Citations to trials of nicotine replacement therapy were biased toward positive results and high-impact-factor journals.

OBJECTIVE To study variations in the number of times trials of nicotine replacement therapy (NRT) were cited, and which characteristics of trials predicted the number of citations and the impact factors of journals in which articles were published. STUDY DESIGN AND SETTING We used all 105 randomized controlled trials in the Cochrane review of NRT for smoking cessation. We obtained impact factors from the Journal Citation Reports and the number of citations from ISI Web of Knowledge and Google Scholar. RESULTS Trials were cited from 0 to 632 times (median 23 times). Trials were cited more often when results were statistically significant than when they were not (median=41 vs. 17 times, P<0.001), and when impact factors were higher (10.2 more citations per impact factor point, P<0.001). Patch trials were cited more often than gum trials (median=29 vs. 17 times, P=0.001), and trials funded by the pharmaceutical industry were cited more often than other trials (median=28 vs. 16.5 times, P=0.001). Trials with statistically significant results were published in journals with higher impact factors than trials with nonsignificant results (median impact factor=2.80 vs. 1.81, P=0.011). CONCLUSION Citations were biased toward trials with positive results and toward trials published in high-impact-factor journals.

[1]  J. Lafitte,et al.  Citation indexes do not reflect methodological quality in lung cancer randomised trials. , 2003, Annals of oncology : official journal of the European Society for Medical Oncology.

[2]  Vwani P. Roychowdhury,et al.  Read Before You Cite! , 2003, Complex Syst..

[3]  Andy R Weale,et al.  The level of non-citation of articles within a journal as a measure of quality: a comparison to the impact factor , 2004, BMC medical research methodology.

[4]  P. Seglen,et al.  Citations and journal impact factors: questionable indicators of research quality , 1997, Allergy.

[5]  Michael Mabe,et al.  Growth dynamics of scholarly and scientific journals , 2001, Scientometrics.

[6]  Mike Thelwall,et al.  Sources of Google Scholar citations outside the Science Citation Index: A comparison between four science disciplines , 2008, Scientometrics.

[7]  J. Gerberding,et al.  Actual causes of death in the United States, 2000. , 2004, JAMA.

[8]  E. Garfield.  The history and meaning of the journal impact factor. , 2006, JAMA.

[9]  M. Tansella,et al.  Validity of the impact factor of journals as a measure of randomized controlled trial quality. , 2006, Journal of Clinical Psychiatry.

[10]  Jean-François Etter,et al.  The impact of pharmaceutical company funding on results of randomized trials of nicotine replacement therapy for smoking cessation: a meta-analysis. , 2007, Addiction.

[11]  E. Gallagher,et al.  Evidence of methodologic bias in the derivation of the Science Citation Index impact factor. , 1998, Annals of emergency medicine.

[12]  Marc Luwel,et al.  Is the science citation index US-biased? , 1999, Scientometrics.

[13]  Robert West,et al.  What do citation counts count for in the field of addiction? An empirical evaluation of citation counts and their link with peer ratings of quality. , 2002, Addiction.

[14]  E. Garfield.  Fortnightly Review: How can impact factors be improved? , 1996 .

[15]  Jean-François Etter,et al.  Nicotine replacement therapy for long-term smoking cessation: a meta-analysis , 2006, Tobacco Control.

[16]  Harlan M Krumholz,et al.  Guest authorship and ghostwriting in publications related to rofecoxib: a case study of industry documents from rofecoxib litigation. , 2008, JAMA.

[17]  J. Ioannidis,et al.  Relative Citation Impact of Various Study Designs in the Health Sciences , 2005, JAMA.

[18]  Aker,et al.  A controlled trial of sustained-release bupropion, a nicotine patch, or both for smoking cessation. , 1999, The New England journal of medicine.

[19]  R. Wears,et al.  Journal prestige, publication bias, and other characteristics associated with citation of published studies in peer-reviewed journals. , 2002, JAMA.

[20]  R. Perera,et al.  Nicotine replacement therapy for smoking cessation. , 2012, The Cochrane database of systematic reviews.

[21]  C. Gluud,et al.  Citation bias of hepato-biliary randomized clinical trials. , 2002, Journal of clinical epidemiology.

[22]  McGinnis Jm,et al.  Actual causes of death in the United States. , 1993 .

[23]  P. Seglen,et al.  Education and debate , 1999, The Ethics of Public Health.

[24]  G. O. Lignac.  [Actual causes of death]. , 1951, Nederlands tijdschrift voor geneeskunde.

[25]  G Walter,et al.  The Impact Factor: Time for Change , 2001, The Australian and New Zealand journal of psychiatry.

[26]  Martin Schumacher,et al.  The relationship between quality of research and citation frequency , 2006, BMC medical research methodology.

[27]  M. V. Simkin,et al.  Copied citations create renowned papers , 2003, cond-mat/0305150.

[28]  A. Paraskeva,et al.  Self-citations in six anaesthesia journals and their significance in determining the impact factor. , 2000, British journal of anaesthesia.

[29]  J. Ioannidis.  Contradicted and initially stronger effects in highly cited clinical research. , 2005, JAMA.

[30]  P. Jacsó.  As we may search : Comparison of major features of the Web of Science, Scopus, and Google Scholar citation-based and citation-enhanced databases , 2005 .

[31]  T. Opthof,et al.  Sense and nonsense about the impact factor. , 1997, Cardiovascular research.

[32]  M. Swiontkowski,et al.  Factors associated with citation rates in the orthopedic literature. , 2007, Canadian journal of surgery. Journal canadien de chirurgie.

[33]  Ruben Coronel,et al.  Impact factors: no totum pro parte by skewness of citation. , 2004, Cardiovascular research.