Head to Alzheimer's, the putative link between a football career and neurocognitive diseases

I'm a crazy football-head! I breath, read, feed on everything that relates to football. I beg you to call it Football, not Soccer. Whoever came up with this name should be trialled!!! But I don't take offence easy so you're all excused as long as you keep reading to the end of this post. 

Every Saturday night I sit and watch this football TV show 'Match of the Day' that has been going on forever in the UK.  And as always Gary Lineker, a former football player that needs no introductions, is there with his guest panel criticising/acclaiming the weekend football results, goals, saves, performances, Mourinho's grumpiness :P and the like. The program is just that, a gourmet menu of football for football fans. But there was one specific moment in a random episode where they sat down for a while debating the possible link between a long football career, full of headings (head against ball) and concussions, and the onset of neurocognitive degeneration. Seriously! It got so interesting that time I just wanted to learn more about it. Would it be possible a link between neurocognitive degeneration and a career in football due to constantly heading balls? I had to research about it and I found a number of articles that can shed light on this topic but nothing immediately on heading balls. Surprisingly, I also found out that there's a lot of research emerging on this topic and soon certain observations will mature into consistent conclusions ready for discussion.  

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As I said just now I wasn't able to find many articles immediately relating football head injuries resulting from the recurrent heading of a football ball. In addition, the science out there is still dominated by American institutions and therefore pretty much everything found verses American Football (rugby with medieval plastic armours!!!). These were in my opinion the most interesting pieces I was able to read:

Guskiewicz et al (2005) [1] - Cerebral concussion is a recurrent injury in football but the neurological effects that occur as a result are yet not so clear. Some authors researched the relationship between previous head injuries and the probability of cognitive impairment/Alzheimer's disease by analysing a group of retired professional footballers who had had a previous head injury. After statistical study of the results observed (Chi square statistical test with two degrees of freedom negating a chance relationship) it was concluded that the occurrence of dementia-related syndromes 'may' be triggered by recurrent cerebral injuries resulting from a career in football. Retired players that had experienced ≥3 concussions had five times more prevalence of mild cognitive impairment and 3 times more the number of memory loss episodes. The authors could not establish a clear bridge between the series of concussions and Alzheimer's disease, but were able to hypothesise that for retired professional players who had these injuries Alzheimer's disease was happening earlier when compared to the general American male population.

Omalu et al (2005) [2] -  Case-studies always have their huge limitations, especially if not cross-linked with other more embracing studies to draw the most complete scenario, however, these authors analysed the full autopsy (with comprehensive neuropathological examination) results of a former football player that had been complaining of cognitive impairment, mood disorder and parkinsonian symptoms. The positive link between the long-term neurodegenerative outcomes was established with many cerebral observations (particularly with the presence of diffuse amyloid (protein) plaques - one of the Hallmark's of Alzheimer's disease as due to chronic brain trauma they accumulate as insoluble plaques between neurons, contrarily to what happens in healthy brains where these protein 'pieces' are metabolised and eliminated from the organism [3]. In fact, amyloid-beta plaques can be found in patients just a few hours after traumatic brain injury occurs, and the link between these protein plaques and Alzheimer's disease has been thoroughly studied (check Johnson et al (2010) [4] for an idea on the mechanics of this link). Nevertheless, the most surprising fact considering this player is that there was no family history of Alzheimer's disease and no records of him having had any head trauma outside his football career!!!

Small et al (2013) [5] - Five retired National football League players with ages going from 45 to 73 years old were studied using positron emission tomography (PET) with FDDNP (a molecule that binds to plaques (see [6] for more information on how the process goes mechanically) against five control subjects of comparable age, education and BMI (body mass index). Researchers analysed their PET signals in cortical and subcortical regions and came to the conclusion that, even though the results are for a very limited population and do not come along autopsy validation, FDDNP signals were higher in players in comparison to the healthy control subjects, in all the studied subcortical regions and in the amygdala -  the areas responsible for post-trauma tau deposition. Tau proteins are molecules that stabilise the microtubules in the nerve cells.

Many studies that are now arising on the mechanical damage of the brain have inherent methodological limitations. Hence, they must be taken merely as exploratory research. What does it mean? It means that these studies are merely tentative research studies to build up and interlink initial ideas that down the line will feed the very first dogmas/theories. Add to that a natural 'skepticism' from those who control the riches of the football market/organisation and you'll understand that even within NFL there is still some resistance in accepting the causal relation between consecutive head concussions and early cognitive decline later in life [7]. But the matter of fact is that there is definitely enough substance to at least indicate where the future research should go as results point towards a definitive incidence of cases where this link is scientifically verified and confirmed, as I have just explored above. Moreover, because not all players will immediately reveal signs of chronic traumatic encefalopathy [8] research out there needs to not only expand the range of observed population but also the depth of their scrutinising. For example, an interesting approach is the one taken by Marchi et al (2013) [9] where players were assessed after their matches took place and that allowed concluding that blood-brain barrier disruption occurred even in the absence of concussion, thus supporting the possibility that a long career of heading football balls could be linked to the early onset of Alzheimer's and other neurocognitive diseases.

I hope you've enjoyed today's post. Leave me a few comments or just drop a well-done message!

Any corrections or tips are also welcome.

[1] Guskiewicz, K. M., Marshall, S. W., Bailes, J. et al (2005). "Association between recurrent  concussion and late-life  cognitive impaiment in retired professional football players". Neurosurgery, 57(4), pp. 719-726.

[2] Omalu, B. I., DeKosky, S. T., Mynster, R. L. (2005). "Chronic traumatic encefalopathy in a National Football League player". Neurosurgery, 57(1). pp. 128-134.

[3] Amyloid plaques and neurofibrillary tangles, BrightFocus Foundation, [https://www.brightfocus.org/alzheimers/infographic/amyloid-plaques-and-neurofibrillary-tangles], last updated on the 21st of December 2017, last visited on the 1st of November 2018.

[4] Johnson, V. E., Stewart, W., Smith, D. H. (2010). "Traumatic brain injury and amyloid-beta pathology: a link to Alzheimer's disease?". Nature Reviews Neuroscience,11, pp. 361-370.

[5] Small,  G. W., Kepe, V., Siddhart, P. et al (2013). "PET scanning of brain Tau in retired National Football league players: Preliminary findings". The American Journal of Geriatric Psychiatry, 21(2), pp. 138-144.

[6] Ercoli, L. M.,  Siddarth, P., Kepe, V. et al (2009). "Differential FDDNP PET in non-demented middle aged and older adults". The American Journal of Geriatric Psychiatry, 17(5), pp. 397-406.

[7] Kain, D. J. (2009). "It's just a concussion: The National Football League's denial of a causal link between multiple concussions and later-life cognitive decline". HeinOnline [https://heinonline.org/HOL/LandingPage?handle=hein.journals/rutlj40&div=22&id=&page=], last visited on the 06-Nov-2018, last update unknown. 

[8] Hazrati, L-N., Tartaglia, M. C., Diamandis, P. et al (2013). "Absence of chronic traumatic encefalopathyin retired football players with multiple concussions and neurological symptomatology". Human Neuroscience, 7(222), pp. 1 -12.

[9] Marchi, N., Bazarian, J. J., Puvena, V. et al (2013). "Consequences of repeated blood-brain barrier disruption in football players". PLOS One, 8(3), pp. 1-11.

Post Photo by Kenny Webster on Unsplash

[B] Photo by John Torcasio on Unsplash