N. A. Mansukhani1, D. Y. Yoon1, K. A. Teter1, V. C. Stubbs1, T. K. Woodruff2,3, M. R. Kibbe1,2 1Northwestern University,Surgery,Chicago, IL, USA 2Northwestern University,Women’s Health Research Institute,Chicago, IL, USA 3Northwestern University,Obstetrics And Gynecology,Chicago, IL, USA
Introduction: Sex is a highly conserved difference between members of the same species, but is a variable that is poorly controlled in clinical research. The objective of this study is to determine if sex bias exists in human clinical surgical research, and identify areas where the greatest and least sex biases exist. We hypothesize that males and females are not included in surgical clinical research in equal numbers, and that data are not reported or analyzed using sex as an independent variable.
Methods: All manuscripts published in Annals of Surgery, American Journal of Surgery, JAMA Surgery, Journal of Surgical Research, and Surgery in 2011 and 2012 were reviewed. Data abstracted included study type, location, number and sex of the subjects, the degree of 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. Of these, an additional 365 were excluded on the basis of including animals or cells, studying a sex-specific disease, or not reporting the number of subjects included. Of the remaining 1,303 manuscripts, 17 (1%) were male-only studies, 41 (3%) were female-only studies, 1,020 (78%) included males and females, and 225 (17%) did not document the sex of the subjects studied. Using a liberal 90%, 80%, and 50% criteria for matching inclusion of both sexes, of the manuscripts that included both males and females only 118 (9%), 237 (18%), and 589 (45%) of studies matched the sex of the subjects included. For manuscripts that included both sexes, only 497 (49%) studies reported the data by sex, 432 (42%) analyzed the data by sex, and 299 (29%) included a discussion of sex-based results. Upon analysis of the different surgical specialties, a wide variation in sex-based inclusion, matching, and data reporting existed. Vascular surgery had the most male-only manuscripts (7%), breast surgery had the most female-only manuscripts (59%), surgical oncology included both sexes in the most manuscripts (91%), and breast surgery included both sexes in the least manuscripts (7%). Surgical education documented the sex of subjects in only 53% of publications, whereas thoracic surgery documented the sex of subjects in 95% of publications. Sex-based reporting of data was only performed in 28% of publications in American Journal of Surgery whereas it was performed in 45% of publications in JAMA Surgery.
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 between 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 because therapies and practice derived from such studies may be specific to only one sex.