Levels of Evidence in the Clinical Sports Medicine Literature

Abstract

Background: There has been an increased emphasis on improving the level of evidence used as the basis for clinical treatment decisions. Several journals now require a statement of the level of evidence as a basic gauge of the study’s strength. Purpose: To review the levels of evidence in published articles in the clinical sports medicine literature and to determine if there has been an improvement in the levels of evidence published over the past 15 years. Study Design: Systematic review. Methods: All articles from the years 1995, 2000, 2005, and 2010 in The American Journal of Sports Medicine ( AJSM), Arthroscopy, and sports medicine–related articles from The Journal of Bone and Joint Surgery–American ( JBJS-A) were analyzed. Articles were categorized by type and ranked for level of evidence according to guidelines from the Centre for Evidence-Based Medicine. Excluded were animal, cadaveric, and basic science articles; editorials; surveys; special topics; letters to the editor; and correspondence. Statistical analysis was performed with chi-square. Results: A total of 1580 articles over the 4 periods met the inclusion criteria. The percentage of level 1 and 2 studies increased from 6.8% to 12.6%, 22.9%, and 23.5%, respectively ( P < .0001), while level 4 and 5 studies decreased from 78.9% to 72.4%, 63.9%, and 53.0% ( P < .0001). JBJS-A had a significant increase in level 1 and 2 studies (4.1%, 5.1%, 28.2%, 27.8%; P < .0001), as did AJSM (9.4%, 17.1%, 36.1%, 30.1%; P < .0001). Arthroscopy showed no significant change over time. Diagnostic, therapeutic, and prognostic studies all showed significant increases in level 1 and 2 studies over time ( P < .05). Conclusion: There has been a statistically significant increase in the percentage of level 1 and 2 studies published in the sports medicine literature over the past 15 years, particularly in JBJS-A and AJSM. The largest increase was seen in diagnostic studies, while therapeutic and prognostic studies demonstrated modest improvement. The emphasis on increasing levels of evidence to guide treatment decisions for sports medicine patients may be taking effect.