Sex-specific analysis of data in high-impact orthopaedic journals: how are we doing?

In 2001, the Institute of Medicine released a report stating that sex must be considered in all aspects and at all levels of biomedical research. Knowledge of differences between males and females in responses to treatment serves to improve our ability to care for our patients.

The purpose of our study was to determine (1) if there is an increase in the proportion of sex-specific reporting from 2000 to 2005 and to 2010; and (2) whether there is a proportional difference in such reporting based on journal type: subspecialty versus general orthopaedics. We hypothesize that assessment of the role of sex in outcomes has improved during the past 15 years and that the proportion of studies with of sex-specific analyses has increased with awareness of the role of sex in clinical outcomes and disease states. We additionally hypothesized that the reporting of sex would be similar between subspecialty and general orthopaedic journals.

Five high-impact orthopaedic journals, consisting of two general and three subspecialty journals, were chosen for review. Issues from even-numbered months during three calendar years (2000, 2005, 2010) were critically assessed for the presence of sex-specific analyses and reporting by two separate reviewers. Retrospective and prospective clinical studies, with a minimum of 20 patients, were included for analysis. Cadaveric, biomechanical, and in vitro studies were excluded. Review articles and clinical studies with less than 20 patients were excluded. A total of 821 studies that met inclusion criteria were analyzed: 206 in 2000, 277 in 2005, and 338 in 2010.

Overall, the proportion of sex-specific analyses increased during the three times studied (19%, 40/206, [95% CI, 0.14-0.25] of the studies in 2000; 27%, 77/277, [95% CI, 0.23-0.33] in 2005; and 30%, 102/338, [95% CI, 0.25-0.35] in 2010). The increase in the proportion of sex-specific analysis was significant between 2000 and 2005 (p = 0.033), but was not significant between 2005 and 2010 (p = 0.518). During each of the three specific years studied, general and subspecialty journals increased in the proportions that reported sex-based analyses, but specialty journals had significantly higher reporting rates only in 2000 (2000: 11.9%, 13/109, [95% CI, 0.06-0.18] and 27.8%, 27/97, [95% CI, 0.19-0.37], p = 0.004; 2005: 22.9%, 33/144, [95% CI, 0.16-0.30], and 33.1%, 44/133, [95% CI, 0.25-0.41], p = 0.059; 2010: 28.2%, 51/181, [95% CI, 0.22-0.35] and 32.5%, 51/157, [95% CI, 0.25-0.40], p = 0.390).

Our findings indicate that inclusion of sex-specific analysis and reporting in the orthopaedic literature improved during our study period, but are present in less than 1/3 of the studies. Although subgroup analysis and reporting are required by NIH guidelines, it is important that such analyses be published in non-NIH-funded studies to generate hypotheses regarding sex differences for subsequent research. These data also are important as they can be used in systematic reviews where large independent studies may not be available in the literature.

Where evaluating conditions that affect males and females, studies should be designed with sufficient sample size to allow for subgroup analysis by sex to be performed, and they should include sex-specific differences among the a priori research questions.