Significant changes in authorship patterns and characteristics of articles were observed from 1989 to 2009. We found an increase in the number of authors per article over time, with fewer single-author papers now published. The explanations for the changes are likely multifactorial, including increased pressure to publish, increased research complexity, and inappropriate authorship. To prevent inappropriate author-number inflation and to preserve authorship's meaning and value, authors should adhere to the criteria for authorship from the International Committee of Medical Journal Editors.