More Neuroscience Research Articles Are Reporting Sex of Research Animals, But Sex Bias Persists
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Material below summarizes the article Problems and Progress Regarding Sex Bias and Omission in Neuroscience Research, published on November 3, 2017, in eNeuro and authored by Tyler R. Will, Stephanie B. Proaño, Anly M. Thomas, Lindsey M. Kunz, Kelly C. Thompson, Laura A. Ginnari, Clay H. Jones, Sarah-Catherine Lucas, Elizabeth M. Reavis, David M. Dorris, and John Meitzen.
This study highlights the complex status of sex omission and bias in neuroscience research and provides useful information for decisions regarding policy enactment and enforcement, scientific culture, and individual action.
Historically, many neuroscience research articles either neglected to report laboratory animal sex (termed sex omission), or favored one sex over another (termed sex bias, in this case male over female). Documentation of this pattern in neuroscience and other disciplines has prompted intense debate and study, including new scientific findings and regulatory policies.
Relevant and high-quality analysis of sex omission and bias in the neuroscience research literature is a crucial component for informed discussion and decision making.
Before our study, the last published review of sex bias and omission in the neuroscience literature did not analyze articles published after 2011. Furthermore, how sex omission and bias varies with animal species and scientific journals has been largely unexplored.
Our study’s goal was to address this knowledge gap by performing the largest ever analysis of sex omission and bias in neuroscience research articles.
We formed a team of 11 trained curators. They evaluated 6,636 neuroscience research articles on studies that used mice and rats that were published from 2010 – 2014 in six journals. The results yielded signs of progress and remaining challenges.
In terms of progress, the proportion of neuroscience research articles failing to document mice and rat sex dropped from roughly 50 percent in 2010 to 20 percent in 2014. Thus, sex omission is decreasing. This represents real and substantial improvement in the documentation of biological sex, which is a critical experimental variable across the nervous system.
On the other hand, sex bias remains present, but it is complex. On one hand, more articles are reporting the use of both males and females, reaching a high of about 35 percent in 2014. However, the substantial majority of these articles do not report assessing sex as an experimental variable at all, independent of whether a sex difference or similarity was detected.
The number of articles on studies using only males remains high and increased to about 40 percent of all articles in 2014. At the same time, the number of articles on studies using only females remained low, comprising about six percent of all articles in 2014. Both sex bias and omission varied considerably by species and journal.
In 2014, over 40 percent of articles on studies using mice reported the use of both males and females. In contrast, only about 20 percent of articles on studies using rats reported the use of both males and females. Almost 60 percent of articles on studies using rats reported the sole use of males. This variation in sex bias and omission also extended across journals, with substantial differences in the proportion of articles not reporting sex remaining present through 2014.
These findings show sex omission is decreasing, although there is still much work to be done to accomplish complete documentation of the sex of animals. Sex bias remains present, but exhibits a complex and changing phenotype.
Bias and omission vary between studies employing mice and rats, making the case for further research into the underlying etiology and whether research using other relevant species demonstrates such divergence. The considerable differences in sex omission across journals indicates editorial policies and enforcement are highly relevant in controlling sex omission, and policy effectiveness should be empirically assessed.
Given the dramatic changes in sex omission and bias detected, future studies should continue to assess and further investigate these phenomena across years. This is especially relevant as multiple journals have adopted new editorial policies since 2014 and as granting agencies such as NIH have introduced regulatory policies such as Sex as a Biological Variable (SABV).
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Problems and Progress Regarding Sex Bias and Omission in Neuroscience Research. Tyler R. Will, Stephanie B. Proaño, Anly M. Thomas, Lindsey M. Kunz, Kelly C. Thompson, Laura A. Ginnari, Clay H. Jones, Sarah-Catherine Lucas, Elizabeth M. Reavis, David M. Dorris, and John Meitzen. eNeuro Nov 2017, 4 (6). DOI: 10.1523/ENEURO.0278-17.2017