In order to study conflicts of interest in journals, Lundh et al. (October 2010) chose six high-impact medical journals: Annals of Internal Medicine (Annals), Archives of Internal Medicine (Archives), BMJ, JAMA, The Lancet and NEJM and studied the proportions of industry-supported randomized clinical trials (RCTs). The authors focused on citations from 1996-1997 for 1995 papers and 2007 citations for 2005-2006 RCTs. They categorized funding as industry support, mixed support, nonindustry support and no statement about support.
Then came the tricky part: getting financial data from the journals about their income from advertisements, reprints and industry-supported supplements as percentage of the journals' total income as well as the total number of reprints sold. BMJ and Lancet (British) provided the data, but the other four journals (American) refused to do so. Given that lack of cooperation, the authors had to become creative. The journals' owners are the American College of Physicians (ACP) for Annals, the American Medical Association (AMA) for JAMA and Archives, and the Massachusetts Medical Society (MMS) for NEJM. The authors obtained their publicly available tax forms, that included data on the total income from all types of publishing. The societies, however, publish each more than one journal, so the authors couldn't determine incomes for individual journals. They had to calculate the relative income from industry sources, to which they received confirmation from ACP, but not from AMA and MMS.
In 2005-2006, 32% of the RCTs published in NEJM had industry support. However, for BMJ, only 7% of the RCTs were industry-supported. Declines in proportion of industry-supported trials were statistically significant for Annals and Archives.
Citations and industry support
For 1996-1997 trials, there was a significant correlation between citations and industry support for Lancet and NEJM. The correlation was statistically significant for all journals in 2005-2006. The authors write that "Industry-supported trials published in Annals, Archives and Lancet in 2005-2006 were cited more than twice as often as nonindustry trials and one and a half times more in BMJ, JAMA and NEJM".
The authors calculated the IF of each one of the journals without the industry-supported trials. The NEJM had the largest decrease in IF, followed by the Lancet. The BMJ's IF barely changed.
Implications for mass media reporting
NEJM is the most prestigious medical journal in the world. Moriarty et al. (2010) found that it was the most cited source in news stories about cancer research (see my last post). If a third of the clinical trials published in NEJM are published by the industry, which means they are more likely to have positive results for the funding company (Lexchin et al., 2003), and taking into account that the NEJM is a very popular source of health news, that means the industry doesn't just gain influence with clinicians by publishing in NEJM, but with the general public as well.
See my follow-up post: How JAMA managed to avoid becoming an advertising platform for the pharmaceutical companies
Lexchin, J. (2003). Pharmaceutical industry sponsorship and research outcome and quality: systematic review BMJ, 326 (7400), 1167-1170 DOI: 10.1136/bmj.326.7400.1167
Moriarty CM, Jensen JD, & Stryker JE (2010). Frequently cited sources in cancer news coverage: a content analysis examining the relationship between cancer news content and source citation. Cancer causes & control : CCC, 21 (1), 41-9 PMID: 19784789
Lundh, A., Barbateskovic, M., Hróbjartsson, A., & Gøtzsche, P. (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