The Global Research Collaboration of Network Meta-Analysis: A Social Network Analysis.
OBJECTIVE
Research collaborations in biomedical research have evolved over time. No studies have addressed research collaboration in network meta-analysis (NMA). In this study, we used social network analysis methods to characterize global collaboration patterns of published NMAs over the past decades.


METHODS
PubMed, EMBASE, Web of Science and the Cochrane Library were searched (at 9th July, 2015) to include systematic reviews incorporating NMA. Two reviewers independently selected studies and cross-checked the standardized data. Data was analyzed using Ucinet 6.0 and SPSS 17.0. NetDraw software was used to draw social networks.


RESULTS
771 NMAs published in 336 journals from 3459 authors and 1258 institutions in 49 countries through the period 1997-2015 were included. More than three-quarters (n = 625; 81.06%) of the NMAs were published in the last 5-years. The BMJ (4.93%), Current Medical Research and Opinion (4.67%) and PLOS One (4.02%) were the journals that published the greatest number of NMAs. The UK and the USA (followed by Canada, China, the Netherlands, Italy and Germany) headed the absolute global productivity ranking in number of NMAs. The top 20 authors and institutions with the highest publication rates were identified. Overall, 43 clusters of authors (four major groups: one with 37 members, one with 12 members, one with 11 members and one with 10 members) and 21 clusters of institutions (two major groups: one with 62 members and one with 20 members) were identified. The most prolific authors were affiliated with academic institutions and private consulting firms. 181 consulting firms and pharmaceutical industries (14.39% of institutions) were involved in 199 NMAs (25.81% of total publications). Although there were increases in international and inter-institution collaborations, the research collaboration by authors, institutions and countries were still weak and most collaboration groups were small sizes.


CONCLUSIONS
Scientific production on NMA is increasing worldwide with research leadership of Western countries (most notably, the UK, the USA and Canada). More authors, institutions and nations are becoming involved in research collaborations, but frequently with limited international collaborations.
Department of General Surgery, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.|Evidence-Based Medicine Center, School of Basic Medical Sciences, Lanzhou University, Lanzhou, Gansu, China.
Lun
L
Li
Department of Medicine, University of Valencia/ INCLIVA Health Research Institute and CIBERSAM, Valencia, Spain.|Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada.
Ferrán
F
Catalá-López
Department of History of Science and Documentation, University of Valencia, Valencia, Spain.
Adolfo
A
Alonso-Arroyo
Evidence-Based Medicine Center, School of Basic Medical Sciences, Lanzhou University, Lanzhou, Gansu, China.
Jinhui
J
Tian
Ingenio-Spanish National Research Council (CSIC) and UISYS-University of Valencia, Valencia, Spain.
Rafael
R
Aleixandre-Benavent
Institute for Research in Operative Medicine, Department for Evidence-Based Health Services Research, Witten/Herdecke University, Cologne, Germany.
Dawid
D
Pieper
Evidence-Based Medicine Center, School of Basic Medical Sciences, Lanzhou University, Lanzhou, Gansu, China.
Long
L
Ge
Evidence-Based Medicine Center, School of Basic Medical Sciences, Lanzhou University, Lanzhou, Gansu, China.
Liang
L
Yao
Department of Gastrointestinal Surgery, Xijing Hospital of Digestive Diseases, Xijing Hospital, Four Military Medical University, Xi'an, Shaanxi, China.
Quan
Q
Wang
Evidence-Based Medicine Center, School of Basic Medical Sciences, Lanzhou University, Lanzhou, Gansu, China.
Kehu
K
Yang
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