With infertility affecting 8%-12% of couples worldwide, and 40%-50% of these cases being found to be a problem with males, the “boxer or brief” debate is not as whimsical and irrelevant as some think. There is a popular belief that the type of underwear men wear has an effect on their fertility. To answer the question as comprehensively as possible, a recent study was conducted that involved taking semen and blood samples from 656 men being treated for infertility. Of the more than 50% of men who said they regularly wore boxer shorts, 25% had a higher sperm concentration, a 17% higher total sperm count, and 33% more swimming sperm than men who regularly wore briefs, bikinis, and jockey shorts.
P.S. According to the study mentioned above, men who reported frequently wearing boxer shorts had 14% lower serum level of follicle-stimulating hormone (FSH), which signals the hypothalamus to produce more gonadotropin to increase FSH production.