More than 3,400 former National Football League (NFL) players were asked about their history of concussion symptoms by a team of researchers at Harvard University, and whether they were taking or had been recommended medication for low testosterone or erectile dysfunction (ED).
After controlling for other variables including hypertension, diabetes, high cholesterol and so more, they found that former players in the "very high" concussion symptom group were about twice as likely to report low testosterone and ED compared to the group with the fewest concussion symptoms.
"We've found a really strong relationship between reports of concussion symptoms, and the likelihood that the guys reported erectile dysfunction, low testosterone," Rachel Grashow, lead author of the paper that appeared in JAMA Neurology told AFP.
Among all the ex-players, whose mean age was 53, indicators of low testosterone and ED were about 18 percent and 23 percent respectively.
The authors wrote in the paper that a possible explanation was concussion associated hypopituitarism, a disorder of the pituitary gland found at the base of the brain which regulates hormone production.
Limitations included that the researchers did not directly measure low testosterone or ED but instead relied on self-reported indicators that were then used as proxies.
The researchers also initially tried to contact more than 13,000 ex-players but only got responses from 25 percent.
Grashow admitted that "probably a lot of healthy guys don't sign up because they don't think need to" but she believed the most impaired players were also missing, leaving a relatively good set of data.
Grashow said the study built upon prior work in smaller studies exploring hormonal dysfunction in boxers and military personnel who had sustained head injuries.
Nevertheless, she added the team considered the work to be "more of a gateway study, with the hope of following up with this population and others to dig into how severity of ED plays a role in this story."