As middle-aged champion boxer Bernard Hopkins, 46, prepares to fight 29-year-old Chad Dawson this Saturday, he boasts that he feels as good as he did a decade ago.

On the undercard, 52-year-old Dewey Bozella makes his professional boxing debut against Larry Hopkins, an opponent also 2 decades younger.

While athleticism at their ages is impressive, both match ups raise the same question — at what age do the health risks of boxing become too great?

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For long-time fighters like Hopkins, the effects of boxing have been well-studied. As many as 40 percent of ex-boxers have symptoms of chronic brain injury. One study found that over 80 percent of professional boxers had major scarring on brain MRI scans. It can be assumed that continuing to withstand head trauma worsens this outlook.

Most of the data collected, though, is on professional boxers who were involved in more than twelve bouts who fought for decades, like Hopkins. There is currently no research on boxers who start later in life.

“However, anytime you’re talking about people taking repetitive risks to the head, the brain doesn’t like that,” says Dr. Jeffrey Kutcher, director of Michigan NeuroSport at the University of Michigan, who researches the effects of sport injuries on the brain.

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Recently publicized concerns about boxing have focused on youth and brain development, which is, arguably, not a concern for new, older boxers like Bozella. By a person’s 20’s, the maturing processes of the brain are complete.

But, Dr. Gail Rosseau says that doesn’t mean they are out of the water.

“We’re always at risk. Every blow to the brain is a new insult to the brain,” says Rosseau, a neurosurgeon at North Shore University Health System in Illinois.Brain injury can range from a minor concussion, where the person feels foggy for a few minutes, to debilitating injuries like bleeding in the brain.

Middle-aged boxers are no more likely to sustain a concussion than a younger opponent. But, they are, in fact, at higher risk for brain bleeds, such as subdural hematomas, and worse outcomes.

“The older you are when you sustain a traumatic brain injury [as in boxing], the less likely you are to recover to your pre-injury status,” says Dr. Rosseau. “The typical time course for recovery from the same blow is longer in the older age group.”

Bozella’s efforts, however, are not completely dismal.

WATCH NBC PHILADELPHIA’S VIDEO FEATURE ON BOZELLA HERE:
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Despite the risks of head injury, middle-aged men engaging in high-impact aerobic activity does have clear benefits on brain health.

“Aerobic activity and cardiovascular fitness helps your brain at every age, but particularly as you get older,” says Rosseau. “But, you don’t have to have someone slam a fist into your face.”

Ironically, aerobic exercise later in life — which, in this case, includes boxing — helps prevent the development of Alzheimer’s disease.

Dr. Kutcher doesn’t think Bozella’s decision to start fighting at his age is outrageous. He points out that the risks are real, but rare.

“If it were my father who wanted to box at age 50, I think it’s a reasonable thing to do,” Kutcher says.

Whether talking about boxers who have fought for decades without obvious problems or new boxers, much is unknown about their future. The effects of an impact on the brain are unpredictable. And, its consequences are often delayed.

“If you take a strong blow and you shake it off, and keep going — did that do anything to you or not?” asks Rosseau. “Are they really fine? We don’t know.”