Can Football Cause ALS? A Look at the Research

This week, former San Francisco 49ers receiver Dwight Clark announced he has ALS. He joins other NFL football greats including Steve Gleason, Tim Shaw, Kevin Turner, O.J. Brigance, and others, who have been diagnosed with ALS following their pro football careers. These announcements have brought much attention to the connection between football and traumatic brain injury (TBI) and the question of whether such injuries from football can lead to ALS or chronic traumatic encephalopathy (CTE). Here, we highlight some research behind the possible connection.

Traumatic brain injury can be defined as “an alteration in brain function and consciousness which results in impaired cognitive and physical functioning caused by external force.” Traumatic brain injury is not a rare event and can be caused by multiple types of impact to the brain. It is important to note that not all TBI leads to neurodegenerative disease. That said, TBI involves a complex physiological process with both short and long-term outcomes, including increased risk of people developing neurodegenerative diseases such as Alzheimer’s disease, CTE and ALS.

Sometimes there is confusion of whether a person has ALS or CTE, but they present differently. ALS is caused by death of motor neurons (i.e. a type of cell of the central nervous system that coordinates movement). When motor neurons die, they can no longer connect and communicate with muscle, leading to muscle atrophy, weakness and eventually paralysis. Some cases of ALS are also connected to reduced cognitive function due to overlap with Frontotemporal Dementia (FTD). On the other hand, CTE primarily manifests with signs of dementia and cognitive defects. Symptoms can include aggression, depression, impulsivity, irritability, short-term memory loss and heightened occurrences of suicide.

Diagnosis for both ALS and CTE is difficult. On average, it takes one year for an ALS diagnosis, due to the complexity of the disease and possible overlap with similar neurodegenerative disorders. Currently, CTE is only definitively diagnosed after death, by studying brain tissue during autopsy. There is also debate of whether repetitive trauma or even a single TBI is sufficient to cause ALS and CTE. In addition, little is known regarding what type of head trauma causes ALS and CTE. Reports of injury during soccer, football and boxing are the most well reported cases. There is also the possibility that other parts of players’ athletic training experience, not just head trauma, are a risk factor for developing ALS.

Research behind TBI supporting a connection between ALS and CTE is still unclear. A recent study in animal models demonstrated that repeated, mild TBI induced long-lasting defects in motor function and brain pathology. In contrast, a recent study in people with ALS, with and without head injury, showed that “head injury was not associated with faster ALS disease progression” and did not result in a specific pathology in the brain.

Due to the high complexity of both diseases, more long term studies are needed for a full understanding of this connection. Specific TBI biomarkers will be necessary to improve the accuracy of the differential diagnosis between ALS and CTE.

The ALS Association is committed to unlocking these questions to provide these important answers and to providing the best care available to people living with ALS. We also encourage football leagues, from young divisions to the NFL, to continue efforts to make playing football safer to help prevent TBI from occurring in the first place. We will update the ALS community with future studies along these lines.


Traumatic brain injury: a risk factor for neurodegenerative diseases.
Gupta R, Sen N.
Rev Neurosci. 2016 Jan;27(1):93-100. doi: 10.1515/revneuro-2015-0017. Review.
PMID: 26352199

A model of recurrent concussion that leads to long-term motor deficits, CTE-like tauopathy and exacerbation of an ALS phenotype.
Thomsen GM, Ma AM, Ko A, Harada MY, Wyss L, Haro PS, Vit JP, Shelest O, Rhee P, Svendsen CN, Ley EJ.
J Trauma Acute Care Surg. 2016 Dec;81(6):1070-1079.
PMID: 27602892

Head injury does not alter disease progression or neuropathologic outcomes in ALS.
Fournier CN, Gearing M, Upadhyayula SR, Klein M, Glass JD.
Neurology. 2015 Apr 28;84(17):1788-95. doi: 10.1212/WNL.0000000000001522.
PMID: 25832660

A blow to the head trauma – ALS hypothesis.
Armon C, Albert SM.
Neurology. 2015 Apr 28;84(17):1728-9. doi: 10.1212/WNL.0000000000001528. No abstract available.
PMID: 25832659

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3 thoughts on “Can Football Cause ALS? A Look at the Research”

