Lab rats are overwhelmingly male, and that's a problem

Concern is growing that ignoring or downplaying differences in sex as a biological variable -- whether in cells under a microscope or in lab animals -- is undermining biomedical research at the earliest stages. This matters because many diseases -- including Covid-19 -- affect men and women differently.

Five years ago, University of Maryland researcher Alisa Morss Clyne was studying pulmonary hypertension -- a type of high blood pressure that affects the arteries in the lungs -- in human cells she had cultured in her lab. But the results she was seeing just didn't stack up. "We had these huge error bars. It didn't make any sense," she said. "And we said, OK, let's just graph it by male versus female, and what we found was really interesting."