Are men who played high school football in Minnesota in the decade after World War II at increased risk of later developing dementia, Parkinson's or ALS compared with non-football playing high school males? Not according to a 2012 study by researchers at the Mayo Clinic.
Comparing the incidence of dementia, PD and ALS in 438 high school football players from Rochester, Minnesota who played the sport from 1946 to 1956  and 140 non-football playing male classmates, researchers found that the football players were not at increased risk of later developing those neurodegenerative diseases.
The results were consistent with those of a 1990 study  of individuals with Alzheimer's disease which also found no association between risk of disease and participation in contact sports, although, as noted in a 2013 paper, that study was limited by a small sample size.
Bigger, Faster, Stronger
The Mayo Clinic researchers were careful to note in the high school football study the many differences between today's high school football players and those of the distant past: while today's players have better equipment, trainers and physicians who are more knowledgeable about concussions, play under rules which prohibit - at least in theory - leading with the head when blocking and tackling, and may be marginally more likely to report concussive symptoms than players from a prior era, they also tend to be larger and quicker, increasing the force of impact, and wear helmets which, while "dramatically different from the marginally protective headgear of the earlier era, do not eliminate concussions and may give them a false sense of protection."
As a consequence, they cautioned that the results of their study, while they could be viewed as "somewhat reassuring to high school players from 50 years ago, ... should give no reassurance to today's players."
While few studies have evaluated repeated concussive head trauma as a purported risk factor for later neurodegenerative disease, the fact that neither of the two studies identified an increased risk of neurodegeneration among participants in contact/collision sports is neverthless noteworthy, especially given the intense media focus in recent years highlighting the purported risk to athletes in contact and collision sports of developing degenerative neurocognitive diseases such as CTE, and studies which seem to correlate increased risk with the length of time engaged in the sport and the number of traumatic injuries.
The lack of studies prompted the most recent international consensus statement on sport-related concussions not only to conclude that, as of yet, "no reasonable basis exists to predict which athletes might be at risk other than perhaps to identify very broadly those involved in sports with exposure to repeated high-impact forces to the head (e.g boxing, American football)."
"As such, the speculation that repeated concussion or subconcussive impacts cause CTE remains unproven," the statement continues. "The extent to which age-related changes, psychiatric or mental health illnesss, alcohol/drug use or co-existing medical or dementing illnesses contributed to this process is largely unaccounted for in the published literature. At present, the interpretation of causation in the modern CTE case studies should proceed cautiously."
Remarkably, the consensus statement concludes with a direct shot at the media, recognizing the importance of addressing the "fears of parents/athletes from media pressure related to the possibility of CTE."
Since the publication of the consensus statement, four additional studies[8-11] have all taken essentially the same position, one highly critical, not just of the media, but of the "scientific reports about CTE to which [such sensational media reports] are connected."
No need to panic
"The last thing we want is for people to panic. Just because you've had a concussion does not mean your brain will age more quickly or you'll get Alzheimer's," says Steven Broglio, Assistant Professor of Kinesiology and Director of the Neurotrauma Research Laboratory at the University of Michigan School of Kinesiology, in speaking in 2012 about a study on which he was lead author which suggests that concussions may speed up the brain's natural aging process.
Broglio stressed that the influence of various lifestyle and environmental factors, such as smoking, alcohol consumption, physical exercise, family history (genetics), whether or not a concussed athlete "exercises" their brain, and even how dense the gray matter in a person's brain is, which gives them greater "cognitive reserve" to draw upon may also impact the brain's aging process, and that "concussion may only be one small factor."
In addition, he said, this line of research is still in its infancy. "'It's not entirely clear," Broglio told the Kalamazoo News, "if and how the brains of young athletes are affected by the sports they play. 'We are realizing it's probably not how many concussions you have that makes a difference, but the total exposure' to concussive and sub-concussive blows."
"What we don't know is if you had a single concussion in high school, does that mean you will get dementia at age 50?" Broglio said. "Clinically, we don't see that. What we think is it will be a dose response.
"So, if you played soccer and sustained some head impacts and maybe one concussion, then you may have a little risk. If you went on and played in college and took more head balls and sustained two more concussions, you're probably at a little bigger risk. Then if you play professionally for a few years, and take more hits to the head, you increase the risk even more. We believe it's a cumulative effect."
Broglio's comments dovetail with those of Tom Talavage, an associate professor of electrical and computer engineering at Purdue, co-director of the Purdue MRI facility, and the lead author in a groundbreaking 2010 study  which found short-term neurocognitive effects among high school football players who sustained a high number of subconcussive hits during the course of a season.
In an April 2011 interview with PBS's Frontline, Talavage said, "A player who stops after his high school career, I wouldn't go so far as to say that [the repetitive subconcussive blows they sustain] will become CTE. Even if a player goes on to college, I wouldn't necessarily say this goes on to become CTE, but I would certainly assume and believe that the risk increases the longer they continue to play and continue to accumulate this number of blows to their head."
Indeed, that seems to be, in the case of soccer, exactly what a 2013 study of 30-year-old amateur soccer players who had been playing the game for many years, appears to show.
No epidemic of early AD
Does the average high school athlete face risks similar to those of former professional football players - such as those whose brains, upon examination after death, show signs of CTE, or who, even if still alive, exhibit signs of serious depression or early-onset dementia which researchers have linked to their years on the playing field?
Broglio says that there is little to no evidence that they do.
"We're not seeing an epidemic of men in their early 50s with early Alzheimer's because they played high school football," Broglio told the Kalamazoo News in 2012.
Which is exactly what the Mayo Clinic researchers reported a year later.
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