American Football Participation Linked to Parkinsonism Risk in People with CTE

Parkinsonism was prevalent among deceased contact sports participants with chronic traumatic encephalopathy (CTE) and was associated with repetitive head impacts (RHIs), substantia nigra (SN) Lewy bodies (LBs), neurofibrillary tangles (NFTs), dopaminergic neuronal loss, and age at death. The results of a cross-sectional study, published in JAMA Neurology, have potential implications for the neurologic consequences of long-term contact sports participation.

A total of 481 male autopsy participants from the Understanding Neurologic Injury and Traumatic Encephalopathy brain bank with a history of RHIs and neuropathologically diagnosed CTE were included in the study analysis. Participants were evaluated for dementia and parkinsonism based on postmortem informant interviews, online surveys, medical records, and self-reported information. Neurologic assessments were conducted to measure nigral data including NFT density, LBs, and neuronal loss.

There were 119 participants (24.7%) who were found to have exhibited parkinsonism during life. Compared to those without parkinsonism, participants with parkinsonism during life were found to:

• Be older at time of death (mean [SD], 71.5 [13.0] years vs 54.1 [19.3] years; P<.001)
• Have higher rates of dementia, visual hallucinations, and probable rapid eye movement sleep behavior disorder (pRBD)
• Have more severe CTE stage, with 29.4% of those exhibiting parkinsonism having stage IV CTE vs 10.8% of those without

In terms of nigral pathology:

• Moderate-severe NFTs were present in 42.7% of participants with parkinsonism, vs 29.9% of those without.
• Moderate-severe neuronal loss was present in 52.1% of participants with parkinsonism, vs 17.1% of those without.
• LBs were present in 24.1% of those with parkinsonism, vs 5.8% of those without.
• Years of contact sports participation were associated with increased SN NFTs and neuronal loss.

Additionally, American football was the more frequent primary sport played by participants with parkinsonism (90.1%) vs those without. Among participants who played American football, SN NFTs and neuronal loss mediated the relationship between years of play and parkinsonism.