Former Buffalo Bills fullback Cookie Gilchrist died in 2011 with cognitive impairment and Stage 4 Chronic Traumatic Encephalopathy, diseases that research links to mild head traumas common among football players.

The New York Times presents images of the brain of Gilchrist, who died in 2011 at the age of 75. The browned part shows the disease around the amygdala and temporal cortex. A normal brain would be mainly off-white in color.

The Times piece references an article recently published in Brain: A Journal of Neurology. Researchers looked at brains from 85 former athletes, military veterans and civilians with a history of repetitive mild traumatic brain injury.

Of the professional athletes, the vast majority showed evidence of irreversible brain diseases. Still, the research doesn’t necessarily predict which types of athletes would develop such injuries and subsequent diseases.

“It’s a gambler’s game to try to predict what percentage of the population has this,” Chris Nowinski, a co-author of the study and a co-director of the Center for the Study of Traumatic Encephalopathy at Boston University School of Medicine, told the New York Times. “Many of the families donated the brains of their loved ones because they were symptomatic. Still, this is probably more widespread than we think.”

Aside from Gilchrist, other local athletes have shown evidence of long-term brain damage due to sports. Former Buffalo Sabres player Rick Martin, who died in 2011, was diagnosed with chronic traumatic encephalopathy. He showed no outward symptoms of of CTE, which sometimes manifests itself much like Alzheimer’s, Parkinson’s and Lou Gehrig’s disease might, ABC News reported.

“Rick Martin’s case shows us that even hockey players who don’t engage in fighting are at risk for CTE, likely because of the repetitive brain trauma players receive throughout their career,” Nowinski said in the 2011 ABC interview.

Though the study only looked at brains of athletes who engaged in sports as adults, brain trauma among child athletes is increasingly discussed in news media.

According to a UB study, reports of concussions in sports have more than quadrupled in the last decade.