Citation by other authors is important in the dissemination of published
science, but factors predicting it are little studied.
To identify characteristics of published research predicting citation
in other journals, we searched the Science Citations Index database for a
standardized 3.5 years for all citations of published articles originally
submitted to a 1991 emergency medicine specialty meeting. Analysis was conducted
by classification and regression trees, a nonparametric modeling technique
of regression trees, to determine the impact of previously determined characteristics
of the full articles on the outcome measures. We calculated the the number
of times an article was cited each year and calculated the mean impact factor
(citations per manuscript per year) in other citing journals.
Of the 493 submitted manuscripts, 204 published articles met entry criteria.
The mean citations per year was 2.04 (95% confidence interval, 1.6-2.4; range,
0-20.9) in 440 different journals. Nineteen articles (9.3%) were never cited.
The ability to predict the citations per year was weak (pseudo R2 = 0.14.). The strongest predictor of citations per year
was the impact factor of the original publishing journal. The presence of
a control group, the subjective newsworthiness score, and sample size predicted
citation frequency (24.3%, 26.0%, and 26.5% as strongly, respectively). The
ability to predict mean impact factor of the citing journals was even weaker
(pseudo R2 = 0.09). The impact factor
of the publishing journal was the strongest predictor, followed by the newsworthiness
score (89.9% as strongly) and a subjective quality score (61.5%). Positive
outcome bias was not evident for either outcome measure.
In this cohort of published research, commonly used measures of study
methodology and design did not predict the frequency of citations or the importance
of citing journals. Positive outcome bias was not evident. The impact factor
of the original publishing journal was more important than any other variable,
suggesting that the journal in which a study is published may be as important
as traditional measures of study quality in ensuring dissemination.