Tight clothes can also put pressure on the bladder and encourage the breeding of dangerous bacteria by the groin, which can then enter the body and cause urinary tract infections. Tight fitting clothes are also linked to low sperm count and fungal infections
Too much heat can lower sperm count (but not enough to act as a form of birth control). So tight clothing and underwear that keep testicles closer to body heat might, in theory, affect sperm count
