Repetitive head hits are common in football, and they're also linked to debilitating brain injuries.
But rendering a definitive diagnosis typically means waiting for autopsy results after the player has died.
Now, a new study suggests that brain scans can reliably spot troubling signs of sports-inflicted neurological damage while a person is still alive.
The research also showed that more brain lesions show up on the scans the longer football players have engaged in the sport.
"A routine [MRI] scan might be able to capture long-term harm to the brain in people who have been exposed to repetitive hits to the head, like those from American football and other contact sports," concluded study author Michael Alosco.
Alosco is co-director of the Alzheimer's Disease Research Center Clinical Core with Boston University's School of Medicine.
He and his colleagues explained that what such MRIs are looking for are bright spots on the brain known as "white matter hyperintensities."
"They literally appear as bright white spots," said Alosco. "Anyone can see them. And they signal injury to the white matter of the brain."
Outside the context of contact sports, such spots typically are a sign of aging, he noted, "and it is common to see them in people who are older than 65."
Among the elderly, heart disease is often the root cause, Alosco said, because when the heart fails to deliver enough blood to the brain, the resulting oxygen deficit ends up injuring the person's small blood vessels and white matter.
"However, these hyperintensities can have many causes, and research also links them with progressive brain diseases like Alzheimer's disease," he added.
So, he and his team set out to see whether the same bright spots might be linked to repetitive hits to the head among athletes involved in contact sports.
In all, the study focused on 67 football players, along with eight others who were either soccer players, boxers or military veterans.
On average, the football players had 12 years of play under their belts (including 16 professionals and 11 semi-professionals).
By the time the study got underway, all the athletes had already died (at an average age of 67). And all had donated their brains for research into head injuries.
But all had also undergone brain scans while alive (at an average age of 62).
When Alosco and his colleagues reanalyzed those scans, they found that the longer a football player had played the sport, the more bright spots he had while alive.
In addition, for every additional "unit" of white matter spots, the risk for having serious small vessel disease and general white matter damage in the brain doubled.
Each additional unit of such markers was also linked to a tripling of the presence of a specific protein ("tau") that has long been linked to both Alzheimer's disease and a neurodegenerative disease called chronic traumatic encephalopathy (CTE).
In fact, autopsies confirmed that roughly seven in 10 of the athletes in the study had CTE, a precursor for dementia. And family members of the athletes in the study further confirmed that roughly two-thirds suffered from dementia.
The findings were published online Nov. 24 in the journal Neurology.
Alosco said the results are "exciting," given that they offer "a very practical way to study brain harm" in real time, rather than after the fact.
But a more sobering assessment was offered by Dr. Robert Glatter, an emergency medicine physician at Lenox Hill Hospital in New York City and a former sideline physician for the New York Jets. The study "adds to the argument to ban tackle football altogether," he said.
"The implications of the study are quite clear: repetitive head and body impacts over time -- whether concussive or subconcussive -- increase the risk for developing brain injury, indicating a long-term or cumulative effect," Glatter said.
And the problem is that, despite some effort to reduce risk, "playing contact football is inherently dangerous and unpredictable at best," raising the risk of CTE, cognitive impairment and neurodegenerative diseases like Alzheimer's and Parkinson's.
Still, another expert cautioned against overinterpreting the results until more research is completed.
The study only looked at athletes who had already developed brain injuries, noted Dr. Julie Schneider, associate director of the Alzheimer's Disease Center at Rush University Medical Center, in Chicago. And that, she said, makes it impossible to conclude that the bright spots in question actually predict such injuries.
What's now needed, said Schneider, are "studies starting with players prior to having symptoms." That will be the only way to "figure out the sequence of brain changes, and their relationship with dementia during life."
There's more on the link between football and brain injuries at NYU Grossman School of Medicine.
SOURCES: Michael Alosco, PhD, associate professor, neurology, and co-director, Alzheimer's Disease Research Center Clinical Core, and investigator, CTE Center, department of neurology, Boston University School of Medicine; Julie A. Schneider, MD, MS, professor of pathology and neurological sciences, and associate director, Rush Alzheimer's Disease Center, Rush University Medical Center, Chicago; Robert Glatter, MD, emergency medicine physician, Lenox Hill Hospital, New York City, and former sideline physician, New York Jets; Neurology, Nov. 24, 2021, online