NFL Concussions Linked to Low Testosterone, Erectile Dysfunction

Damian McNamara

August 28, 2019

Self-reported concussion symptoms in former US professional football players are linked to a greater likelihood of low testosterone levels and erectile dysfunction (ED), new research suggests.

A large, retrospective study showed that approximately 1 in 5 former National Football League (NFL) players who experienced concussive symptoms reported low testosterone levels, or 18% of 3409 individuals assessed. Another 23% of the participants reported ED.

For the first time, findings also showed a dose-response relationship linking a history of more concussive symptoms with a greater risk for these long-term outcomes.

"Clinicians treating patients with head trauma, including but not only football players, should inquire proactively about symptoms of ED and low testosterone," senior author Andrea L. Roberts, PhD, research scientist in the Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, Massachusetts, told Medscape Medical News.

"Our findings also suggest that it may be important for clinicians to assess patients with concussion history for the presence of neurohormonal changes," Roberts added. "Prompt evaluation of ED is critical because it can signal the presence of other conditions, including heart disease and diabetes."

The study was published online August 26 in JAMA.

Dearth of Large Studies

"Very few prior studies have linked concussion with ED or low T," Roberts said. In addition, existing studies are relatively small, evaluate boxers or soldiers, and focus on patients admitted to clinics, she added.

One notable exception is a study that compared ED rates after traumatic brain injury (TBI) in 73,000 clinical patients and 21,800 control persons. Greater TBI severity was associated with higher risk for ED over 10 years.

"However, this study focused only on medically evaluated single head injuries, rendering results less applicable to often underdiagnosed sports-related head traumas," the current investigators write.

To learn more, they contacted participants in the Football Players' Health Study, which recruited men who played for the NFL after 1960. The researchers analyzed responses to questionnaires from 3506 of these former players received as of March 2017.

The mean age of the participants was 53 years, and the mean number of football seasons played was almost seven.

The investigators quantified self-reported concussion symptoms, including headaches, nausea, dizziness, and loss of consciousness, into none, 2 to 5 times, 6 to 10 times, or 11 or more times for each symptom. Participants were classified as having a history of low testosterone and/or ED if they answered yes to the question, "Has a medical provider ever recommended or prescribed medicine for: (1) low testosterone or (2) ED?"

Significant Link

A total of 611 former players (18%) reported indicators of low testosterone. Another 755 respondents (23%) reported indicators of ED. An additional 335 (10%) experienced both low testosterone and ED.

The investigators also assessed current medication use and found that 40% of the former players in the low testosterone group were currently taking medication, as were 50% of those in the ED group.

Interestingly, a dose-response relationship emerged in which the greater number of reported concussion symptoms aligned with greater indicators of low testosterone and ED.

After adjusting for age and race, the researchers linked a greater number of symptoms to a statistically significant increased likelihood for low testosterone (odds ratio [OR], 3.49; 95% confidence level [CI], 2.68 – 4.56). They found a similar association with ED (OR, 2.41; 95% CI, 1.87 – 3.11).

"Even men at the lower end of concussion exposure had increased risk of these outcomes, but risk grew with each increase in concussions," Roberts said.

With regard to comorbidities, models that adjusted for race and age indicators showed that low testosterone levels and ED were significantly associated with hypertension, high cholesterol levels, diabetes, heart conditions, prescription pain medication, reproductive cancer, sleep apnea, obesity, and mood disorders.

The Bigger Picture

"To our knowledge, this is the first large study to examine low testosterone levels and ED, albeit indirectly, in a nonclinical population with a high prevalence of repeated injuries," the investigators write.

The research adds to what is known about the long-term effects of NFL-related concussions, they note.

"Most studies have short follow-ups of only 1 year or less after the concussion. So, we don't know whether these conditions persist or whether they resolve," Roberts said.

In the current research, concussion remained linked with ED and low testosterone in men who had last played more than 20 years ago. "These findings suggest this is a very long-term issue," she added.

In addition, "risk of ED increases with age, raising the question of whether concussions are only associated with ED as men age. But we found the same risk in men younger than 50 as in older men, suggesting that young men may experience ED and low T subsequent to concussions," Roberts said.

"Replication of our findings among nonprofessional football players and in the general population is a critical next step," the researchers write.

"It's very important to better understand the relation between concussion and ED and low T among high school and college football players, since many more people play the sport at those levels, and in the general population as well," Roberts said.

"In addition, we need to study potential hormonal and sexual effects of concussion on girls and women," she noted.

Reminder for Clinicians

Asked to comment by Medscape Medical News, Randolph W. Evans, MD, clinical professor of neurology at Baylor College of Medicine, Houston, Texas, who is a member of the advisory board for Medscape Neurology, said the findings are consistent with prior studies "showing pituitary dysfunction due to sports related concussion."

He cited as an example a June 2019 study that linked pituitary dysfunction to sports-related TBI.

"I concur with the authors that it is important to query susceptible patients and do pituitary testing in symptomatic individuals," said Evans, who was not involved with the current research.

The study is "very interesting," Razib Khaund, MD, director of sports medicine at Care New England Health Systems and clinical assistant professor of medicine at the Alpert Medical School at Brown University, Providence, Rhode Island, told Medscape Medical News when also asked to comment.

"The article highlights the importance of concussion and in particular repetitive concussions on general health," he said.

"The premise of the article is very interesting and not unreasonable. It serves as a reminder for clinicians who care for patients with history of concussion to be wary of possible far-reaching implications on general health," Khaund added.

The study was funded by the Sidney R. Baer Jr Foundation, the National Science Foundation, DARPA, the Football Players Health Study at Harvard University, Harvard Catalyst/the Harvard Clinical and Translational Science Center, the NFL Players Association (NFLPA), and grants from the National Institutes of Health. Roberts reported receiving grants from the NFLPA during the conduct of the study. Evans was an examiner as part of the NFL concussion settlement from May 2017 to June 2018 and evaluated 395 retired NFL players. Khaund has reported no relevant financial relationships.

JAMA Neurol. Published online August 26, 2019. Full article

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