To the Editor: Impact factors of medical journals
are calculated as the total number of current citations of articles published
in a journal during the previous 2 calendar years divided by the total number
of designated articles published in that journal during the same period.1 Thus, impact factors indicate the annual average
number of citations of articles that have appeared in a given journal.
Nakayama T, Fukui T, Fukuhara S, Tsutani K, Yamazaki S. Comparison Between Impact Factors and Citations in Evidence-Based Practice Guidelines. JAMA. 2003;290(6):755–756. doi:10.1001/jama.290.6.755-a