The effect of online status on the impact factors of general internal medicine journals

Background: We sought to determine the effects of becoming available online on impact factors of general medicine journals. Methods: Through MEDLINE with an institutional subscription, the 2004 online status of "Medicine, General and Internal" journals listed in the Institute for Scientific Information (ISI) Journal Citation Reports (JCR) was classified as full text on the Net (FUTON), abstract only, or no abstract available (NAA)/unavailable in MEDLINE. Similarly, through use of a home computer without an institutional subscription, the 2004 online status of the same journals was determined. For each journal, impact factors for 1992 to 2003 were obtained. Results: Of the 102 "Medicine, General and Internal" journals listed in the ISI JCR, 71 (70%) existed in both pre-Internet (1992) and Internet (2003) eras. Of these 71 journals, those available as FUTON in 2004 had higher median impact factors than non-FUTON journals in 1992 (p<0.0001) and 2003 (p<0.0001). Journals that became available online, at least partially, had significant increases in median impact factors from 1992 to 2003 (p<0.0001 for journals that became available as FUTON and for journals that provided an abstract only). However, journals that became available as FUTON had a greater increase in median impact factor from 1992 to 2003 than other journals (p=0.002). Similar results were obtained using impact factor data according to journal online status through use of a home computer without an institutional subscription and for English-language journals only. Conclusion: Becoming available online as FUTON is associated with a significant increase in journal impact factor.