Too tight? Huge Chinese study finds link between tight underwear and reduced sperm quality

A large Chinese study of 26,836 men found a link between wearing tight underwear and reduced sperm quality, including lower volume, fewer normal sperm cells, and increased genetic damage. Researchers suggest that elevated scrotal temperature may be the cause, but emphasize that no direct causal relationship has been proven.

A comprehensive Chinese study involving 26,836 men who sought fertility evaluation at the hospital affiliated with the University of Science and Technology of China found a link between wearing tight underwear and reduced sperm quality. The study, published in the Asian Journal of Andrology, compared 21,221 men who wore loose underwear (boxers) with 5,615 men who wore tight underwear (briefs or thongs) in the three months prior to testing. Among tight-underwear wearers, there was a decrease in semen volume, fewer sperm cells with normal motility, and a 48% lower rate of cells with normal morphology. There was also a twofold increase in the prevalence of genetic damage in sperm cells – 10.7% versus 5.8%. The researchers hypothesize that tight clothing raises scrotal temperature by half a degree to a full degree Celsius, which may impair the final maturation stages of sperm cells. However, the researchers emphasize that the study is observational only and no direct causal link has been proven, and since the study was based on men who had already sought fertility testing, it is uncertain whether the findings can be generalized to the entire population.