A 2013 study linking frequent heading of a soccer ball with changes to the white matter of the brain and poorer performance on a neurocognitive test of memory [1] added fuel to the fire of a 30-year-old debate about the effects of heading.
The study by researchers at the Albert Einstein College of Medicine in New York is believed to be the first to quantify subconcussive heading and to assess the association of heading with imaging evidence of brain injury and impaired neurocognitive function.
The findings suggest that may be a heading threshold above which the risk of short- and possibly long-term brain injury dramatically increases.
Establishing such thresholds, the scientists say, could ultimately lead to identification of a 'head count' above which a player's heading should be curtailed for a specific recovery period, an approach akin to the pitch counts implemented in youth baseball to reduce the risk of arm injuries, and an approach that has been proposed by some concussion experts as a way of reducing the risk of long-term brain injury from subconcussive impacts in contact and collision sports.
Researchers at Albert Einstein College of Medicine in New York studied a group of 37 adult, mostly male amateur soccer players, who had been playing soccer for an average of 22 years and reported having played an average of 10 months in the past year, during which they reported heading between 32 and 5,400 times (median of 432).
Looking for subtle signs of traumatic brain injury (TBI) from repetitive soccer heading, they scanned the brains of players using an advanced MRI technique called diffusion-tensor-imaging (DTI) which spots microscopic changes in the white matter of the brain (the long tissue fibers through which messages pass between different areas of gray matter within the brain and spinal cord, likened to the cables that connect individual computers in a network), and had them take a computerized neurocognitive test looking for effects on cognitive function. Their hypothesis was that a threshold for heading exposure would be detectable, above which its association with imaging and neurocognitive abnormalities would significantly increase.
What they found were four different heading thresholds: three (at 885, 1291, and 1558 heads, respectively) above which heading significantly increased the statistical risk of abnormalities in the three different areas (what they called "regions of interest" or ROI) of the white matter of the brain on a DTI measure called fractional anisotropy (FA), [1] and a fourth, higher threshold (1798 heads) linked to poorer neurocognitive performance on a computerized neurocognitive test of memory. Their findings were not significantly associated with prior concussion, yet consistent with findings seen in patients with TBI.
"The relationships detected in this current study ... provide some intriguing clues to pathophysiologic mechanisms," according to the lead author, Michael L. Lipton, MD, PhD, and his Albert Einstein colleagues. "It is well established that most patients with mild TBI recover fully over time, indicating that intrinsic mechanisms [in the brain] are generally able to effect repair of low-level injury. ... Increasing heading exposure up to a threshold, without associated imaging or cognitive changes, may indicate a range of exposure within which these intrinsic injury repair mechanisms are effective. The appearance of significant associations of imaging and cognitive changes with heading above the threshold, on the other hand, suggests that these repair mechanisms may be unable to keep pace with the cumulative injury that occurs beyond this degree of exposure."
Lipton and colleagues said that their findings of lower heading thresholds for increased risk of abnormal changes to the three ROI in the brain and a higher threshold for impaired memory function were expected, and likely reflected a widely recognized epidemiologic phenomenon in which tissue damage precedes damage that impairs day-to-day functioning, and which can be detected on clinical examination without the use of sensitive measures such as DTI or neurocognitive tests.
"Virtually all subjects with exposures exceeding the threshold levels had [significant white matter abnormalities], suggesting that heading above some defined level may be generally unsafe. The important obverse of this finding is that exposure below the threshold level may be generally safe," writes Lipton, although researchers did detect a subset of players who, despite reporting heading numbers below a threshold, nevertheless had white matter abnormalities and impaired memory.
"This pattern suggests that, although exposure below a threshold may be generally safe, some individuals may be particularly sensitive to the effect of subconcussive heading and at higher risk for brain injury and adverse cognitive outcomes after even modest exposure," says the study.
Commenting on the study for MomsTEAM, Frank M. Webbe, Ph.D., Professor of Psychology at Florida Institute of Technology, and an expert on the subject of soccer heading, [2-6, 25] said, "It is not a perfect study by any means, but I believe that their findings are robust with respect to the basic question, 'Does heading a soccer ball relate to impaired white matter integrity in the brain?'" He noted that the findings were consistent with a 2011 study in the Journal of Neurotrauma [7] which found that concussed athletes showed increased FA in DTI compared to control athletes without a history of concussion.
