Competing interests at medical journals: industry sponsored trials boost impact factors

These days medical journals are rigorous when it comes to getting researchers to declare any associations with industry that might influence how a trial is reported. Before agreeing to publish a paper, many of the top medical journals require authors to sign a comprehensive conflicts of interest form that outlines any financial or personal relationships that could be perceived as inappropriately influencing the authors’ actions with regard to the research.

But what about the journals themselves, how do they fare when subjected to the same rigorous transparency they impose on their authors? Not too well according to a study published recently in PLoS Medicine. Industry supported trials published in six major medical journals were cited more often than trials not sponsored by industry, and had a considerable bolstering effect on the journals’ impact factors – a measure of the “importance” of a journal.

The authors of this study looked at 1,353 randomised controlled trials published in six general medical journals in 1996-7 and 2005-6: Annals of Internal Medicine, Archives of Internal Medicine, BMJ, Journal of the American Medical Association, Lancet, and New England Journal of Medicine. When they categorised these trials they found that a third (32%) of trials published in NEJM in 1996-7 were industry sponsored, compared with roughly one in 10 (13%) published in BMJ. These proportions dropped for all journals by 2005-6 except for NEJM, so the same proportions nine years later were 32% and 7%.

They then looked at citations for these trials, in 1998 for the 651 published 1996-7 and in 2007 for the 702 from 2005-6. For all journals, there was a significant association between the degree of industry support among the studies published in 2005-6 and the number of citations. This was most pronounced for Annals, Archives, and Lancet, where industry sponsored trials were cited more than twice as often as trials not supported by industry.
Citations are important because they indicate how much a paper has affected a field – the more it has been cited by other authors, the more it has influenced research in the field. Having a high number of citations thus reflects well on the journal that published the study, suggesting that it is featuring the most important research.

The authors then calculated approximate impact factors for the journals by dividing the number of citations by the number of trials published in order to figure out how often the “average” article would be cited. When they removed industry sponsored trials from these equations, the impact factors dropped notably, in particular for NEJM (13-15%) and Lancet (6-11%).

Lastly, editors in chief were contacted and asked to provide information on what proportion of the journal’s total income was from sales of advertisements, reprints, and industry supported supplements. Only BMJ and Lancet provided this data.

Almost half (41%) of Lancet‘s income was from article reprints, which are often bought up by drug companies that sponsored a particular trial to promote the efficacy of their product. A further 1% of the journal’s total income was from display adverts. On the other hand, only 3% of the BMJ‘s income was from reprints and 16% was from display adverts. Neither made much money from industry supported supplements.

Then the authors got cunning. To get financial data for the three American journals – Annals, Archives, and NEJM – they dug up publicly available tax information for the journals’ parent companies. The Massachusetts Medical Society, owner of NEJM, earned 23% of its income from adverts, whereas no data was available on reprints and supplements.

For the American Medical Association, publisher of JAMA, 53% of its income was from adverts and 12% from reprints (no data on supplements). Richard Smith, former editor of the BMJ, reported that reprint sales from a single trial may lead to an income of US$1 million for a journal, so the 12% figure for JAMA is quite noteworthy. The Internal Revenue Service data did not specify the income for the American College of Physicians, publisher of Annals.

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So what do all these findings mean? It seems that publishing industry sponsored trials boosts the reputation of journals, some more than others. Of course, it is important that industry data does get published rather than sit in a drawer somewhere, and it seems a bit misplaced to criticise journals for benefiting from this process. Instead perhaps journals should make clear to what degree they benefit from publishing industry supported trials – financially and status wise.


Lundh A et al. (2010) Conflicts of Interest at Medical Journals: The Influence of Industry-Supported Randomised Trials on Journal Impact Factors and Revenue – Cohort Study. PLoS Medicine 7 (10). DOI: 10.1371/journal.pmed.1000354.

One Response to “Competing interests at medical journals: industry sponsored trials boost impact factors”

  1. Roy Says:

    We are entering an interesting year when links between pharmaceutical companies, politicians, medical journals, the FDA and the medical industry in general are coming more sharply into public focus. With medical doctor Dr Ron Paul gaining ground in the GOP nomination race and Rick Perry already having been brought down by his pharmaceutical contacts in the HPV controversy, the subject has become high profile. Dr Paul recently stated on national TV that there were many pharmacueticals he would not prescribe and that they killed more people than illegal drugs. There should be a lot of truth coming out of the closet in 2011/12, and by 2013 the USA could well have a medical doctor as President.