publications from the United States declined from 23% in 2000 to 17% in 2005 (Fig. 1). Finland had the most publications per capita, 36 publications per million people, despite an overall publication rank of 10th with 187 publications in 6 yr.

Analysis of by national income produced expected results (Fig. 2). Among the top 34 countries with 20 or more publications, the 24 high income countries published a median of 8.5 manuscripts per million people (range 1.7 [Spain] to 35.6 [Finland]). The 10 countries not classified as high income nations published a median of 0.3 manuscripts per million people (range 0.1 [India, Pakistan, China, and Brazil] to 11.7 [Lebanon]).


Figure 238
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  		Figure 2. Distribution of all publications by national income category. All 64 countries are represented. Income categories per World Bank List of Economies 2005 (7).

 


   DISCUSSION
Top
 Abstract
 Introduction
 METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
We conducted a bibliometric analysis of global clinical research attributed to anesthesia-based researchers and found publications in diverse disciplines reflecting the nature of the specialty itself. Despite being limited to English-language publications, non-English speaking nations contributed strongly to this diversity. We also found that although the overall productivity was highest for the United States, per capita productivity was higher in Western European countries and Japan. Economic development had a significant impact on academic productivity, with higher income nations contributing to a majority of publications.

Previous bibliometric research has concentrated on publications that focus on anesthesia and related subspecialties, such as intensive care (1–4). Specific studies have examined productivity in the field of anesthesia, intensive care, or in specialty-specific journals. Each of these has been limited to research within our specialty. For instance, the Journal Citation Reports from the ISI Web of Knowledge (Thomson Scientific) lists 22 journals under the "anesthesiology" subject category and 18 under the "critical care medicine" category. Bibliometric research using journal-specific or category-specific data would therefore be limited in scope.

Anesthesia as a specialty interacts with many disciplines, including surgery, neurology, cardiology, obstetrics, pulmonology, critical care, and hematology. This enables anesthesiologists to collaborate in clinical research with many disciplines. Consequently, the opportunities for publication extend to a broad range of journals. Therefore, subject-specific searches will likely underestimate the true contribution of anesthesia-based researchers to medical literature. Nevertheless, a majority of the articles were indeed limited to the 17 journals that could be categorized under "anesthesiology."

Several studies have examined international scientific output. Falagas et al. (8) used a metric in which the total number of publications in three broad scientific disciplines was multiplied by the impact factor of the individual journals in each broad category, and then adjusted for the gross domestic product of each region. Based on this metric, Canada had the highest research productivity in most fields, followed by the United States. Similar to our findings, Figueredo et al. (1) evaluated the geographic distribution of publications within the top 10 anesthesiology journals and found a declining United States contribution from 1997 to 2001, and a high per capita productivity in North European nations. Although our study solely examined clinical research independent of cited journal, and was not limited to designated anesthesiology journals, it supports the findings of Figueredo et al.

The United States, Western Europe, and Japan had the highest mean impact factor of their publications, which likely reflects the relatively high caliber of research publications from these countries. Callaham et al. (9) found that impact factor of the original publishing journal was the strongest predictor of subsequent citations of an article per year.

Seven of the 10 most productive countries per capita were from Northern or Western Europe. The high volume of research output by countries in this region has been described before (1,10) and our findings support these previous observations.

Countries categorized by the World Bank as "high income" dominated research productivity, consistent with previous reports linking economic development with scientific output (1,11–14). The paucity of research from developing nations probably reflects a number of factors, including lack of academic infrastructure, absence of research productivity as a metric for career advancement, and insufficient funding.

Our study has limitations related to the search methodology and databases used. We included only English-language publications because English is the language with the widest readership and global reach (15). Despite the expected bias towards English-speaking nations, the contribution of non-English language countries was strong, especially those from Europe. It is also possible that not all publications from anesthesia-based researchers were identified, as some publications only included institutional affiliation and not the author's academic department. We included publications only from 2000 onwards, when electronic submissions in major journals made it easier to track author affiliations. Our study included only clinical research publications, and thus we cannot draw conclusions about basic science publications. Impact factors were available for 415 of the 551 journals in the database, representing 92.4% of all publications.

