Boxers or briefs? Men who choose boxers have higher sperm counts than those who favor briefs, according to the largest study ever to look at a long-suspected link between tight underwear and lower sperm production.

The study of 656 men, published Wednesday in the journal Human Reproduction, adds to evidence that underwear choices really do matter. The likely reason: tight undies slightly raise testicle temperatures and that’s bad for sperm.

The difference might be enough to affect fertility in some men who start out with borderline sperm numbers, said the study’s lead author, Jorge Chavarro, an associate professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health.

Those men “might benefit quite a bit from changing the type of underwear they wear,” he said.

The study involved men ages 18 to 56 visiting a fertility clinic at Massachusetts General Hospital in Boston. Researchers collected semen and blood samples and asked the men what kind of underwear they usually wore. Just over half said they mostly wore boxers; the rest wore briefs, bikinis or other tight styles.

read more at usatoday.com