"The current findings that Lipton and his colleagues report extends these findings to an association with subconcussive events. The finding of statistically significant differences in FA among the three heading groups in such a small sample suggests a fairly robust effect. The fact that differences due to heading were observed only with the memory scores among quite a few neurocognitive measures will be seen as problematic by some, since this clearly is not strong support for cognitive deterioration," said Webbe.
"However, I appreciate and agree with the discussion where the authors note that the DTI outcomes indicate an ongoing pathological process which has not yet reached a level where clinical signs are prominent. This is much the same as our current understanding of Alzheimer's disease. There, we now understand that the brain pathology may be present rather early in adulthood, but the insidious changes are not detectable clinically until much later in life," Webbe said.
Indeed, just such a possible link between mild TBI (concussion) and early Alzheimer's is suggested in a June 2013 study by researchers at the University of Pittsburgh Medical Center [23] published in the journal Radiology, which found FA abnormalities in the white matter of the brains of concussed patients related to auditory processing and sleep disturbances, changes resembling in their distribution abnormalities in people with Alzheimer's disease. The study has, however, prompted criticism [2] from concussion and Alzheimer's experts as going too far in trying to draw a link between concussion damage and chronic damage found in Alzheimer's.
Chris Koutures, MD, FAAP, a pediatric and sports medicine physician in Anaheim Hills, California, team doctor at Cal State Fullerton and for the USA National Volleyball Teams, and lead author of the American Academy of Pediatrics' 2010 clinical report on injuries in youth soccer, [21] found the DTI findings "worrisome," but said further studies were "essential to understand the full potential impact of these abnormalities."
"When I read of these results, I immediately thought of the recent study out of UCLA [3] [32] where for the first time, researchers were able to use identify lesions consistent with Chronic Traumatic Encephalopathy in 5 living ex-NFL players (previously, all findings were autopsy-based). Of interest, the players symptoms ranged from significant decline (needed professional and family caretaker assistance) to fairly asymptomatic. It seems once again, the multifactorial, broad spectrum of concussion pathology (e.g. cognitive reserve) is evident."
"Clinically, we use several formats of evaluation in cases of concussion (symptoms [4], neurocognitive testing [5], balance testing [6], physical exam, visual testing [7], radiologic imaging), and it seems that the Lipton study did use neurocognitive testing as another evaluation platform along with DTI. It would be fascinating to see several other types of testing used to better evaluate for issues," Coutures said.
"Characterizing the dose-response curve linking heading and TBI toward understanding threshold effects might facilitate safety guidelines that could help minimize the risk of adverse effects on the brain," Lipton writes. "Prospective monitoring of exposure at the team level, perhaps to be termed head counts, could identify a point at which a player's heading should be curtailed for a specific recovery period, also to be defined through further research. ... [which] is thus essential to develop evidence-based protective strategies that can ensure the future of safe soccer play."
"What can't be directly concluded from this study is the issue of the existence of a frequency 'threshold' above which subconcussive blows are clearly damaging to the integrity of the brain," says Florida Tech's Webbe. "Too many factors are not controlled, including the intensity of the heading episodes, the use of proper technique, the interaction with previous documented concussions, and the biggest to me, idiopathic differences between people with respect to propensity to be concussed. We know that people differ in this regard, but we don't know why. Current work looking at genetic markers and other predisposing factors is critical in this regard."
Webbe said that, "I have a hard time with the threshold idea just from a practical standpoint. There is likely no firm threshold that could be applied to all individuals, so then we get to a statistical prediction where we can predict that N% of individuals who exceed a given threshold will develop brain impairments. It won't matter where the threshold is set, some number of individuals will be affected."
"I am intrigued by this study, and any study that proposes to give some aspect of concrete recommendations for potential overuse or cumulative injury," said Koutures. "Right now, the only real evidence-based recommendations we have to prevent injury are the baseball pitch counts, so I applaud any effort to give more evidence and numbers-based information to help families and medical professionals make more informed decisions."
