Canadian research shows that the effects of head trauma can last for many years after the initial injury.

New research on the impact of traumatic brain injuries in young athletes shows that abnormal brainwaves and atrophy can persist for two years after a concussion.

Research published in the medical journals BrainandCerebral Cortexshows that, along with abnormal brainwaves, young athletes who have concussions can experience deterioration of the nerves that control motor function.

While this damage isn’t always apparent immediately after the injury, the side-effects can persist for decades.

The author of the study, neuropsychologist Dr. Maryse Lassonde, treated hockey players for the Montreal Canadiens for 15 years and has been studying the effects of concussions on hockey players since 1997. Her recent research into the effects of concussions on young and old athletes could have implications for the regulation of professional and youth sports.

“First of all, concussions lead to attention problems, which we can see using sophisticated techniques such as the EEG,” Lassonde said in a press release. “This may also lead to motor problems in young athletes.”

Lassonde’s research joins a growing body of studies on the long- and short-term effects of repeated head trauma, especially on professional athletes and military personnel.

Lassonde also studied the brains of older athletes who suffered their last concussion at least 30 years ago. She compared them to healthy people who hadn’t suffered concussions and found that the head trauma caused lasting effects similar to early symptoms of Parkinson’s disease, including motor, attention, and memory problems.

Her research also indicated that the older athlete’s brains experienced a type of “thinning” that typically occurs in Alzheimer’s patients.

“This thinning correlated with memory decline and attention decline,” Lassonde, who is also the director of the Quebec Nature and Technologies Granting Agency, said.

One previous study examined the brains of a handful of retired professional football players following the death of Junior Seau, who experienced depression, memory loss, and other problems before he committed suicide last year.

Examinations of his brain and those of other players revealed evidence of chronic traumatic encephalopathy (CTE)—a condition seen in many retired NFL players—which has been linked to memory loss, depression, personality changes, progressive dementia, and other serious illnesses.

In recent years, there has been much debate about the level of safety in professional and amateur sports, especially women’s soccer, football, and ice hockey. Many American sports organizations have implemented policies to address head injuries, and they are beginning to reduce the number of concussions.

For example, during the 2011-’12 National Hockey League (NHL) season, there were 128 concussions—a nine percent decrease from the previous season, according to statistics compiled by USA Today. This was also the first year that players were evaluated by a team doctor following a head injury, and the doctor got to decide whether or not a player could return to the ice.

Hockey wasn’t always so “safe.”

In the 1930s, NHL fans would jeer at players who wore helmets. It took the NHL eleven years to mandate helmet-wearing for new players after Bill Masterton, a center for the Minnesota North Stars, died from head trauma during a game in 1968. To date, he is the only player to have died from playing in the NHL.

Even with mandatory helmet use and full padding, the fast pace and testosterone-fueled toughness of professional hockey leave players regularly vulnerable to massive hits. And that’s not including times when they drop their gloves and start wailing on each other to the cheers of fans in the stands.

Though players are tough and can take a hit, the effects of this repeated jarring on the brain are slowly coming to light through medical research.

About 400 former National Football League (NFL) players are suing the league, claiming it failed to protect or even tell players about the potential for long-term brain damage.

Lassonde said that young and old athletes alike should not be allowed to participate in a game until symptoms of their concussion are gone.

“Concussions should not be taken lightly,” she said. “We should also follow former players in clinical settings to make sure they are not aging prematurely in terms of cognition.”