Impact factor and electronic versions of biomedical scientific journals

Background and Objectives. The development of electronic editions of scient ific journals and the rapid spread of scientific information might modify t he pattern the bibliographic citations, and thus the impact factor and qual ity of journals. We assessed changes in the impact factor over years of a n umber of journals and whether the presence of an electronic version of the journal was associated with the impact factor score. Design and Methods. This is a retrospective longitudinal study. The availab ility of journals (table of contents (TOC), abstracts, full text and free f ull text) on Internet, in years 1995-2000, was assessed between December 20 00 and January 2001. The first 20 top-journals from 8 subject categories we re included. Changes in impact factor overtime and association with Interne t availability were modeled. Results. Overall, 118/139 journals (85%) had their TOC on the Internet, of these 107 (77%) had abstracts, 97 (70%) had full text and 33 (24%) free ful l text. The median impact factor for all journals was 1.65, 2.08, 2.10, 2.2 1 and 2.35 for the years from 1995 to 1999, respectively. This increase was statistically significant, with differences among subject categories. The presence of TOC, abstracts and full text on the Internet was also significa ntly associated with higher impact factor, after accounting for time and su bject category. Interpretation and Conclusions. The impact factor has been used for assessi ng the quality of journals. We identified a new limitation of this indicato r: the impact factor seems to be related to the amount of circulation of in formation through Internet. This could be a temporary limitation, associate d with diffusion of journals on, and spread of Internet. (C) 2001, Ferrata Storti Foundation.