As Richard Horton reminded me this morning over breakfa…sorry, I’m still in #johannhari mode. In this week’s Lancet Editorial, Richard Horton name drops the just-published 2010 Journal Citation Report Impact Factors. Hotter than a hot cross bun, the Journal Citation Index (accessible via your university or public library) provides a measure of the frequency with which an average article is cited each year in the 2 years after publication.

For any journal to have an Impact Factor, however, it must be tracked by Thomson Reuters (ISI) for three years.  This means that very new journals (such as so-called ‘open access’ journals) won’t yet have an impact factor.

If you want to get into a scrap with a bitter academic (or fascist dictator) facing their umpteenth rejection from their pet ‘respected journal’, mention impact factors. Measuring impact, as we all know, is a contentious issue, and this is the case with journals as much as it is for health interventions.

Quality

Because a journal’s impact factor is derived from citations to all articles in a journal, this number cannot tell us anything about the quality of any specific research article in that journal, nor of the quality of the work of any specific author. These points become particularly evident by understanding that a journal’s impact factor can be substantially affected by the publication of review articles (which usually acquire more citations than research articles) or the publication of just a few very highly cited research papers.

Influence

Moreover, a journal’s impact factor says nothing at all about how well read and discussed the journal is outside the core scientific community or whether it influences health policy. For a journal such as PLoS Medicine, which strives to make our open-access content reach the widest possible audience—such as patients, health policy makers, non-governmental organizations, and school-teachers—impact factor is a poor measure of overall impact.

Having said all that, I was curious to know how my favourite global public health journals perform in the latest Index. How did your favourite do?

Journal Impact Factor (JCI, Reuters 2011)
African Journal of AIDS Research 0.425
AIDS 6.348
AIDS and Behavior 3.195*
American Journal of Public Health 3.85 (4.371*)
BMC Health Services Research 1.72
BMC Public Health 2.364
BMJ 13.471
Bulletin of the WHO 5.459
Globalization and Health 2.07**
Health Affairs 3.792
Health Policy 1.383
Health Policy and Planning 2.793
Health Promotion International 1.544*
Health Research Policy and Systems 1.40**
Health Services Research 2.293
Human Resources for Health 1.38
International Affairs 1.22*
JAIDS 4.57*
Journal of Public Health Policy 1.635
JAMA 30.01
Lancet 33.63
New England Journal of Medicine 53.48
PLoS Medicine 15.61
Public Health 1.267
Social Science and Medicine 2.742*
Transactions of the Royal Society of Tropical Medicine and Hygiene 2.615*
Tropical Medicine and International Health 2.84

* Data from journal website
** Unofficial impact factor

Andrew Harmer