"With that being said, given the multiplicity of factors that contribute to risk for concussion and the recovery spectrum after a concussion, it may be very difficult to come up with a uniform set of recommendations for preventing head injuries, be it number of headers, number of blows to head on the football field, or even magnitude of blows to head. From professional experience, seems that every person has some form of cognitive threshold (some are higher, some are lower) which once exceeded, can increase the risk for concussion and complicated recovery. Several factors may contribute to a lower threshold (see table at the end of this article), such as history of learning issues/anxiety/depression, past headaches, past concussion, family history of concussion, etc. There are athletes which obvious factors that lower their risk, but many who either we don't appreciate the higher risk or don't have easy to identify higher risk concerns."
"Thus, having a one-size-fits all approach to declaring a heading threshold is in theory a commendable and possibly very useful idea, but in reality, will likely be difficult and impractical to impliment given the amazing heterogenicity of how concussions are caused, how athletes react to concussion, and the short-term and long-term results of suffering a concussion," said Koutures.
"As we see more and more scientific data that reflects true structural, pathological changes in the brain due to heading combined with some level of cognitive change, heading [may] assume[ ] a position in medicine similar to tobacco," suggests Webbe. "We know clearly that some number of people who smoke cigarettes will develop lung cancer and that this number will be much higher than in those who do not smoke. In our society we have chosen not to ban tobacco products as yet, even though everyone is cautioned against smoking."
"I think that it is time to caution against heading until future research shows that it is perfectly safe or until the soccer community accepts that it is a harmful practice, and legislates it out of existence."
The Lipton study is likely to add fuel to the fire of a now 30-year-long debate about soccer heading which, as well-chronicled by Webbe in his 2010 Handbook of Sports Neuropsychology, [2] began in the early 1980's with studies by Alf Tysvaer and his colleagues of retired Norwegian professional soccer players which reported abnormal EEG findings and other neurological, cervical spine, and neuropsychological difficulties. [8-12]
Tysvaer's findings were dismissed at the time as being due to a combination of the fact that the players were using old, heavy balls and their known predilection to drink alcohol. After a study appeared in 1990 [13] that supported Tysvaer's findings, with results that could not be explained away by the type of ball used, a "spate of studies ensued," writes Webbe, "some of which supported findings of neurocognitive impairment in soccer players and some of which did not."
Significantly, however, it was during this period that the "most controversial of Tysvaer's findings" - that neurocognitive deficits were correlated with lifetime frequency of heading soccer balls - received additional support, setting the stage, Webbe says, "for years of confrontational rhetoric over whether heading was causative in neurocognitive impairment" in which the science and politics of soccer intertwined.
The soccer community resisted, he said, reports that suggested difficulty regarding heading, even in the face of growing concern among the scientific community and the media, not just about concussions in soccer, but the risk of brain injury from repetitive heading, with even the scientists becoming embroiled in the controversy; some maintaining that soccer heading had the potential for harm and some saying it didn't.
On one side, Webbe says, is what he loosely refers to as the "soccer establishment," consisting of FIFA, the United States Soccer Federation, England's Football Association (FA), and the various groups advising them. Studies that reported on heading-related concerns and impairment among players were, he says, "dismissed in almost a knee-jerk reaction" by these groups, with heading becoming essentially a "sacred cow within some segments of the soccer establishment." When peer-reviewed, objectively well-done studies showed adverse outcomes of heading [6,14,15], the soccer establishment discounted them in favor of other studies that showed no effects or relationships. [16-18]
But, as Webbe notes, it wasn't just soccer governing bodies that reacted "defensively and aggressively" to studies showing that heading may be systematically injurious to players; many soccer aficionados, players, coaches, parents, and even scientists also, he says, "discounted the science, arguing against some decent studies that heading was a perfectly safe practice." [19]
In addition to the political controversy, Webbe says, the disparity in scientific outcomes - with many studies by capable researchers reporting no relationship between soccer heading and neurocognitive impairment and a "different set of studies by equally capable authors using similar methodologies and similar tests to the first set f[inding] significant relationships between the cumulative and/or seasonal amount of heading and neurocognitive deficits," were difficult to reconcile.
A comprehensive meta-analysis in 2003 [20] identified several methodological issues that it said explained the false positive findings, chief among them the fact that many of studies (as in the current study by the researchers at Albert Einstein) relied upon self-report of the players - which numerous studies have found to be problematic in terms of reliability and validity - while only a very few [4,8] used direct observation.
