Aug. 29, 2013 at 3:31 PM ET
From “punch-drunk” boxers to Junior Seau, the NFL player whose family says he committed suicide because of brain injuries, knocks on the head have long been suspected of causing long-term damage in professional sports.
It was only common wisdom and rumor until a few years ago. But Thursday’s decision by the National Football League to settle with 4,500 ex-players over head injuries reflects a growing body of research that shows that repeated concussions can cause permanent brain damage.
Delicate nerves crushed by the recoil from a head impact are not only damaged themselves, they appear to release message-carrying chemicals than can cause nearby nerve cells to die. The cascade of damage can lead to a newly characterized condition called chronic traumatic encephalopathy (CTE).
“I don’t think anyone has truly been able to work out the exact process through which that happens,” says brain expert Dr. Bert Vargas of the Mayo Clinic in Scottsdale, Ariz.
Symptoms can range from dementia, to altered behavior, to, possibly, amyotrophic lateral sclerosis, also known as ALS or Lou Gehrig’s disease – a fatal and incurable condition that gradually paralyzes its victims.
Within seconds of a blow to the head, cells can shut down.
“Scientifically, what we're seeing is there is actually a change in the electrical activity of the brain that can last weeks or months,” says Dr. Neil Martin, chairman of neurosurgery at the David Geffen School of Medicine at UCLA.
Research shows this can lead to depression and even thoughts of suicide, Martin says.
“Although historically a concussion been called a mild traumatic brain injury, we don’t consider any brain injury a mild injury,” Martin told NBC News.
Just last June, a team at the University of Pittsburgh School of Medicine found that concussion can lead to damage in the brain’s so-called white matter that looks very much like the damage caused by Alzheimer’s disease.
Seau killed himself in May 2012, when he was just 43. An autopsy showed he had CTE. His family sued, saying the condition was caused by repeated blows to his head
And it’s not just professional athletes who may be affected.
Louis De Beaumont of the University of Montreal has done a series of studies in recent years showing, among other things, that one single concussion can affect an athlete 30 years later, slowing reaction time, interfering with attention, and dimming memory.
In 2010, Dr. Ann McKee of the University of Boston and colleagues examined the brains of 12 athletes who had died with signs of neurological disease. The men had been diagnosed with ALS as well as CTE, which causes a type of dementia. The autopsies turned up a protein called TDP-43, which is associated with ALS and a certain type of dementia.
The U.S. Centers for Disease Control and Prevention (CDC) found in 2010 that 173,000 teenagers and children are treated every year in U.S. emergency rooms for temporary brain injuries such as concussions.
A U.S. Institute of Medicine committee released a report in 2008 that found concussions could lead to neurological disease later in life. The IOM says the concern is pressing enough to justify broader study into youngsters who play sports. It’s appointed a panel of experts to look at the research and see if even elementary-school players are at risk.
"The other context is, of course, our wounded warriors who have been exposed to improvised explosive devices," Martin says.
"The same provisions should apply for withholding a soldier from combat as apply to withholding an athlete from competition. They are not functioning at 100 percent capacity and they put themselves at risk, and potentially put the other soldiers in their unit at risk."
Some former NFL players are taking part in a live experiment to see if the repeated head-bashing has caused permanent damage. Researchers from the University of California, Los Angeles, have been using brain scans to compare the brains of five former NFL players 45 and older to those of five healthy men of the same age.
They’ve already found, for instance, that former NFL player Wayne Clark has a small amount of buildup in his brain of a protein called tau, which has been linked with Alzheimer’s, although Clark hasn’t noticed any especially worrying symptoms. He only had one concussion during his career with the San Diego Chargers in the 1970s.