Background: To study different aspects of original articles published in Medicina Clínica (Barcelona) over a 30-year period (1962-1992), with special emphasis on references.
Methods: We selected 12 articles per year at 5-year intervals (1962, 1967, 1972, 1977, 1982, 1987, 1992) using a systematic sampling procedure. The following variables were assessed: number of authors, interval between acceptance of the manuscript and publication in the journal, total number of references, language, document type, and name of the journal.
Results: The mean (+/- standard deviation) number of authors showed a statistically significant increase (ANOVA; F = 13.666; p = 0.0001) from 1.83 +/- 0.71 in 1962 to 6.41 +/- 1.97 in 1992. The interval between acceptance and publication decreased from 315.72 +/- 20.48 days in 1982 to 206.16 +/- 89.23 in 1992 (ANOVA, F = 6.074; p = 0.0058). A total of 1816 references were found (24.2 references per article). English was the language of publication most commonly found (76.76%) followed by Spanish (12.6%). There was a statistically significant increase in the use of references corresponding to English articles over the study period (chi 2 = 314.431; p = 0.0001). A significant change was also observed in the type of document use (chi 2 = 143.996; p = 0.0001); references from journals increased from 73.51% in 1962 to 91.40% in 1992. In addition, 50.46% of the articles were published in only 7.84% of the journals. Eight journals devoted to internal medicine (1.79% of all journals) included 23.46% of the references.
Conclusions: The number of authors has shown a significant increase during the study period. The time elapsed between acceptance and publication has decreased significantly. Spanish authors acquired information mostly from the English literature. Articles published in journals are also mostly used as references. A large percentage of references consisted of articles published in core general journals. These journals accumulate a remarkable percentage of the information.