  1. Yes I do believe that football can cause ALS/MND. But not by the bouncing of ball on the head.? All sports can cause this disease by forcing our bodies to the limit. Also hard physical work and taking part in Army duties such as war. jockeys and horse trainers have also been the victim of this disease. At one time – it was suspected that there was an Equine connection. I also believe that the brain still sends the message, but the neurons are dead and there is nothing to migrate them to the muscles. There is another group of neurons that do not die. Such as – the sense of touch. That touch message from a paralysed limb will go back to the brain. This is solely my belief.! From someone who has experience the disease for the past 40 years? 🙂


  2. I have a hypothesis for scientists to study regarding the causes of ALS. I started thinking about this as an elderly neighbor of mine was recently diagnosed with ALS. I started looking at some of the facts and research online and tried connecting the dots to possible causes.

    I read that there is a higher incidence in football and soccer players, men, older aged people, and military veterans (no matter what branch and served in war or peacetime, but with the highest incidence in those who served in the first gulf war.)

    My neighbor and I both love to garden and I was actually bringing her an Easter flower when I learned of her ALS. Her whole yard is full of flowers and she offered to let me take a few. As we entered the gate to her backyard it was like the Secret Garden, color everywhere. She told me she spent a lot of time working on her garden when she was younger. As I returned to my yard and continued digging holes in the soil for my new plants, I kept thinking about what could cause ALS and what connection my neighbor had with football, soccer, military, etc., if any. I couldn’t think of anything, but the more I dug in the soil, something dawned on me. One thing these have in common is a tendency to be outside near soil and grass. Then I did a little bit of Internet research.

    I asked myself what it was that connects all military personnel, no matter what branch, no matter peacetime or war, and the first thing popping into my mind was BOOT CAMP. I found plenty of pictures of recruits doing push ups on manicured lawns or crawling through mud on their bellies, sometimes completely covered in it, or through long grass with their weapons. Similarly, football and soccer teams spend a lot of time on the manicured fields, not only playing their games, but also doing their exercises, not to mention all the neighborhood, etc., fields they may have played and practiced in, contaminated with who knows what, leading up to their careers. Also, whatever treatments are on the grass or pollutants in the soil, will also get tracked home on bottoms of shoes and into houses where there is further invisible contamination.

    I also asked myself what was different about the first gulf war and I kept thinking of the burning oil in Kuwait and all the air and ground pollution that caused. Then I stumbled across something in my research I never realized before. Petroleum is in synthetic fertilizers, pesticides, and insecticides, as well as a bunch of other products I never would have guessed. I started wondering what kind of soils, fertilizers, etc., my neighbor had used in her garden and about just how much of whatever she had used had accumulated in her yard over the years, and possibly bioaccumulated in her body.

    Then I remembered something else. Her next door neighbor had told me a few years ago that this neighbor had told her about a certain fertilizer she swore by that came from cows. I had even gotten some to try. Then it occurred to me, cows eat grass. Had this grass also been treated with herbicides, pesticides, fertilizer, etc.? So I looked that up, sure enough, quite possibly. I also stumbled across something else, many cows are fed corn. This corn is also very likely contaminated with petroleum based fertilizers and pesticides. The sources, whether from cow based fertilizers or not, and the bioaccumulation possibilities seem endless.

    So, there you have it, my hypothesis is: Are ALS genetic mutations are caused by or exacerbated by environmental toxin bioaccumulation in the body, most likely petroleum, and similar toxins that are found in contaminated soil, fertilizer, grass, pesticides, insecticides, herbicides, air, water, and countless other products? And do more sources of exposure, and greater time of exposure of petroleum and similar toxins to the body, is there a greater proportional risk factor to trigger mutations in genes, etc., that lead to ALS?

    The simple research information I obtained on the Internet can easily be googled to verify. I am not a scientist so please forgive any technicalities I may have erred in, but I sincerely hope that the information contained here will trigger some insight into further research to help with the causes and cures for ALS. My thoughts and prayers are with all those affected by this disease.


  3. Now im worried. Maybe i shouldn’t let my 13 year old play what he loves. Might the positions those specific players played, make a difference?


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