The researchers also found that NFL players with ALS had longer careers than those without the disease.
CNN  — 

NFL players are about four times more likely to die of amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease, than the general public, researchers found in a study published Wednesday.

The researchers from Harvard University and Boston University’s CTE Center evaluated all 19,423 NFL athletes who played one or more games between 1960 and 2019, the largest study to date on the relationship between football and ALS. Previous studies had found a similar link between football and ALS but among much smaller numbers of athletes.

In the new study, published in the journal JAMA Open Network, the researchers also found that NFL players diagnosed with ALS had longer professional football careers than those without the disease, suggesting an association between the disease and increased exposure to head trauma. Those who had ALS had an average career of 7 years, compared with 4.5 years among players who didn’t have ALS.

“We believe this novel finding linking a longer career to increased risk of ALS adds to the growing evidence that repetitive head impacts from playing football are contributing to professional players developing ALS,” study co-author Dr. Daniel Daneshvar said in a statement. Daenshvar is assistant professor at Harvard Medical School and a brain injury physician at Spaulding Rehabilitation Hospital.

The researchers combed through public records on all the players between October 2020 and July 2021, including news reports, obituaries and NFL statistics. They found 38 players who received a diagnosis of ALS, of whom 28 had died of the disease.

The overall incidence of ALS in the United States is 1.5 to 2.2 cases per 100,000 people, but the odds go up with age. “Because ALS is a fatal disease with a typically rapid course, its incidence rate largely approximates mortality,” the researchers noted.

ALS is a neurodegenerative disease more likely to be diagnosed in older white men. The root causes are still unknown, and most cases are considered sporadic.

The researchers hypothesized about a relationship between head trauma and ALS because of a similar link detected between football and the neurodegenerative disease chronic traumatic encephalopathy (CTE). Previous research has noted that CTE and ALS may have some similar impacts on the brain.

“In our brain bank, we have found a similar relationship between a longer football career and an increased risk of other neurodegenerative diseases, including chronic traumatic encephalopathy (CTE) and Lewy body disease, which can cause Parkinsonism,” added Dr. Ann McKee, chief of neuropathology at VA Boston Healthcare System and director of the BU CTE Center. “It has become clear that years of repeated impacts to the head can cause the human brain to break down along many pathways.”

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The researchers noted that other potential factors that may affect ALS diagnosis and need to be evaluated include smoking, exercise exertion and pesticide exposure. They also found no relationship between position played, race or age and disease. But they said the number of athletes diagnosed with the disease made it difficult to make any determinations.

The NFL has not responded to a request for comment on the findings.