A controlled analysis of authorship trends over two decades, ,

Objective: The purpose was to assess authorship trends over time by taking account of publication type and controlling for number of investigating centers and funding status in a multivariable analysis. Study Design: A database of 403 randomized studies and 193 controlled observational studies was assembled by means of a combination of electronic and hand search of 4 generic obstetrics and gynecology journals for the years 1975, 1980, 1985, 1990, and 1995. A multivariable logistic regression model was built for evaluating the effect of time on authorship with multiauthored articles as the binary outcome variable (articles were classified as either those with <6 authors or those with ≥6). The analysis was performed separately for the 2 types of publications, and it was adjusted for the confounding effects of number of centers, funding status, and journal of publication. The β coefficient (and its exponent) associated with the time term in the logistic model provided a measure of the trend in publication of multiauthored articles. Results: In randomized studies the odds of publishing a multiauthored article, given the number of centers, funding status, and journal, were increased on average by 6% with every 5-year increment in time (odds ratio, 1.06; 95% confidence interval, 1.02-1.10; P = .007). Similarly, in controlled observational studies, there was a 10% increase in the odds of publishing multiauthored articles (odds ratio, 1.10; 95% confidence interval, 1.01-1.20; P = .03). Conclusion: There is an inflationary trend in authorship that is not explained solely by the increased collaboration between centers and funding for research. (Am J Obstet Gynecol 1999;181:503-7.)