Equal contributions and credit given to authors in anesthesiology journals during a 10-year period

To investigate the prevalence and characteristics of the practice of explicitly giving authors equal credit in publications of major anesthesiology journals. Four major anesthesiology journals (Anesthesia and Analgesia (AA), Anesthesiology, British Journal of Anaesthesia (BJA) and Pain) were searched manually to identify original research articles published between January 1st, 2001 and December 31st, 2010 with respect to equally credited authors (ECAs). It was found that all journals explicitly gave authors equal credit, and articles with ECAs accounted for a greater proportion of the total number of articles published in each journal in 2010 versus that in 2000 (AA: 3.3% vs. 0%; Anesthesiology: 7.1% vs. < 1%; BJA: 5.7% vs. 0%; Pain: 11.0% vs. < 1%). The number of ECAs articles tended to increase significantly yearly in all journals (P < 0.0001 for each journal). The first two authors in the byline received equal credit in most cases. Furthermore, the ECAs articles involved institutions from different countries and regions and were sponsored by various funds. However, no specific guidance concerning this practice was provided in the instructions to authors in the four journals. It is increasingly common to give authors equal credit in original research articles in major anesthesiology journals. Detailed guidelines regarding this practice are warranted in future.