Miami Dolphins quarterback Tua Tagovailoa said he briefly considered retiring from football over the concussions he suffered last season.

He decided to return, in part, because of feedback he received from doctors, although he wouldn't name them. He'll make his season debut Sunday against the Los Angeles Chargers, nine months since a series of concussions ended his 2022 season.

In an April news conference, Tagovailoa said he was told that the series of concussions he suffered in 2022 would not make it any more likely that he would get another one in 2023, and that chronic traumatic encephalopathy − the neurodegenerative disease more commonly known as CTE − "wasn't going to be a problem" for him.

"It’s only when you’re constantly hitting your head against something," Tagovailoa continued. "So I think that tailors more towards linebackers, O-linemen, D-linemen − guys that are constantly going at it."

Tagovailoa's comments quickly raised eyebrows among neurologists and academics who study CTE. And they belie the complexity and uncertainty of the health risks he is assuming as he returns to the NFL this fall.

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"If somebody told him he doesn’t have to worry about CTE, then he is definitely being misled, based on what we know today," said Chris Nowinski, the co-founder and chief executive officer of the nonprofit Concussion Legacy Foundation.

USA TODAY Sports spoke with Nowinski and other experts in concussion care and CTE research to better understand what Tagovailoa's 2022 head injuries mean for him in 2023 and beyond. Is he more likely now to suffer another concussion? Is he at a greater risk of getting CTE? Does the position he plays change the risk analysis at all?

The answers to those questions are complicated, experts said − and not always clear. And Tagovailoa, for his part, isn't dwelling on them, saying his mental and physical preparation are improved since his last game, in December.

"I think I’m far, far ahead," he said Thursday. "It hasn’t been a thought ever since it’s happened. Ever since I’ve been cleared, it’s never been a thought to look back at that."

How many concussions did Tua Tagovailoa have?

Tagovailoa will make his season debut nearly one year after he suffered a suspected concussion in a Week 3 game against the Buffalo Bills, wobbling and struggling to stay on his feet after taking a hit. The team initially announced that he had a head injury before later claiming he had hurt his back.

Just four days later, Tagovailoa displayed a fencing response − a sign of serious brain injury − after another hit and was stretchered off the field during a primetime game against the Cincinnati Bengals, prompting a joint investigation by the NFL and NFL Players Association into whether their concussion protocols had been adequately followed in the Bills game. Tagovailoa returned one month later and started each of Miami's next nine games, but then another concussion on Christmas Day brought his season to a premature end.

Tagovailoa said in April that, while he considered walking away from the NFL this winter, he decided against it.

"I always dreamed of playing as long as I could to where my son knew exactly what he was watching his dad do," he told reporters. "Yeah, it’s my health, it’s my body. I feel like this is what’s best for me and my family. I love the game of football. If I didn’t, I would’ve quit a long time (ago).”

It's unclear how many other concussions Tagovailoa has had during his football career, though he has publicly acknowledged at least one − in December 2019, during his final season at Alabama.

Is Tua Tagovailoa now more likely to get another concussion?

Tagovailoa and Dolphins general manager Chris Grier have each been firm when asked this question. They've said the answer is no.

"From what our doctors (said) and the consultants we’ve talked to through the NFLPA, that is not a true statement," Grier said in a January news conference. "I don’t think he’s any more prone (to getting concussed) than anyone else."

Experts, however, are less certain. While individuals heal from concussions differently, research suggests one of the greatest risk factors for sustaining a concussion is having previously had one.

"There’s something about that previous concussion that can make the brain more vulnerable − especially multiple concussions," said Julie Stamm, a clinical assistant professor in the Department of Kinesiology at the University of Wisconsin-Madison.

"The data would suggest that there is an increased risk of concussion, because he had these previous concussions. How much increase? We can’t really say. Maybe it’s not actually that much."

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Teena Shetty is an associate professor of clinical neurology at Weill Cornell Medical College and a neurologist at Hospital for Special Surgery in New York. In conversations about the potential risks of returning to play, she said it's important to keep in mind that not all concussions are made equal − and that the severity of each head injury matters, in addition to the cumulative number of them.

"Concussions are more qualitative than quantitative," said Shetty, who is not involved in Tagovailoa's treatment. "There’s so many factors. ... How bad was the blow? What symptoms did you have afterwards? How many symptoms did you have? When did your symptoms resolve? All of these things contribute to the medical return to play decision-making."

Is Tua Tagovailoa still at risk for CTE?

Nowinski said he was frustrated to hear that Tagovailoa was told CTE "wasn't going to be a problem" for him. Research indicates the quarterback is likely still at risk of getting the neurodegenerative disease − and there is a chance he, like other NFL players, might already have it.

That heightened risk, however, stems from the number of years he has spent playing tackle football rather than the number of concussions with which he's been diagnosed. Nowinski noted that more than 91% of former NFL players whose brains have been studied by Boston University's CTE Center were found to have CTE. And recent research suggests that athletes who play more than 11 years of football, or pick up the sport at a young age, have a greater risk of later having the disease. (Tagovailoa, 25, has been playing football since he was at least 8 years old.)

"To me, the CTE comments just came down to informed consent," Nowinski said. "Doctors should not be telling NFL players that they’re not at risk."

Because CTE can only be diagnosed posthumously, it is impossible to draw conclusions about when the disease sets in. But a study published late last month examined the brains of 152 athletes who played contact sports and died before the age of 30, and found that 63 of them (41.4%) had CTE at the time of their deaths. Most of the athletes (48 of the 63) diagnosed with CTE had played football as their primary sport, according to the study.

Is Tua Tagovailoa safer because he plays quarterback?

Tagovailoa indicated in April that he believes this is the case, and research published earlier this year supports the idea. A June study found that offensive and defensive linemen participate in less jarring but more frequent hits, subjecting them to higher levels of force over the course of the season and putting them at the highest risk of brain injury. Quarterbacks and wide receivers are on the opposite end of the spectrum.

Nowinski, however, said there are no clear positional differences in the rates at which CTE has been found in former NFL players, per the CTE Center's brain bank. He described the study's conclusion that quarterbacks are at less risk as "almost aspirational," at least for now.

The fear is that, while quarterbacks might be subjected to less frequent hits, they also take some of the hardest ones − a blindsided blow from a 300-pound defensive lineman, for example.

"Even though (quarterbacks) will be sustaining fewer impacts, and that’s a good thing, sometimes they sustain bigger impacts − and that’s still concerning," Stamm added.

"While the risk might be less, it’s not zero. So I think that’s an important thing to understand."

Stamm also cautioned that the long-term health risks of concussions and other brain injuries go far beyond CTE.

"CTE gets so much attention when it comes to long-term risks, but there’s growing evidence that there (are) psychological or psychiatric conditions that have been associated with concussions," she said, citing research that individuals who suffered three or more concussions were found to have an increased risk of depression or cognitive impairment later in life.

Tagovailoa, for his part, has said he's tried to limit future head injuries by strengthening muscles in his neck and taking up jiu-jitsu, in hopes that it will help him learn how to fall more gracefully. Nowinski and Stamm said there's reason to believe those efforts might help − though they can't entirely eliminate the chances that Tagovailoa will suffer another concussion.

"It just comes down to: How much risk are you willing to take?" Nowinski said. "When we’re young, we’re willing to take a lot − though we may not think it was a good idea when we’re in our 40s."

Contributing: Safid Deen

Contact Tom Schad at tschad@usatoday.com or on social media @Tom_Schad.

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