Elife. 2023 Nov 2;12:e90623. doi: 10.7554/eLife.90623.
To enhance inclusivity and rigor, many funding agencies and journals now mandate the inclusion of females as well as males in biomedical studies. These mandates have enhanced generalizability and created unprecedented opportunities to discover sex differences. However, education in sound methods to consider sex as a subgroup category has lagged behind, resulting in a problematic literature in which study designs, analyses, and interpretations of results are often flawed. Here, we outline best practices for complying with sex-inclusive mandates, both for studies in which sex differences are a primary focus and for those in which they are not. Our recommendations are organized within the “4 Cs of Studying Sex to Strengthen Science: Consideration, Collection, Characterization and Communication,” a framework developed by the Office of Research on Women’s Health at the National Institutes of Health in the United States. Following these guidelines should help researchers include females and males in their studies while at the same time upholding high standards of rigor.