title: Time trends in the impact factor of Public Health journals.
abstract: BACKGROUND
  Journal impact factor (IF) is linked to the probability of a paper being cited and is progressively becoming incorporated into researchers' curricula vitae. Furthermore, the decision as to which journal a given study should be submitted, may well be based on the trend in the journal's overall quality. This study sought to assess time trends in journal IF in the field of public, environmental and occupational health.
  
  
  METHODS
  We used the IFs of 80 Public Health journals that were registered by the Science Citation Index from 1992 through 2003 and had been listed for a minimum period of the previous 3 years. Impact factor time trends were assessed using a linear regression model, in which the dependent variable was IF and the independent variable, the year. The slope of the model and its statistical significance were taken as the indicator of annual change.
  
  
  RESULTS
  The IF range for the journals covered went from 0.18 to 5.2 in 2003. Although there was no statistical association between annual change and mean IF, most of the fastest growing journals registered mean IFs in excess of 1.5, and some represented emerging areas of public health research. Graphs displaying IF trends are shown.
  
  
  CONCLUSIONS
  In view of the delay between the publication of IFs and that of any given paper, knowing the trend in IF is essential in order to make a correct choice of journal.
authors.affiliation: National Center for Epidemiology, Carlos III Institute of Health, Sinesio Delgado 6, 28029 Madrid, Spain. glabente@isciii.es
authors.forename: Gonzalo
authors.initials: G
authors.lastname: López-Abente
authors.forename: Concha
authors.initials: C
authors.lastname: Muñoz-Tinoco
mesh_terms: D015706:Bibliometrics; D016206:Databases, Bibliographic / Q000706:statistics & numerical data*; D003657:Decision Making; D006801:Humans; D015233:Models, Statistical; D010506:Periodicals as Topic / Q000145:classification / Q000706:statistics & numerical data*; D011634:Public Health; D011643:Publishing / Q000706:statistics & numerical data; D012106:Research / Q000706:statistics & numerical data*; D013997:Time Factors