A new study from the Wellcome Trust Sanger Institute, published in Nature Communications, argues that too many animal experiments have failed to take into account sexual dimorphism—the traits that differ between sexes in a species, from size to bone density to coloring. This blind spot may be skewing the results of animal testing. And that could have big consequences for the conclusions that we take from animal studies and apply to humans.
Science has a long history of making incorrect assumptions about biological sex that skew testing on live subjects. For much of history, scientists have tended to regard female bodies as simply scaled-down versions of males, which meant that one could just test on men and draw conclusions about women’s medical needs. This has backfired repeatedly. In one notable case, in 2013, the US Food and Drug Administration had to cut the recommended dosage for zolpidem (Ambien) for women by half after it was discovered that taking a “normal” dose often resulted in serious overdoses for women.
The costs of neglecting female biomedical responses have been evident for a while now. Eight of the ten drugs withdrawn by the FDA between 1997 and 2001 (pdf) were taken off the market because of serious side effects for women, from birth defects in children to increased cancer risk. In most cases, the drugs were recalled after female patients went public with negative consequences. And evidence has shown that women’s bodies metabolize various medications in different ways, from antipsychotics to anesthetics—differences that have huge consequences for treatment and surgical practice.