Citation analysis of the ‘big six’ journals in internal medicine

Abstract

Objective: In the field of internal medicine, the classic ‘big six’ (B6) journals are highly valued for the quality and impact of their papers. The B6 include the New England Journal of Medicine (NEJM), the Lancet, Journal of the American Medical Association (JAMA), British Medical Journal (BMJ), Annals of Internal Medicine (AnnIM) and Archives of Internal Medicine (ArchIM). Their high impact is reflected in the omnipresence of citations to B6 papers in medical publications in other journals as well as in the B6 journals themselves. We hypothesized firstly that B6 journals often cite publications from their own journal (autocitations) and secondly that publications from their own journal are cited instead of more recent papers from other journals. This study was performed to evaluate the citing patterns of B6 journals. We evaluated autocitations as well as citations to other B6-journals in terms of frequency and year of publication of the cited papers. Material and methods: Original clinical trials published in B6 journals between January 1st, 2012 and December 31st, 2012 were identified through NCBI Pubmed. Citation lists of these publications were obtained using Thomson Reuters Web of Knowledge. We distinguished three categories: autocitations (citations to papers published in the host journal); B6 citations (citations to papers in B6 journals including autocitations); and other citations (citations to non-B6 journals). Statistics were performed by Chi-square, Kruskal–Wallis and Mann–Whitney U tests using SPSS 17.0. Results: A total of 462 trials were identified with an aggregate of 14,717 citations. Autocitation ranged from 2.5%–1.3% (AnnIM = 2.5%, ArchIM = 4.5%, BMJ = 4.8%, JAMA = 4.8%, Lancet = 6.5%, NEJM = 11.2%). The share of B6 citations ranged from 14.8 to 23% (BMJ = 14.8%, JAMA = 16.4%, AnnIM = 16.9%, Lancet = 19.2%, NEJM = 20.0%, ArchIM = 23.0%). The average proportion of autocitations to B6 citations across the B6 journals was 37.6% varying between 14.8% (AnnIM) and 56.4% (NEJM) (p < .001). Among B6 publications, the median number of autocitations was 2 (IQR = 1–3, p < 0.01) and the median number of B6 citations was 5 (IQR = 3–8, p = 0.42). Autocitations were a median number of 5 years old (IQR = 2–9) which was comparable to non-autocitations except for autocitations in the NEJM which were more recent than other citations (median 4 vs 5 year, p = 0.024). For all journals B6 citations were of comparable publication year as non-B6 citations (median 6 vs 5 years, p = .17). Discussion and conclusion: In the investigated trials the B6 journals differ in their share of autocitations, but all cite the B6 class for a total of nearly 20% of citations. The NEJM is the journal with the highest rate of autocitation. Autocitations or B6 citations were not older or newer than other citations, except for the NEJM in which autocitations are significantly more recent than other citations. The findings might be associated with the ranking of the B6 journals in terms of impact factor.