Should Johnny play linebacker?

Concussions sustained in high school sports may put young athletes at increased risk for Alzheimer's disease.

By Robert Burton

Read more: Sports, Health, Neurology, Robert Burton, Brains, Mind Reader, Environment & Science

Hard hits in high school football have neuroscientists worried about the long-term impact.

Jan. 13, 2009 | Football isn't a contact sport, it's a collision sport. Dancing is a contact sport. — Vince Lombardi

Last October, a 17-year-old Montclair, N.J., linebacker collapsed following a routine tackle. A month earlier, he had sustained a mild concussion but had recovered and been cleared to play. This time, though, when he stood up on the field, he collapsed again. He died three days later of an acute brain hemorrhage.

Fortunately, such disasters are rare. In 2007, according to the National Center for Catastrophic Sports Injury at the University of North Carolina, only three deaths were attributed to head injuries among the 1.8 million U.S. teenagers playing high school football. On the other hand, it's conservatively estimated that high school and college athletes annually sustain at least 300,000 concussions, or "dings."

Add the growing number of kids playing soccer, hockey, lacrosse and extreme sports, and the concussion rate is staggering. But youth is about taking risks and proving oneself, not about trying to avoid life. Being KO'd or having your bell rung is a rite of passage, proof that you can take whatever is dished out. Parents be damned; let the games begin.

A timeout may in order, however. In the past few years, long-term studies suggest that seemingly uncomplicated concussions, like those sustained in high school sports, may put an athlete at increased risk for Alzheimer's disease. Is this a real and well-established association, or just scare mongering?

A concussion -- often referred to as a mild traumatic brain injury -- is generally defined as a blow to the head followed by transient alterations in mental state ranging from confusion, disorientation and short-term memory defects to an actual loss of consciousness of less than 30 minutes in duration. Traditionally, concussion is divided into degrees of severity based on the duration of posttraumatic amnesia: the failure to accurately recall events that occur subsequent to the head injury. It's generally accepted that a mild concussion results in less than 30 minutes of amnesia, a moderate concussion causes 30 minutes to 24 hours of amnesia, while with a severe concussion, the amnesia persists for greater than 24 hours.

Fortunately, the vast majority of minor concussions clinically resolve themselves within a short time, ranging from a few minutes to a few days to a week. Follow-up neuropsychological testing rarely demonstrates any residual cognitive problems in otherwise healthy young athletes. As a result, minor concussions have been considered self-limiting and without any significant long-term risk. Until now.

Perhaps the best place to begin is with a systematic review of the medical records of a group of 548 veterans who sustained a moderate or severe concussion during World War II. Over the subsequent 40 years, the incidence of Alzheimer's disease in the moderate concussion group was twice the rate in those soldiers without a prior head injury. Those with a severe concussion had a risk four times that of the control group. The effect of minor concussion was not adequately assessed in this study.

In 2003, an editorial in the Journal of Neurology, Neurosurgery, and Psychiatry opined that, at least in males, the risk of Alzheimer's in patients with mild traumatic brain injury was sufficient to advise head-injured patients of the risk of further injuries.

In 2005, scientists at the National Center for Catastrophic Sports Injury tested more than 2,500 retired professional football players. Those with three or more concussions were five times as likely to have cognitive declines classified as mild cognitive impairment, and three times as likely to have significant memory problems as retirees without a history of concussion. Although the researchers didn't find a definite association between recurrent concussion and Alzheimer's disease, keep in mind that the majority of patients with mild cognitive impairment eventually progress to full-blown Alzheimer's. As tentative supporting evidence, the researchers observed an earlier onset of Alzheimer's in the retirees than in the general American male population.

Again, these findings were seen in athletes with a minimum of three concussions; one or two concussions did not have any clearly increased risk of subsequent cognitive impairment.

How brain injuries might predispose someone to Alzheimer's disease remains conjectural. It's clear that significant forces are required for a concussion. An ongoing study at the University of North Carolina found that the impact magnitude of hits delivered by youth hockey players aged 13 to 15 was similar to that experienced by college football players. The average head impact among the youth hockey players was around 20 Gs, but some surpassed 100 Gs -- the forces sustained by a car-crash dummy when a car traveling at 25 mph smashes into a brick wall.

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