Open access to journal articles in oncology: current situation and citation impact

Recent years have seen numerous efforts and resources devoted to the development of open access (OA), but the current OA situation of the oncology literature remains unknown. We conducted this cross-sectional study to determine the current share and provision methods of OA in the field of oncology, identify predictors of OA status (OA versus non-OA), and study the association between OA and citation counts.

PubMed was searched for oncology-related, peer-reviewed journal articles published in December 2014. Google, Google Scholar, PubMed, ResearchGate, OpenDOAR and OAIster were manually checked to assess the OA status of each included article. Citation data were extracted from Web of Science, Scopus and Google Scholar. Descriptive statistics were used to summarize the OA proportion (primary outcome) and OA provision methods. Multivariable logistic regression and multilevel generalized linear model analyses were performed to study predictors of OA status and the association between OA and citation counts, respectively.

In a random sample of 1000 articles, 912 were deemed eligible and therefore included. Of these, the full-texts of 530 articles (58.1%; 95% CI: 54.9-61.3) were freely available online: 314 (34.4%) were available from publishers ('Gold road' to OA), 424 (46.5%) were available via self-archiving ('Green road' to OA). According to multivariable regression analyses, impact factor, publisher type, language, research type, number of authors, continent of origin, and country income were significant predictors of articles' OA status; OA articles received a citation rate 1.24 times the incidence rate for non-OA articles (95% CI: 1.05-1.47; P = 0.012).

Based on our sample, in the field of oncology, 42% of recent journal articles are behind the pay-wall (non-OA) 1 year after publication; the 'Green road' of providing OA is more common than the 'Gold road'; OA is associated with higher citation counts.