Scientific research on the pineal gland and melatonin: a bibliometric study for the period 1966-1994

By means of teledischarge techniques from the database MEDLINE we selected those documents that contained in their title one or several of the following descriptors: pineal*, epiphys*, or melatonin*, in addition to the descriptor pineal-body in the MESH (Medical Subject Headings) section. A total of 7,617 original documents published between 1966 and 1994 were extracted that dealt with any aspect related with the pineal gland or its main secretary product, melatonin. The main bibliometric laws were applied: Price's Law on the increase in scientific literature, Bradford's Law on the dispersion of the scientific literature, and Lotka's Law on the author's productivity. Furthermore, we have analyzed the participation index (PaI) of the main countries within the global production, the productivity index of the authors (PI), and the number of authors/paper index. Our results demonstrate an exponential increase of the scientific literature on the pineal gland ("r" value = 0.983, in contrast with a "r" value = 0.966 after the linear adjustment). The number of publications on melatonin was less than those on other aspects of pineal research until 1991, when this situation was reversed. The journal with the largest number of original papers is Journal of Pineal Research (1st Bradford's zone) with 533 articles, followed by Journal of Neural Transmission (258) and Neuroendocrinology (221), which constituted the 2nd Bradford's zone. The total number of authors is 9,140, responsible for 23,524 authorships. 3.8% of the authors present a PI > or = 1 (large producers), and 64.9% a PI = 0 (occasional authors). Lotka's Law was widely fulfilled in this material since 10.3% of the authors are responsible of 50.2% of all the papers. The average number of authors per paper has changed from 2.29 in 1966 to 3.85 in 1994. The most productive country (during the interval between 1988-1994) was USA (PaI = 30.6), followed by Japan (7.15), United Kingdom (6.45), Germany (6.37), France (6.26), Italy (6.15) and Spain (5.34). Of the total number articles published, 86.9% are in English.