Why Guinea Pigs Are Mostly Men

An employee takes a sample at the lab of a Polar brewery in Maracaibo, Venezuela (Isaac Urrutia / Reuters)

Last week, I wrote about the lives of professional guinea pigs, people who support themselves mostly or entirely with money earned from professional drug trials. All of the guinea pigs I talked to for the story were men—not something I’m particularly happy about, but unfortunately, it’s not too far off from the makeup of the research-subject population. Overwhelmingly, clinical-trial research is still mostly research done on men.

A piece of history that didn’t make it into my piece, but that I found fascinating (and frustrating): A major reason women are so underrepresented in clinical trials today is because of thalidomide, the drug that caused thousands of birth defects in the 1950s and ‘60s.

In 1977, spooked by the thalidomide disaster, the FDA drew up guidelines encouraging researchers to ban women of childbearing age from their studies. That’s no longer the case—the FDA, after receiving blowback from women’s-health groups, reversed its position in 1993, the same year Congress passed a law requiring all NIH-funded studies to include both sexes. But it’s hard to argue that the decades-long ban hasn’t affected how women are included today.

I wrote about this issue in a different context last September, looking at the imbalance in the research that happens before human bodies get involved: studies done on cells, for example, or rats. In those cases, subjects still tend to skew pretty heavily male.

Granted, as I noted back then, women (and female cells, and female rats) can also make for trickier research subjects. There are monthly hormone fluctuations to account for, and most early-stage trials require subjects who aren’t taking any prescriptions, which can rule out women on birth control.

The problem is, leaving them out just makes for surprises further down the line. Ideal dosage can be different for men than it is for women. Same with side effects. Often, these things are sussed out long after a drug’s already made it to market—meaning, in other words, that the research subjects paid by the lab aren’t the only guinea pigs.