A study published on the Oxford University Press’ academic website found that men who wore boxers had a higher sperm count than men who wore briefs. The study included 656 male partners from couples seeking treatment for infertility. The men self-reported whether they wore boxers or briefs more frequently in the previous three months. Semen samples were collected and analyzed to look for differences in sperm concentration, sperm count, motility and sperm morphology.
Men who reported wearing boxers more frequently had a higher sperm concentration, higher sperm count and higher motile count, according to the study.
“High scrotal temperatures have been associated with the alteration of [the] production of sperm,” Lidia Mínguez-Alarcón, a research scientist in the department of environmental health at Harvard University and the lead author of the study, told HuffPost.
According to the Mayo Clinic, high temperatures can weaken the production of sperm and affect how well they function. Mínguez-Alarcón said that wearing tight clothing puts the testicles closer to the rest of the body, keeping them warmer and resulting in fewer sperm. “That is the reason why the testicles are outside the body, because they are between 2 and 3 degrees Celsius cooler,” she said.
Although the study looked at several factors possibly affecting the men’s fertility, it had some limitations. For starters, it didn’t find a causal link between the type of underwear a man wears and fertility; it showed only a correlation.
Additionally, all the men in the study were a part of couples having fertility issues, so it’s possible that the women had problems with fertility. The study looked only at straight couples, and according to Mínguez-Alarcón, trans men were not included in the research.
Finally, since the men self-reported the type of underwear they most frequently wore, it’s possible that there was “measurement error and misclassification of the type of underwear worn,” the researchers wrote.
The study nods to an often underdiscussed topic when it comes to fertility: men. An estimated 15 percent of couples face infertility issues, according to the Mayo Clinic, and male infertility plays a role in up to half those cases. But the burden of not being able to have children “falls disproportionately on women,” according to the World Health Organization Advisory Committee on Health Research.
Many infertility treatments are geared toward women, such as in vitro fertilization and drugs that stimulate ovulation and increase egg production. According to the University of Cambridge, research has shown that male fertility is “culturally invisible” and isn’t as openly talked about, even though it is just as common as infertility in women.
While heat may just be one factor in male fertility issues, a variety of others could also affect sperm production. Hormone imbalances, age, stress and lifestyle factors such as diet and drug use can also result in male infertility.