The most recent findings [33] from a pilot study [9] of retired professional English soccer players found that, once their playing careers end, the chronic low-level head trauma they sustained from repetitive heading did not put them at greater risk of long-term cognitive decline than the general population, but, as with many of the other studies, has since been criticized (by Webbe, among others) as being methodologically flawed.
In his 2010 book, Webbe, suggested two alternative explanations for the inconsistent findings:
First, that heading-related neurocognitive impairment may simply not be very "robust", a hypothesis supported by (a) data demonstrating that the forces that occur during heading are typically less than would be predicted to cause concussions; (b) anecdotal evidence that the vast majority of adult soccer players appear to remain cognitively intact during and after their playing careers, and (c) the absence of known risk factors (other than players putting themselves in a position to challenge for the ball that would predict who would be adversely affected by heading and when; [5] or
Second, that the deleterious effects of heading upon neurocognitive functioning may represent the interactions in repetitive sub-concussive trauma of unknown factors unique to the individual, a hypothesis supported by data from studies showing that soccer players most likely to exhibit lower levels of neurocognitive functioning (and/or, in the case of the current study, exhibiting changes in the white matter of the brain and impaired memory) have been those who headed at relatively high frequencies. [4] Again, this is what the current study found.
As Webbe suggests, and, as the Lipton study appears to confirm, "it may well be that susceptibility to the minor blows associated with heading in soccer players is not a graded phenomenon that distributes across all individuals, but rather is not only idiopathic [i.e. of unknown origin] but also somewhat dichotomous." In other words, as the current study suggests, "some individuals may have significant heading-related difficulties, while others may have none."
As Webbe notes, that this is so should be "no surprise" because identifying the concussion-prone individual in advance is exceedingly difficult. Using American football as an example, two players can seemingly exhibit the same hit but one suffers a concussion and the other doesn't, and we don't know why.
The bottom line, as Webbe concludes, is this: heading-related cognitive impairment due to repetitive sub-concussive blows may occur in relatively few individuals, but whatever the reason, the "clinical response is the same": to determine who is prone to injury from repetitive heading and intervene to prevent further damage."
So what, then, about soccer heading in youth? Not surprisingly, no consensus has emerged in this arena, either in terms of whether the science supports the view that the cumulative effects of heading has adverse neuropsychological consequences or as to when it is safe for children to begin heading.
On the science, a 2010 study [10] by the American Academy of Pediatrics' Council on Sports Medicine and Fitness Executive Committe[21] suggested, perhaps prematurely in light of the Lipton study, that the "contribution of purposeful 'heading' of the soccer ball to both acute and potential long-term concussive effects, such as cognitive dysfunction, seems less controversial today, as previously." At the time, it concluded that a critical review of the literature "does not support the contention that purposeful heading contacts are likely to lead to either acute or cumulative brain damage, and additional study is necessary to provide confirmatory evidence of neuropsychological consequences of subconcussive soccer-related head contacts."
A 2012 study [11] [22] by researchers at the Cleveland Clinic concurred, concluding, after reviewing theoretical concerns, the results of biomechanical laboratory experiments, and then-available clinical data regarding the effects of chronic, subconcussive head injury from soccer heading, that there was "no support" in recent studies for the findings of the early Norwegian studies, asserting that more recent studies failed to show that soccer players experience neurocognitive impairment compared with athletes in other sports, or that more frequent headers scored more poorly on sophisticated neuropsychiatric evaluation than less frequent headers.
This is exactly what the Lipton study did find, although, to be fair, the Cleveland Clinic researchers were quick to caution that damage building up over the long term could not be ruled out. The authors thus urged "players, parents, and coaches [to] be aware that although laboratory studies indicate that ... any possible detrimental effect from repetitive subconcussive heading may only become clinically evident decades into the future."
As is so often the case in head injury research, pediatric studies on the effect of cumulative soccer heading on the brains of children are few and far between, with only a handful of studies providing data on heading in youth soccer. [24-26] Similar to the studies on adults, the outcomes are contradictory. [2] The issue, however, as Webbe notes, is "not trivial," citing a 2009 study of which he was a co-author [25] which found that almost 50% of a sample reported concussion-like symptoms [4] (headache, dizziness, balance problems) after heading a soccer ball, similar to post-concussion reports from adolescent and Olympic soccer athletes. [27]
Webbe suggests that, as in adult soccer, politics regarding heading leads some coaches and parents to be reluctant to participate in a study because it might "deter children from heading behavior and competitiveness in the sport."
