[Insight-developers] Citation Advantage of Open Access Articles

[Luis Ibanez]

http://biology.plosjournals.org/perlserv/?request=get-document&doi=10%2E1371%2Fjournal%2Epbio%2E0040157

"Citation Advantage of Open Access Articles"

Gunther Eysenbach1

1 Centre for Global eHealth Innovation, University Health Network; and
Department of Health Policy, Management and Evaluation, University of
Toronto, Toronto, Ontario, Canada

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 (4–10 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 OA 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.