Boston, Massachusetts, USA : Men who most frequently wore boxers had significantly higher sperm concentrations and total sperm counts when compared with men who did not usually wear boxers, according to new research led by Harvard T.H. Chan School of Public Health. The findings of this study, conducted in the Fertility Clinic at Massachusetts General Hospital, suggest that certain styles of men’s underwear may inhibit production of sperm.
“These results point to a relatively easy change that men can make when they and their partners are seeking to become pregnant,” said Lidia Mínguez-Alarcón, lead author of the study and research scientist at the Harvard Chan School.
The study will be published on August 8, 2018 in Human Reproduction.
While previous research has shown that elevated scrotal temperatures can adversely affect testicular function, studies on whether and how different styles of underwear may impact sperm production have been inconsistent.
For this study, the largest of its kind to look at underwear and semen quality, researchers collected information and semen samples from 656 men who were part of couples that were seeking treatment at a fertility center. The men, who were between the ages of 32 and 39, completed a survey that included questions about the style of underwear they wore in the previous three months. Options included boxers, jockeys, bikini, briefs, and other.
Among the study participants, 53% reported usually wearing boxers. Analysis of semen samples showed that these men had 25% higher sperm concentrations and 17% higher total sperm counts when compared with men who did not primarily wear boxers. Men who wore boxers also had higher percentages of motile sperm, or sperm that are capable of moving through the female reproductive system and fertilizing an egg. The most significant difference in sperm concentration was seen between men who wore boxers and men who wore jockeys and briefs.
In addition, analysis of blood samples collected from 304 of the study participants showed that men who wore boxers had 14% lower levels of follicle stimulating hormone (FSH) compared with men who didn’t wear boxers. FSH is known to play an important role in male fertility and is associated with sperm production. The simultaneous presence of lower sperm counts and higher FSH among men wearing tight-fitting underwear suggests the presence of a compensatory mechanism whereby the decreased sperm production among men in tighter underwear signals the brain to boost production of hormones that stimulate the activity of the gonads to try to increase sperm production.
“Beyond providing additional evidence that underwear choices may impact fertility, our study provides evidence, for the first time, that a seemingly random lifestyle choice could have profound impacts on hormone production in men at both the level of the testis and the brain,” said Jorge Chavarro, senior author of the study and associate professor of nutrition and epidemiology.
Other Harvard Chan School study authors included Audrey J. Gaskins, Yu-Han Chiu, Carmen Messerlian, Paige L. Williams, Jennifer B. Ford, and Russ Hauser.
Funding for this study came from National Institutes of Environmental Health Sciences grants R01ES022955, R01ES009718, P30ES000002, and K99ES026648.
“Type of underwear worn and markers of testicular function among men attending a fertility center,” Lidia Mínguez-Alarcón, Audrey J. Gaskins, Yu-Han Chiu, Carmen Messerlian, Paige L. Williams, Jennifer B. Ford, Irene Souter, Russ Hauser, Jorge E. Chavarro, Human Reproduction, online August 8, 2018, DOI: 10.1093/humrep/dey259
“The study provides reasonably strong supporting evidence that wearing tighter underwear might cause mild, but significant, impaired sperm production in men,” noted Richard Sharpe, an honorary professor from the University of Edinburgh’s MRC Centre for Reproductive Health who was not involved in the research.
Ashely Grossman, professor of endocrinology at Oxford Centre for Diabetes, Endocrinology and Metabolism, agreed, saying the results were robust enough to merit a small lifestyle change when in doubt.
“It is a simple measure to wear boxer shorts when there is uncertainty regarding fertility,” he commented.
At the same time, none of men surveyed – whether they wore boxers, jockeys or bikini briefs – showed sperm counts below the normal range.
Experts noted a number of gaps in the new study that left room for uncertainty and highlighted the need for follow up research.
While each participant provided a sperm and blood sample, sartorial habits were self-reported.
The study was also not a clinical trial – the gold standard in health research – but a search for statistically significant correlations, which can only point to possible causes.
Also, the study did not measure actual pregnancy outcomes, so it was unclear whether the differences in sperm count and quality uncovered actually made a bottom-line difference in the desired outcome.
Harvard T.H. Chan School of Public Health brings together dedicated experts from many disciplines to educate new generations of global health leaders and produce powerful ideas that improve the lives and health of people everywhere. As a community of leading scientists, educators, and students, we work together to take innovative ideas from the laboratory to people’s lives—not only making scientific breakthroughs, but also working to change individual behaviors, public policies, and health care practices. Each year, more than 400 faculty members at Harvard Chan School teach 1,000-plus full-time students from around the world and train thousands more through online and executive education courses. Founded in 1913 as the Harvard-MIT School of Health Officers, the School is recognized as America’s oldest professional training program in public health.