Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease, is a progressive neurodegenerative disease that affects nerve cells in the brain and spinal cord. It causes loss of muscle control, paralysis, and eventually death. ALS is more common in athletes than in the general population. Some key points on ALS in athletes:
- ALS occurs in all types of athletes, including football players, soccer players, baseball players, basketball players, hockey players, boxers, and others.
- Male athletes have a higher risk of ALS than female athletes.
- Athletes tend to develop ALS at a younger age than non-athletes.
- The reason for the link between athletics and ALS is not fully understood.
- Possible explanations include repetitive head trauma, strenuous physical activity, performance-enhancing drugs, and genetic factors.
- More research is needed to determine why athletes are at increased risk for ALS.
ALS Overview
ALS is a progressive disease that attacks nerve cells called motor neurons in the brain and spinal cord. Motor neurons control muscle movement. As these neurons degenerate and die, a person loses the ability to control their muscles. Early symptoms include muscle weakness, twitching, cramping, and slurred speech. As the disease advances, muscle wasting occurs and paralysis sets in. Most people with ALS die within 2 to 5 years from when symptoms start.
There are two types of ALS:
Sporadic ALS
This is the most common type, accounting for 90-95% of cases. It occurs randomly with no clearly associated risk factors. The causes are unknown.
Familial ALS
About 5-10% of cases are inherited. This type runs in families and is associated with genetic mutations. Mutations in over 25 genes have been linked to familial ALS.
Currently there is no cure for ALS. Treatment focuses on managing symptoms, maintaining function, and improving quality of life. Riluzole is the only FDA-approved drug for ALS – it modestly prolongs survival.
ALS in Athletes
ALS gained public attention in the 1930s when it affected baseball legend Lou Gehrig. Since then, a body of research has linked ALS to participation in professional and elite-level sports. Key findings include:
Higher Risk in Athletes
Several studies show that top-level athletes have a higher risk of developing ALS compared to the general population:
- Italian soccer players were over 6 times more likely to develop ALS.
- NFL football players had 4 times the risk.
- College athletes had a 3 times higher risk.
The degree of physical activity appears to influence risk. Most research shows a higher incidence in elite, competitive athletes compared to the general public. Recreational athletes do not appear to have a significantly elevated risk.
Type of Sport
ALS occurs more frequently in certain sports:
- American football – up to 6 times higher risk.
- Soccer – up to 5 times higher risk.
- Baseball – up to 2 times higher risk.
Other sports with elevated incidence include basketball, boxing, cycling, golf, hockey, marathon running, rugby, swimming, tennis, and more. The evidence linking ALS to specific sports continues to grow.
Earlier Onset
Athletes tend to develop ALS at a younger age compared to non-athletes. In the NFL, the average age of diagnosis is 55 years old compared to 65 in the general population. Early-onset ALS raises suspicions of a link to athletic careers.
Male Predominance
Up to 97% of athlete ALS cases occur in men. This strong male predominance mirrors the demographics of professional sports and further suggests sports-related risk factors.
| Study | Athlete Group | ALS Risk |
|---|---|---|
| Chio et al 2004 | Italian professional soccer players | Over 6 times higher |
| Lehman et al 2012 | NFL football players | Over 4 times higher |
| Savica et al 2012 | College athletes | 3 times higher |
Theories on Why Athletes Get ALS
There are several theories that attempt to explain the connection between high-level athletics and ALS risk:
Repetitive Head Trauma
Many researchers believe repetitive head injuries play a major role. Sports like football, boxing, hockey, and soccer involve regular trauma to the head and brain. Possible mechanisms include:
- Abnormal accumulation of tau protein.
- Inflammation of glial cells in the brain.
- Disruption of the blood-brain barrier.
Evidence indicates head trauma can trigger progressive neurodegeneration later in life. The brains of athletes with ALS often show signs of chronic traumatic encephalopathy (CTE).
Extreme Physical Exertion
Intense training regimens put significant stress on the body. Some posit that overexertion could contribute to ALS over an athletic career. Possible factors include:
- High metabolic demands on motor neurons.
- Oxidative stress and free radical damage.
- Mitochondrial dysfunction.
- Impaired muscle recovery.
However, moderate physical activity does not appear to increase ALS risk. The link seems specific to extreme and repetitive exertion in competitive athletes.
Performance-Enhancing Drugs
Up to 75% of athletes admit to using banned performance-enhancing substances like steroids and human growth hormone (HGH). These drugs allow training above natural limits. Potential mechanisms include:
- HGH may overstimulate motor neurons.
- Anabolic steroids could cause hormonal imbalances.
- Contaminants or higher than therapeutic dosing.
More research is needed to clarify if performance enhancers contribute to ALS risk. But use is common among athletes and a plausible factor.
Genetic Susceptibility
Genetics may play a role in athlete ALS. Certain genetic profiles could predispose players to neurodegeneration when exposed to sports-related stressors. Variants in genes related to brain trauma, oxidative stress, and metabolic function may interact with athletics to increase risk. More studies are needed on genetic links.
ALS Prevention in Athletes
There are currently no evidence-based guidelines for ALS prevention in athletes. But based on suspected risk factors, possible protective strategies include:
- Limiting head impacts through rule changes and protective gear.
- Carefully monitoring training load and recovery time.
- Banning performance-enhancing substances.
- Restricting return-to-play after concussions.
- Routine neurologic screening exams.
However, these approaches remain speculative and unproven. Overall, more research is urgently needed to understand why athletes develop ALS and how to reduce risk.
Conclusion
In summary, elite athletes across many sports have a consistently higher rate of ALS compared to the general population. The reasons are not fully understood. Leading theories involve repetitive head trauma, intense physical exertion, performance-enhancing drugs, and genetic factors. All likely contribute to some degree. ALS ends athletic careers and lives prematurely. More scientific study is critical to elucidate the link between high-level athletics and ALS so that effective preventive strategies can be developed. Until then, athletes will remain at increased risk for this devastating neurodegenerative disease.