Secular trends in impact factor of breastfeeding research publications over a 20-year period

The aim of the current study was to determine whether secular changes have occurred in the breastfeeding literature, in terms of number and type of yearly published articles and impact factor of journals publishing these articles.

In order to evaluate all Medline articles related to breastfeeding, we used the Internet URL www.ncbi.nlm.nih.gov/entrez and searched for articles recorded from January 1, 1992 through December 31, 2011 using as a key word "breast milk," "breast feeding," or "human milk." We specifically studied randomized controlled trials (RCTs), clinical trials, case reports, meta-analyses, letters to the editor, reviews, systematic reviews, practice guidelines, and editorials.

There was a linear increase over the years in all articles recorded, from approximately 1,100/year in 1992 to 2,100/year in 2011 (i.e., an approximately 1.9-fold increase [R(2)=0.995, p=0.001]). Concomitant with the yearly increase in the number of published RCTs per year, there was a linear increase in the number of journals publishing articles on breastfeeding per year (from approximately 20 in 1992 to >60 in 2011 [R(2)=0.811, p<0.001]) but an overall decrease in the average impact factor every year (R(2)=0.202, p=0.047). However, the ratio of high-quality articles selected (RCTs+meta-analyses+systematic reviews+CR)/low-quality articles (reviews+editorials+letters to the editor+case reports) increased significantly over time in favor of the former.

There was a linear increase in the number of publications related to the field of breastfeeding and human milk, and the ratio of high-quality/low-quality articles improved over time, indicating a relative and absolute increase in the number of articles usually considered as being of high quality. There was a significant increase in the number of journals publishing breastfeeding-related articles, with a significant decrease of average impact factor of those journals.