Policy standpoint: tools to include sex as a variable in biological research

The sex of a person, animal, cell or enzyme is the most powerful variable in health and disease. Yet, even after years of advocacy, only recently has the importance of sex as a biological and experimental variable been addressed1–4. Indeed, the majority of biomedical research is conducted with male animals and cells, neglects to report which sexes were studied or fails to mention if any sex-differences were identified5–6. In addition to being an exclusionary practice, this unidimensional approach to biological processes may be a root cause of the concerns regarding rigour and reproducibility of scientific research7.