Importance
Sex is a variable that is poorly controlled for in clinical research.
Objective
Determine if sex bias exists in human surgical clinical research, determine if data are reported and analyzed using sex as an independent variable, and identify specialties where the greatest and least sex biases exist.
Design
Review and data abstraction from published peer-reviewed manuscripts.
Setting
All original peer-reviewed manuscripts published in 2011 and 2012 in Annals of Surgery, American Journal of Surgery, JAMA Surgery, Journal of Surgical Research, and Surgery.
Main Outcome Measures
Study type, location, number and sex of subjects, sex matching, and inclusion of sex-based reporting, statistical analysis, and discussion of data.
Results
Of 2,347 articles reviewed, 1,668 included human subjects. After excluding 365 articles, 1,303 manuscripts remained: 17 (1%) included only males, 41 (3%) included only females, 1,020 (78%) included males and females, and 225 (17%) did not document the sex of the subjects. While females represent over 50% of the total number of subjects included, considerable variability existed with the number of male, female, and unspecified subjects included among the journals, between US domestic and international studies, and between single versus multi-center studies. For manuscripts included in the study, only 38% reported these data by sex, 33% analyzed these data by sex, and 23% included a discussion of sex-based results. Sex matching of the subjects included in the research was poor, with only 18% of the studies matching the inclusion of both sexes by 80%. Upon analysis of the different surgical specialties, a wide variation in sex-based inclusion, matching, and data reporting existed, with colorectal surgery having the best matching of males and females and cardiac surgery having the worst.
Conclusion
Our data show that sex bias exists in human surgical clinical research. Few studies included men and women equally, less than one-third performed data analysis by sex, and there was wide variation in inclusion and matching of the sexes among the specialties and the journals reviewed. Because clinical research serves as the foundation for evidence-based medicine, it is imperative that this disparity be addressed so that therapies benefit both sexes.