As Florida Tech's Webbe notes in his 2010 book, [2] "Generally speaking, there is general consensus that proper heading technique requires strong neck muscles to form a stable platform bridging the body and head."
A just-published 2013 study [12] [28] found that balanced neck strength may reduce the acceleration of the head during the act of heading a soccer ball, thus reducing the risk of brain injury from such low-grade, subconcussive hits. "Achieving and maintaining a balance in neck strength may be a key preventative technique in limiting acceleration, hence limiting the potential risks of repetitive heading in soccer," writes lead author Zachary D.W. Dezman, M.D., a resident in the University of Maryland School of Medicine Department of Emergency Medicine.
But the importance of neck strength is where the consensus ends. Some experts, most notably Robert C. Cantu, M.D., in his 2012 book, "Concussions and Our Kids," [29] recommend that soccer heading be delayed until age 14, not just because of the risk of repetitive brain trauma but because "so much happens when a young player springs into the air expecting to meet the ball with her forehead, and so much of its results in head trauma [e.g. concussions]. Head meeting ball is the scenario of least concern. Problems arise when head meets shoulder, elbow, or another head."
Such concerns have led some soccer programs, including AYSO, with 650,000 participants, to recommend against heading in soccer before age 10. [30] Other national soccer programs have not, however, followed suit.
The AAP recommends that heading of the ball only be taught when the child is old enough to learn proper technique and has developed coordinated use of his or her head, neck, and trunk to properly contract the neck muscles and contact the ball with the forehead, [21] a position similar to that recommended by the University of Maryland's Dezman in the 2013 study on neck strength in soccer. [27] "Balancing muscles may be particularly beneficial," writes Dezman, "for younger players learning the game and would perhaps be a more objective, quantitative parameter when deciding when to introduce heading," rather than strict age limits.
In the other camp are those, like Dr. William Meehan, Director of the Sports Concussion Clinic and Micheli Center for Sports Injury Prevention at Boston Children's Hospital, and author of Kids, Sports and Concussions, [31] who don't think there should be any age limits on heading and believe delaying the teaching of heading "would be a mistake. As children become stronger and better coordinated, they are able to kick the ball at a much greater velocity. It seems unwise," he writes, "to have their first time trying to head a ball occur at an age when the ball can be kicked with significant speed and force."
"Instead," Dr. Meehan suggests, "using smaller, softer balls that weigh less while children are younger allows them to develop the skills necessary for proper heading of the ball. This seems like a safer approach. They can learn proper technique, develop strength, and master the timing and coordination necessary for proper heading of the ball when young, before they begin to play with an adult-size ball that can be kicked with significant force." Learning to head with a dry, soft, foam ball may be another useful way to start, he says. In this recommendation, he finds support from the American Academy of Pediatrics ' 2010 clinical report, [21] which, while recognizing proper technique as "foremost in reducing the risk of concussion from heading the ball," also says that it "is imperative that soccer balls be water-resistant [one of the supposed culprits in the brain damage found in the retired Norwegian players], sized appropriately for age, and not hyperinflated."
"After reviewing this study (and discussing it with colleagues), there is definite interest in the findings, and a desire to have more information (larger sample size, perhaps even studies of child and adolescent athletes)," said Koutures, lead author of the AAP's youth soccer study. "Does it alone make me want to restrict heading or express more caution? Not quite yet, though I have brought it up in clinical conversations when discussing risks/benefits of soccer with young patients and their families."
"Many of my discussions about sport safety (and head injuries in particular) revolve around acceptable risk, risk tolerance, what we know and do not know about the injury in question, potential risk reduction techniques (helmets, not heading, switching to a non-heading position), and alternatives (less risky activities). There may be contexts where this study carries more impact (perhaps a child with underlying memory issues) and the family may place more weight on the results in making the best decision for their child."
Where does all of this lead parents? In answering the question, "Should my child head soccer balls?" Webbe proposes in his 2010 book [2] the use of the following "decision tree":
Should My Child Head Soccer Balls?