In summary, we found that clinical research attributable to investigators in our specialty is diverse and extends beyond the traditional field of anesthesia and intensive care. Although the United States leads in academic productivity, per capita scientific output is higher in European nations. Economic development is closely linked to national research productivity with high income nations dominating global clinical research.


   Footnotes
 
Accepted for Publication August 3, 2007.

Supported by intramural funds from the Division of Cardiothoracic Anesthesiology and Critical Care Medicine, Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina.

Conflicts of Interest: None.

Presented in part at the Annual Meeting of the American Society of Anesthesiologists, San Francisco, CA, October 2007.

Reprints will not be available from the author.


   REFERENCES
Top
 Abstract
 Introduction
 METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Figueredo E, Sanchez Perales G, Munoz Blanco F. International publishing in anaesthesia—how do different countries contribute? Acta Anaesthesiol Scand 2003;47:378–82[Web of Science][Medline]
  2. Tsui BC, Li LX, Ma V, Wagner AM, Finucane BT. Declining randomized clinical trials from Canadian anesthesia departments? Can J Anaesth 2006;53:226–35[Web of Science][Medline]
  3. Pua HL, Lerman J, Crawford MW, Wright JG. An evaluation of the quality of clinical trials in anesthesia. Anesthesiology 2001;95:1068–73[Web of Science][Medline]
  4. Lauritsen J, Moller AM. Publications in anesthesia journals: quality and clinical relevance. Anesth Analg 2004;99:1486–91; table of contents
  5. National Library of Medicine: MEDLINE®/PubMed® Data Element (Field) Descriptions. 2007. Available at: http://www.nlm.nih.gov/bsd/mms/medlineelements.html. Accessed on April 5, 2007
  6. Population, Resources, Environment and Development: The 2005 Revision. United Nations Populations Division. 2005. Available at: http://unstats.un.org/pop/dVariables/DRetrieval.aspx. Accessed on March 27, 2007
  7. World Bank List of Economies. World Bank Data Development Group. Washington, DC. 2005. Available at: http://web.worldbank.org/WBSITE/EXTERNAL/DATASTATISTICS/0,contentMDK:20420458~menuPK:64133156~pagePK:64133150~piPK:64133175~theSitePK:239419,00.html. Last accessed March 27, 2007
  8. Falagas ME, Michalopoulos AS, Bliziotis IA, Soteriades ES. A bibliometric analysis by geographic area of published research in several biomedical fields, 1995–2003. CMAJ 2006;175:1389–90[Abstract/Free Full Text]
  9. 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;287:2847–50[Abstract/Free Full Text]
  10. Skram U, Larsen B, Ingwersen P, Viby-Mogensen J. Scandinavian research in anaesthesiology 1981–2000: visibility and impact in EU and world context. Acta Anaesthesiol Scand 2004;48:1006–13[Web of Science][Medline]
  11. Division of Science Resources Statistics NSF. U.S. and international research and development: funds and technology linkages. In: Science and engineering indicators 2004. Arlington, VA: National Science Board, 2004:Chap 4-44-6
  12. Monge-Najera J, Nielsen V. The countries and languages that dominate biological research at the beginning of the 21st century. Rev Biol Trop 2005;53:283–94[Web of Science][Medline]
  13. Michalopoulos A, Falagas ME. A bibliometric analysis of global research production in respiratory medicine. Chest 2005;128:3993–8[Web of Science][Medline]
  14. Rosmarakis ES, Vergidis PI, Soteriades ES, Paraschakis K, Papastamataki PA, Falagas ME. Estimates of global production in cardiovascular diseases research. Int J Cardiol 2005;100:443–9[Web of Science][Medline]
  15. Villar J. English, an international language in medicine. Med Clin (Barc) 1988;91:23–4[Medline]



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Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press