Boxers or briefs: Study finally settles whether a man’s underwear really affects his fertility

A large study of 27,000 men found that wearing tight underwear was associated with poorer semen quality and more reports of erectile dysfunction and premature ejaculation. The findings add weight to the idea that underwear choice may relate to reproductive and sexual health, though they do not prove that tight underwear causes these problems.

Researchers compared men wearing tighter and looser underwear, accounting for factors including smoking, alcohol use and existing conditions. The tight-underwear group had 108% higher odds of sperm with DNA damage. Earlier studies have produced mixed results: a 2018 study linked boxer shorts to higher sperm counts among men seeking fertility treatment, while a Thai study found no clear difference in sperm count.