If Yes to ALL: OK with Caution |
If Yes to ANY: NO |
13 or older |
Under 13 |
Proportional musculature for head size |
Large head relative to body |
No history of head injury | Positive history of head injury |
Has had technical heading instruction from a qualified coach |
No technical heading instruction from a qualified coach |
No history of learning or attention problems |
Positive history of learning or attention problems |
As is always the case, it is ultimately up to parents to decide what is best for their child.
1. Lipton M, Kim N, Zimmerman M, Kim M, Stewart W, Branch C, Lipton R. Soccer Heading Is Associated with White Matter Microstructural and Cognitive Abnormalities. Radiology 2013;DOI:10.1148/radiol.13130545.
2. Webbe, FM, & Salinas, C. (2010) The relationship of soccer heading and neuropsychological functioning: When Science and Politics Collide. In F.M. Webbe (Ed.). Handbook of Sport Neuropsychology (pp. 275-294). New York: Springer Publishing Company.
3. Webbe FM. (2006). Definition, physiology, and severity of cerebral concussion. In R. J. Echemendia (Ed.), Sports neuropsychology: Assessment and management of traumatic brain injury (pp. 45-70). New York: The Guilford Press.
4. Webbe, FM. & Ochs, SR. Recency interacts with frequency of soccer heading to predict weaker neuro-cognitive performance. Applied Neuropsychology. 2003;10:31-41. [For article on this study, click here [13]]
5. Webbe FM. & Ochs SR. Personality traits related to heading frequency in male soccer players. J Clin Sp Psychol 2007;1:379-389.
6. Witol AD. & Webbe FM. Soccer heading frequency predicts neuropsychological deficits. Arch Clin Neuropsychol 2003;18: 397-417.
7. Henry C, Tremblay J, Tremblay S, Lee A, Brun C, Lepore N, Theoret H, Ellemberg D, Lassonde M. Acute and Chronic Changes in Diffusivity Measures after Sports Concussion. J Neurotrauma 2011;28(10): 2049-2059.
8. Tysvaer A, Storli O. Association football injuries to the brain: A preliminary report. Br J Sports Med 1981:15:163-166.
9. Sortland O, Tysvaer A. Damage in former association football players: An evaluation by cerebral computed tomography. Neuroradiology 1989;31:44-48.
10. Tysvaer A, Storli O, Bachen N. Soccer injuries to the brain: A neurologic and electroencephalographic study of former players. Acta Neurologica Scandinavica. 1989;80:151-156.
11. Tysvaer A, Lochen E. Soccer injuries to the brain: A neuropsychologic study of former soccer players. Am J Sports Med 1991;19:56- 60.
12. Tysvaer A. Head and neck injuries in soccer: Impact of minor trauma. Sports Medicine 1992:14:200-213.
13. Abreau F, Templer D, Schuyler B, Hutchison H. Neuropsychological assessment of soccer players. Neuropsychology 1990;4:175-181.
14. Matser J, Kessels A, Jordan B, Lezak M, Troost J. Chronic traumatic brain injury in professional soccer players. Neurol 1998;51: 791-796.
15. Matser J, Kessels A, Lezak M, Jordan B, Troost J. Neuropsychological impairment in amateur soccer players. JAMA 1999;282: 971-973 (amateur soccer players found to have diminished ability on tests of memory and planning).
16. Barnes B, Cooper L, Kirkendall D, McDermott T, Jordan B, Garrett W. Concussion history in elite male and female soccer players. The
Am J Sports Med 1998;26:433-438.
17. Guskiewicz K, Marshall S, Broglio S, Cantu R, Kirkendall D. No evidence of impaired neurocognitive performance in collegiate soccer
players. Am J Sports Med 2002;30(2):157-162.
18. Kirkendall D, et al. Heading in soccer: Integral skill or grounds for cognitive dysfunction? J Ath Tr 2001;36:328-333.
19. Spear,J. Are professional footballers at risk of developing dementia? Int'l J Geriatric Psych 1995;10:1011-1014.
20. Rutherford A, Stephens R, Potter D. The neuropsychology of heading and head trauma in association football (soccer): A review. Neuropsychol Rev 2003;13:153-179.
21. Koutures C, Gregory A, and The Council on Sports Medicine and Fitness. Injuries in Youth Soccer. Pediatrics 2010;125:410-414.
