Objective: The development of evidence-based medicine has contributed to improved patient outcomes. This study aims to identify the trends in levels of evidence in otolaryngology journals over time, as represented by the 4 most widely circulated peer-reviewed otolaryngology journals.
Methods: A review of all articles from 2007, 2010, 2013, 2016, and 2019, in 4 major otolaryngology journals. Data points included journal source, year of publication, country of origin, first author sex, and subspecialty category within otolaryngology. Level of evidence was determined based on the study's primary research question and was graded on a scale of 1 (strongest) to 4 (weakest) based on the Oxford Centre of Evidence-based Medicine - Levels of Evidence guideline. Comparison of levels of evidence was performed using Kruskal-Wallis analysis of variance for ordinal data.
Results: About 4297 articles were identified over 12 years. The number of research articles remained consistent over the 12 years of this study. Clinical research increased from 78.6% to 85.1%. Female first authorship increased from 20.3% in 2007 to 31.0% in 2019. Of 3558 articles that constituted clinical research from 2007 to 2019, level 1 studies increased from 0.9% to 3.6%, with level 4 studies remaining stable at an overall rate of 60.3%. Randomized controlled trials remained stable at 4.6% of all studies. Systematic reviews increased from 3.2% to 8.4%.
Conclusion: This article provides an update on the levels of evidence to allow for an honest self-assessment of otolaryngology as a scientific field.
Keywords: evidence-based medicine; levels of evidence; randomized controlled trials; research.