Eysenbach, G (Eysenbach, Gunther) Citation advantage of open access articles PLOS BIOLOGY, 4 (5): 692-698 MAY 2006

[Eugene Garfield]

E-mail Address: geysenba at uhnres.utoronto.ca 

Author(s): Eysenbach, G (Eysenbach, Gunther) 

Title: Citation advantage of open access articles 

Source: PLOS BIOLOGY, 4 (5): 692-698 MAY 2006 

Language: English 

Document Type: Article 

Keywords Plus: IMPACT; PNAS 

Abstract: Open access (OA) to the research literature has the potential to 
accelerate recognition and dissemination of research findings, but its 
actual effects are controversial. This was a longitudinal bibliometric 
analysis of a cohort of OA and non-OA articles published between June 8, 
2004, and December 20, 2004, in the same journal (PNAS: Proceedings of the 
National Academy of Sciences). Article characteristics were extracted, and 
citation data were compared between the two groups at three different 
points in time: at "quasi-baseline" (December 2004,0-6 mo after 
publication), in April 2005 (410 mo after publication), and in October 
2005 (10-16 mo after publication). Potentially confounding variables, 
including number of authors, authors' lifetime publication count and 
impact, submission track, country of corresponding author, funding 
organization, and discipline, were adjusted for in logistic and linear 
multiple regression models. A total of 1,492 original research articles 
were analyzed: 212 (14.2% of all articles) were OA articles paid by the 
author, and 1,280 (85.8%) were non-OA articles. In April 2005 (mean 206 d 
after publication), 627 (49.0%) of the non-OA articles versus 78 (36.8%) 
of the OA articles were not cited (relative risk = 1.3 [95% Confidence 
Interval: 1.1-1.6]; p = 0.001). 6 mo later (mean 288 d after publication), 
non-OA articles were still more likely to be uncited (non-OA: 172 [13.6%], 
OA: 11 [5.2%]; relative risk = 2.6 [1.4-4.7]; p < 0.001). The average 
number of citations of OA articles was higher compared to non-OA articles 
(April 2005: 1.5 [SD = 2.5] versus 1.2 [SD =2.0]; Z = 3.123; p = 0.002; 
October 2005: 6.4 [SD = 10.4] versus 4.5 [SD = 4.9]; Z = 4.058; p < 
0.001). In a logistic regression model, controlling for potential 
confounders, OA articles compared to non-OA articles remained twice as 
likely to be cited (odds ratio = 2.1 [1.5-2.9]) in the first 4-10 mo after 
publication (April 2005), with the odds ratio increasing to 2.9 (1.5-5.5) 
10-16 mo after publication (October 2005). Articles published as an 
immediate OA article on the journal site have higher impact than self-
archived or otherwise openly accessible CIA articles. We found strong 
evidence that, even in a journal that is widely available in research 
libraries, OA articles are more immediately recognized and cited by peers 
than non-OA articles published in the same journal. OA is likely to 
benefit science by accelerating dissemination and uptake of research 
findings. 

Addresses: Univ Hlth Network, Ctr Global eHealth Innovat, Toronto, ON, 
Canada; Univ Toronto, Dept Hlth Policy Management & Evaluat, Toronto, ON, 
Canada 

Reprint Address: Eysenbach, G, Univ Hlth Network, Ctr Global eHealth 
Innovat, Toronto, ON, Canada.
 
E-mail Address: geysenba at uhnres.utoronto.ca 

Cited Reference Count: 17 

Times Cited: 35 

Publisher: PUBLIC LIBRARY SCIENCE 

Publisher Address: 185 BERRY ST, STE 1300, SAN FRANCISCO, CA 94107 USA 

ISSN: 1544-9173 

DOI: 10.1371/journal.pbio.0040157 

29-char Source Abbrev.: PLOS BIOL 

ISO Source Abbrev.: PLoS. Biol. 

Source Item Page Count: 7 

Subject Category: Biochemistry & Molecular Biology; Biology 

ISI Document Delivery No.: 048SN 

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