22. Spiotta A, Bartsch A, Benzel E. Heading in Soccer: Dangerous Play? Neurosurgery 2012;70(1):1-11.
23. Fakhran S, Yaeger K, Alhilali L. Symptomatic White Matter Changes in Mild Traumatic Brain Injury Resemble Pathologic Features of Early Alzheimer Dementia. Radiology 2013. DOI:10.1148/radiol.13122343.
24. Janda D, Bir C, & Cheney A. An evaluation of the cumulative concussive effect of soccer heading in the youth population. Injury Control and Safety Promotion 2002;9(1), 25-31.
25. Salinas C, Webbe F, & Devore T. The epidemiology of soccer heading in competitive youth players. J Clin Sport Psychol 2009;3:1-20.
26. Stephens R, Rutherford A, Potter D, & Fernie G. Neuropsychological impairment as a consequence of football (soccer) play and report on school students (13-16 years). Child Neuropsychol. 2005;11:513-526.
27. Barnes B, Cooper L, Kirkendall D, McDermott T, Jordan B, & Garrett W. Concussion history in elite male and female soccer players. Am J Sports Med 1998;26:433-438.
28. Dezman Z, Ledet E, Kerr H. Neck Strength Imbalance Correlates With Increased Head Acceleration in Soccer Heading. Sports Health: A Multidisciplinary Approach 2013; 20(10). DOI: 10.1177/1941738113480935 (published online ahead of print March 20, 2013)(accessed March 21, 2013).
29. Cantu R (2012). Concussions and Our Kids New York: Houghton Mifflin Harcourt
30. Oulette J. Is heading safe? http://www.ayso.org/resources/safety/is_heading_safe.aspx [14]. (accessed March 20, 2013).
31. Meehan WP, III, (2011). Kids, Sports & Concussion. Santa Barbara: Praeger
32. Small G, Kepe V, Siddarth P, Ercoli LM, et al PET Scanning of Brain Tau in Retired National Football League Players: Preliminary Findings. Am J Geriatr Psych 2013;21:138-144.
33. Van Jones SA, Breakley RW, Evans PJ. Heading in football, long-term cognitive decline and dementia: evidence from screening retired professional footballers. Br J Sports Med. 2014;48:159-161, doi:10.1136/bjsports-2013-092758.
Links:
[1] http://en.wikipedia.org/wiki/Fractional_anisotropy
[2] http://www.webmd.com/brain/news/20130618/concussion-damage-looks-much-like-early-alzheimers-study
[3] https://mail.momsteam.com/node/5742
[4] https://mail.momsteam.com/node/149
[5] https://mail.momsteam.com/node/801
[6] https://mail.momsteam.com/node/221
[7] https://mail.momsteam.com/node/6204
[8] https://mail.momsteam.com/node/3289
[9] https://mail.momsteam.com/node/6961
[10] https://mail.momsteam.com/node/544
[11] https://mail.momsteam.com/node/4465
[12] https://mail.momsteam.com/node/5919
[13] https://mail.momsteam.com/node/526
[14] http://www.ayso.org/resources/safety/is_heading_safe.aspx
[15] https://mail.momsteam.com/health-safety/heading-in-youth-soccer-debate-continues
[16] https://mail.momsteam.com/heading/heading-in-soccer-long-term-effect-remains-unclear
[17] https://mail.momsteam.com/heading/stronger-necks-may-reduce-brain-trauma-from-soccer-heading-study-says
[18] https://mail.momsteam.com/sports/soccer/studies-suggest-repeated-heading-of-soccer-balls-effects-short-term-mental-performance
[19] https://mail.momsteam.com/sports/soccer/safety/florida-tech-studies-raises-concerns-for-parents-about-soccer-heading
[20] https://mail.momsteam.com/sports/soccer/two-studies-suggest-soccer-heading-may-lower-test-scores
[21] https://mail.momsteam.com/concussive-and-subconcussive-blows-may-speed-up-brain-natural-aging-process-studies-suggest
[22] https://mail.momsteam.com/sub-concussive/sub-concussive-hits-growing-concern-in-youth-sports
[23] https://mail.momsteam.com/soccer-heading-subconcussive/heading-in-soccer-doesnt-lead-long-term-cognitive-decline-study-finds