Former NFL players who have experienced head injuries — namely concussions — may be more likely to also experience low testosterone and erectile dysfunction (ED), a new Harvard study found.

The study, published in the JAMA Neurology Monday, was based on a survey of more than 3,400 NFL players — which researchers with the Harvard T.H. Chan School of Public Health and Harvard Medical School noted represents “the largest study cohort of former professional football players to date.”

The survey was conducted between 2015 and 2017, according to a news release regarding the findings.

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For the survey, “participants were asked to report how often blows to the head or neck caused them to feel dizzy, nauseated or disoriented, or to experience headaches, loss of consciousness or vision disturbances— all markers of concussion. Responders were grouped in four categories by number of concussive symptoms,” researchers explained.

“Next, the former players were asked whether a clinician had recommended medication for either low testosterone or ED, and whether they were currently taking such medications.”

By the end, researchers found those who reported the most concussion symptoms were two-and-a-half times more likely to say they were either recommended to take, or are currently taking, medication for low testosterone compared to those who reported the fewest symptoms. Similarly, those who reported the most concussion symptoms were roughly two times more likely to say the same about ED medication.

“Notably, even former players with relatively few concussion symptoms had an elevated risk for low testosterone, a finding that suggests there may be no safe threshold for head trauma,” the researchers added.

“Former players with ED may be relieved to know that concussions sustained during their NFL careers may be contributing to a condition that is both common and treatable." — Rachel Grashow, the study's lead author

Overall, 18 percent of participants reported low testosterone, while 23 percent reported ED. About 10 percent said they experienced both.

Though the findings are observational and do not prove a definitive link between head trauma and ED, the results “do reveal an intriguing and powerful link between history of concussions and hormonal and sexual dysfunction, regardless of player age,” the researchers said.

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“Notably, the ED risk persisted even when researchers accounted for other possible causes such as diabetes, heart disease or sleep apnea, for example. Taken together, these findings warrant further study to tease out the precise mechanism behind it,” they noted.

Injury to the pituitary gland — a small organ at the base of the brain that’s responsible for hormone production — could affect testosterone levels and ED, researchers said of a possible explanation.

“Former players with ED may be relieved to know that concussions sustained during their NFL careers may be contributing to a condition that is both common and treatable,” Rachel Grashow, a researcher at the Harvard T.H. Chan School of Public Health and the study’s lead author, said in a statement.