In what has been called the largest study of mortality in NFL players to date, neurodegenerative mortality rates were nearly four times higher for former National Football League (NFL) players in comparison to the general population.
For the retrospective study, recently published in eClinicalMedicine, researchers reviewed data from the Sports Reference, LLC database for 19,824 former NFL players with a total of 518,833 person years. All athletes in the cohort made their debut between the years of 1960 to 2019 and played in at least one regular season or post-season game, according to the study. Out of 1,994 decedents, the study authors noted that 178 died from neurodegenerative disease (NDD).
The researchers found that in comparison to the general population, former NFL players had:
• a 3.94-fold higher rate of neurodengenerative mortality overall;
• over a 4.5-fold higher mortality rate for amyotrophic lateral sclerosis (ALS);
• a 3.8-fold higher mortality rate for all-cause dementia; and
• over a 3.8-fold higher mortality rate for Parkinson’s disease (PD).
“Neurodegenerative mortality was nearly four times higher than the general population in this fully enumerated cohort of NFL players, with subtype-specific elevations in dementia, ALS, and PD mortality,” noted lead study author Charlotte B. Luster, BA, who is affiliated with the Department of Physical Medicine and Rehabilitation at the Spaulding Rehabilitation Hospital in Boston, and colleagues.
Former NFL players younger than 60 years of age had a 15.38 higher standardized mortality ratio (SMR) for ALS and a 7.69 SMR for all-cause dementia mortality in comparison to those of similar age in the general population, according to the study authors. The researchers also noted that former NFL players younger than 60 overall had a 3.5-fold higher neurodegenerative mortality rate than former players over the age of 60.
“The 15-fold increased risk of ALS and ∼8-fold risk of dementia mortality in players <60-years-old supports RHI (repetitive head impact) exposure as a driver of earlier NDD pathogenesis. Notably, one of the three dementia decedents <60-years-old died in his forties, and before CTE (chronic traumatic encephalopathy) was widely publicized. These results reinforce evidence of the hazards associated with American football and the link between cumulative RHI exposure and early-onset neurodegenerative mortality,” posited Luster and colleagues.
While secondary analyses revealed no difference between players who played speed positions (non-lineman positions) vs. non-speed players (offensive and defensive linemen) with respect to ALS or PD mortality, the study authors pointed out that former players in speed positions were 67 percent more likely to have neurodegenerative mortality and had more than double the likelihood of all-cause dementia mortality.
Three Key Takeaways
• Neurodegenerative disease mortality risk was disproportionately concentrated in younger former players. Players under 60 had a 15.38-fold higher standardized mortality ratio (SMR) for ALS and a 7.69-fold higher SMR for all-cause dementia mortality compared to age-matched peers in the general population, with overall neurodegenerative mortality 3.5 times higher than in players over 60.
• The study authors attribute elevated risk to cumulative repetitive head impact exposure rather than isolated injury events.
The magnitude of early-onset ALS and dementia mortality was interpreted by the authors as supporting repetitive head impact as a driver of neurodegenerative pathogenesis.
• Position played was associated with dementia mortality but not with ALS or Parkinson's disease mortality.
Speed-position players had a 67 percent higher rate of neurodegenerative mortality and more than double the dementia mortality rate compared to linemen while no positional difference emerged for ALS or PD mortality, indicating the relationship between playing position and neurodegenerative risk was subtype-specific rather than uniform.
The researchers also found a 30 percent lower all-cause mortality rate for former NFL players in contrast to the general population. More specifically, former NFL players had 36 percent and 26 percent lower cancer-related and cardiovascular disease-related mortality rates, respectively, according to the study authors.
“The broader observed NDD-excluded potential survivorship effect aligns with the NFL selection bias for physically fit individuals, as well as the benefits of regular exercise and medical care. Individuals who compete in elite level athletics are more likely to be physically and cognitively high-performing, behaviorally regulated, tolerant of high workloads, and less likely to smoke or have a major injury or disease that prevents exercise, compared to the general population,” noted Luster and colleagues.
(Editor’s note: For related content, see “Molecular Imaging in Focus: Emerging Tau PET Radiotracer Shows Early Promise for CTE Detection in Living Patients,” “MRI Study Reveals Significant Brain Changes in Adolescent Football Players” and “What MRI-Derived Data and Other Factors Reveal About White Matter Hyperintensity in Former Football Players.”)
In regard to study limitations, the authors conceded a lack of data with respect to patient age at the time of NDD onset or diagnosis and the potential for underreporting of neurodegenerative mortality due to frequent misclassification.
