As you watch the Super Bowl on Sunday, consider the price that athletes may be paying for those head-slamming tackles: two new studies highlight the long-term dangers of sport-related concussion. Results released by Boston University show that former Tampa Bay Buccaneer Tom McHale, who died last year from a drug overdose at the age of 45, suffered from chronic traumatic encephalopathy (CTE), a degenerative brain disease caused by head trauma. McHale is the sixth former NFL player since 2002 to be diagnosed postmortem with CTE; two of the six committed suicide. The researchers also discovered early evidence of CTE in a recently deceased 18-year-old boy who suffered multiple concussions playing high-school football–the youngest case to date.

According to the Los Angeles Times,

The damages in both cases were similar to those observed in boxers who have taken severe beatings to the head, said [Dr. Ann C. McKee of Boston University’s Center for the Study of Traumatic Encephalopathy, who performed the biopsy]. Although they are also similar to the changes seen in Alzheimer’s disease, she added, “they represent a distinct disease with a distinct cause, namely repetitive head trauma.”

Boston University and the Sports Legacy Institute (SLI), a nonprofit dedicated to studying the effects of concussions and other sports-related brain injuries, have spearheaded a program to convince additional professional athletes to donate their brains after death.

According to a press release from Boston University,

CTE, a progressive neurodegenerative disease caused by repetitive trauma to the brain, is characterized by the build-up of a toxic protein called tau in the form of neurofibrillary tangles (NFTs) and neuropil threads (NTs) throughout the brain. The abnormal protein initially impairs the normal functioning of the brain and eventually kills brain cells. Early on, CTE sufferers may display clinical symptoms such as memory impairment, emotional instability, erratic behavior, depression and problems with impulse control. However, CTE eventually progresses to full-blown dementia. McHale died due to a drug overdose after a multi-year battle with addiction. Expert consensus is that drug abuse of any kind would never cause the neuropathological findings of CTE seen in McHale.

Due to the growing strength of these findings linking brain trauma on the football field to CTE, a number of living former NFL players have recently agreed to join three-time Super Bowl champion Ted Johnson and seven other former NFL players to donate their brains to Boston University School of Medicine upon death.

A second study looked at the long-term impact of more subtle injuries, finding that healthy former athletes still showed mild signs of cognitive impairment 30 years after their last concussion. The study compared cognitive function in 19 healthy former athletes with a mean age of 60, who sustained their last sports-related concussion in early adulthood, with 21 former athletes with no history of concussion. The brain-injury group performed worse on neuropsychological tests of memory and other cognitive measures, and also showed some signs of abnormal brain activity.

According to the Los Angeles Times article,

The slight deficits resulting from one or two concussions were similar to problems found in patients with the early stages of dementia, although they did not interfere with the daily life of the otherwise healthy men, researchers reported in the journal Brain.

“They were all very functional, working, still playing sports, and really in good health,” said senior author Dr. Maryse Lassonde of the University of Montreal. “It is only when we compare them to people who did not have concussions that the problems come up.”

The problems were relatively minor, but they do send a cautionary note to the military. Post-deployment surveys suggest that 10 to 20 percent of all deployed troops in Iraq and Afghanistan have suffered concussions, largely linked to blasts from improvised explosive devices, or IEDs. The long-term effects of such injuries has been controversial, and the true impact of this wave of brain injuries may not become clear until these troops reach their 60s, but the findings may provide a hint of what’s to come. (For more on blast-related brain injury, see “Brain Trauma in Iraq.”)