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RESEARCH: T Jefferson, C Di Pietrantonj, M G Debalini, A Rivetti, and V Demicheli Relation of study quality, concordance, take home message, funding, and impact in studies of influenza vaccines: systematic review BMJ 2009; 338: b354 [Abstract] [Full text]

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Funding Source and Impact Factor in Trials of Nicotine Replacement Therapy.

Marcus R. Munafo, Robert I. Shortman   (20 February 2009)

Funding Source and Impact Factor in Trials of Nicotine Replacement Therapy. 20 February 2009
Marcus R. Munafo, Reader in Biological Psychology University of Bristol BS8 1TU, Robert I. Shortman Send response to journal: Re: Funding Source and Impact Factor in Trials of Nicotine Replacement Therapy.	The degree to which source of funding plays a role in the publication of scientific research is now well-established. This was elegantly demonstrated in the context of nicotine replacement therapy for smoking cessation by Etter and colleagues (1). They showed evidence of possible publication bias among studies funded by the pharmaceutical industry, but not among studies funded from other sources, and that the former tended to report larger effect size estimates than the latter. Moreover, when the pooled effect size estimate was corrected for this potential bias, the pooled effect size across the two groups of studies became identical. We were motivated by the study of Jefferson and colleagues to re- analyse the data reported by Etter and colleagues to investigate the role of journal Impact Factor. Of the 90 studies included in the original report (1), we were able to extract Impact Factor information for k = 79 studies. Studies funded by the pharmaceutical industry were published in journals with a higher Impact Factor (median 4) than those funded by other sources (median 3), and a Mann-Whitney U-test indicated that this difference was statistically significant (p = 0.007). Moreover, the effect size reported in an individual study was positively correlated with the Impact Factor of the journal within which it was published (Spearman's r = +0.32, p = 0.004). It is worth noting, however, that the relationship between effect size and Impact Factor may extend beyond studies funded by the pharmaceutical industry. We recently reported evidence from genetic association studies that the degree to which an individual study over- estimated the likely true effect size correlated with the Impact Factor of the journal in which it was published (2), as well as the geographical region from which the study originated (3). Our conclusion is that certain features of the scientific environment may influence the apparent strength of evidence for reported relationships, and this itself is an important area for future research. References 1. Etter JF, Burri M, Stapleton J. The impact of pharmaceutical company funding on results of randomized trials of nicotine replacement therapy for smoking cessation: a meta-analysis. Addiction 2007;102(5):815- 22. 2. Munafo MR, Stothart G, Flint J. Bias in genetic association studies and impact factor. Mol Psychiatry 2009;14(2):119-20. 3. Munafo MR, Attwood AS, Flint J. Bias in genetic association studies: effects of research location and resources. Psychol Med 2008;38(8):1213-4. Competing interests: MM has received nicotine replacement products from GlaxoSmithKline and Pfizer for distribution to study participants. He has received consulting fees from the European Commission, the National Audit Office, the American Institutes for Research and G-Nostics Ltd, and honoraria for invited lectures from GlaxoSmithKline, Novartis and Sepracor. RS has no conflicts of interest to declare.