Men Who Wear Tight Underwear Have Higher Rates of Erectile Dysfunction and Poorer Sperm Quality, Study Finds
Men who routinely wear tight underwear have poorer sperm quality and higher rates of erectile dysfunction and premature ejaculation than men in loose boxers, according to the largest study of its kind involving 26,836 men in China.
The research, which links tight underwear to key markers of fertility and sexual health, suggests that something as mundane as underwear choice could be tied to semen quality and sexual function.
Published in the Asian Journal of Andrology, the study is described by its authors as the biggest investigation to date into how tight underwear may affect sperm and sexual performance. All participants were attending a fertility clinic at The First Affiliated Hospital of the University of Science and Technology of China in Hefei, with a median age of 30.
Over the previous three months, 21,221 men reported wearing loose boxer shorts most often, while 5,615 said they mainly wore tight styles such as Y-fronts, thongs and boxer briefs.
Sperm Quality Divide in Tight Underwear Study
Researchers adjusted their analysis for health and lifestyle factors including smoking, alcohol use, varicocele and prostatitis, which were more common in the tight underwear group. Even after that adjustment, tight underwear remained associated with poorer semen quality.
Men who wore tight underwear had 18 per cent higher odds of producing less semen and 12 per cent higher odds of having fewer motile sperm. They also had 48 per cent higher odds of having fewer normally shaped sperm and 108 per cent higher odds of having more sperm with damaged or fragmented DNA.
The authors, led by urologist Xue-Chun Hu, wrote that the findings were 'consistent with the hypothesis that scrotal heat stress contributes to impaired spermatogenesis'. Tight briefs reduce airflow and have been shown to raise scrotal temperature by up to 1°C compared with boxers, and sperm develop best at around 2°C to 3°C below core body temperature.
Tight Underwear and Sexual Function Problems
In an exploratory analysis using two standard questionnaires, the International Index of Erectile Function-5 and the Premature Ejaculation Diagnostic Tool, erectile dysfunction was reported by 62.7 per cent of men in tight underwear, compared with 57.8 per cent of those in loose underwear.
Premature ejaculation affected 30.8 per cent of the tight underwear group and 23.2 per cent of men in boxers. Tight underwear remained associated with higher odds of both conditions after statistical adjustment.
The researchers suggested that prolonged wear might also lower testosterone secretion and contribute to sexual dysfunction, though this possible mechanism remains unproven.
How Strong Is the Evidence?
The study cannot show that tight underwear causes fertility problems or erectile dysfunction, only that they are associated. Most participants were already seeking fertility assessment, which the authors say may introduce selection bias and limit how far the findings apply to the wider population.
Earlier research has mainly involved small groups, often men with existing fertility issues. One study of 3,041 couples in the US and Canada found little evidence that heat around the scrotum from saunas, laptops, seat heaters or tight underwear changed the chances of conception.
Other reviews have reported global declines in sperm counts, with some researchers pointing to pollutant exposure as a possible major factor rather than underwear choice.
It is not known whether switching to looser underwear improves the chances of conceiving. Health agencies and clinicians advise men with concerns about fertility or sexual function to seek medical advice.