Research Summary

At Least 1 in 4 Former NFL Players Who Died in 2016-21 Had CTE, US Study Finds

Anthony Calabro, MA

Key Highlights

  • At least 24.5% of former National Football League players who died from 2016 through 2021 had neuropathologically confirmed chronic traumatic encephalopathy.
  • Among 338 brain donors, 315 (93.2%) had chronic traumatic encephalopathy and 202 (59.8%) had clinician-adjudicated dementia.
  • Stage IV chronic traumatic encephalopathy was associated with a 44% greater risk of dementia among brain donors.
  • Death certificates identified a neurodegenerative disease as a primary or secondary cause of death in only 40.6% of donors with clinician-adjudicated dementia.

At least 1 in 4 former National Football League (NFL) players who died from 2016 through 2021 had neuropathologically confirmed chronic traumatic encephalopathy (CTE), according to a retrospective population-based cohort study published in BMJ. Among brain donors, dementia was common and significantly associated with stage IV CTE.1

Researchers identified 1712 former NFL players who debuted after 1949, played at least 1 NFL game, and died from 2008 through 2021. Of these players, 338 donated their brains for neuropathologic evaluation. Neuropathologists masked to participants’ clinical and playing histories diagnosed and staged CTE, while clinicians masked to neuropathologic findings reviewed medical records and informant-based histories to adjudicate dementia diagnoses.1

The investigators calculated minimum and maximum possible CTE prevalence by comparing confirmed diagnoses among donors with all former NFL player deaths. They used inverse probability weighting to account for measured differences associated with brain donation when evaluating the relationship between stage IV CTE and dementia.1

Study Findings

Among the 1712 former NFL players who died during the full study period, 338 (19.7%) underwent neuropathologic evaluation and 315 (93.2%) had CTE. The possible prevalence at death ranged from 18.5%, assuming only donors with confirmed CTE had the disease, to 98.7%, assuming all non-donors had CTE.1

During 2016-2021, when brain donation was more frequent, 235 of 878 deceased players underwent evaluation and 215 (91.4%) had CTE. These findings established a minimum confirmed prevalence of 24.5% and a maximum possible prevalence of 97.7%.1

Dementia was diagnosed in 202 of 338 donors (59.8%), including 94 of 104 (90.4%) with stage IV CTE. In the weighted, adjusted analysis, stage IV CTE was associated with an increased risk of dementia (risk ratio, 1.44; 95% CI, 1.16-1.78; P<.001).1

Among donors with clinician-adjudicated dementia, 82 (40.6%) had dementia or another neurodegenerative disease recorded as a primary or secondary cause of death.1

Clinical Implications

According to the study authors, the findings indicate that former NFL players had a higher prevalence of CTE at death than previously reported in community-based studies. The association between CTE severity and dementia also suggests that the neuropathologic findings had clinically important manifestations in this donor cohort.

The authors noted that brain donation is nonrandom and may introduce selection bias that inverse probability weighting cannot fully address. They also cautioned that the findings cannot necessarily be generalized to the broader American football community because NFL players experienced substantial exposure to repetitive head impacts.

Expert Commentary

“CTE severity at death is significantly associated with dementia in NFL player brain donors,” the researchers concluded.1

In an accompanying editorial, Tobias Kurth, MD, ScD, and Richard D. Riley, PhD, described the study as “one of the most informative estimates to date” of CTE burden among former NFL players.2 However, they emphasized that the prevalence range represents “plausible bounds under the assumptions made,” rather than a precise estimate for all former players.2

Drs Kurth and Riley called for prospective recruitment and longitudinal follow-up of players, improved measurement of cumulative head impacts, methods for identifying CTE during life, and “continued efforts to reduce avoidable exposure while uncertainty remains.”2

References

  1. Daneshvar DH, Nowinski CJ, Abdolmohammadi B, et al. Prevalence of chronic traumatic encephalopathy at death in National Football League players: retrospective population based cohort study, 2008-21. BMJ. 2026;394. doi:10.1136/bmj-2026-100418
  2. Kurth T, Riley RD. Chronic traumatic encephalopathy in former NFL players. BMJ. 2026;394. doi:10.1136/bmj-2026-100526