A new study says CTE should be recognised as a cause of dementia, with those in the most advanced stages facing a 4.5-fold higher lifetime risk.
Chronic traumatic encephalopathy (CTE) is a degenerative brain condition seen in some athletes.
Linked to repeated head impacts, it can cause memory loss, mood changes, poor coordination and suicidal thoughts. Diagnosis is only possible after death.
People with the most advanced CTE were 4.5 times more likely to develop dementia during life than people without CTE, researchers found.
Many former NHL and NFL players have been posthumously diagnosed with CTE, including Junior Seau, Frank Gifford and Ken Stabler.
The study from researchers at the Boston University CTE Center provides what the centre describes as the clearest evidence yet linking CTE to dementia risk.
The centre says these findings indicate CTE should be known as a cause of dementia.
“This study provides evidence of a robust association between CTE and dementia as well as cognitive symptoms, supporting our suspicions of CTE being a possible cause of dementia,” said Dr Michael Alosco, an associate professor of neurology and co-director of clinical research at the BU CTE Center.
“Establishing that cognitive symptoms and dementia are outcomes of CTE moves us closer to being able to accurately detect and diagnose CTE during life, which is urgently needed.”
Researchers studied brain tissue from more than 600 donors, the majority men.
The donors, primarily contact sport athletes, had known exposure to repetitive head impacts, but none had Alzheimer’s disease, Lewy body disease or frontotemporal lobar degeneration.
They found that 366 male donors had CTE. After examining the donor brains, they calculated the odds of developing dementia across CTE stages I to IV.
Donors with stages III and IV had the worst cognitive and functional symptoms, regardless of age or history of substance use treatment.
Lower stages were not associated with dementia, cognitive impairment or functional decline.
The team also found no link between less severe CTE and changes in mood or thinking, suggesting observed changes may stem from other effects of repetitive head impacts or unrelated medical or environmental factors.
“Understanding which brain changes drive cognitive decline is essential,” said Dr Richard Hodes, director of the National Institute of Health’s National Institute on Aging.
“This study shows that only severe CTE has a clear link to dementia, which provides an important distinction for researchers, healthcare providers and families.”
The study also found that dementia due to CTE is often misdiagnosed as Alzheimer’s disease.
Both conditions are marked by abnormal tau proteins that build up in brain cells and affect blood vessels, although the tau differs in each disease.
Of donors with CTE who had received a dementia diagnosis during life, 40 per cent were told they had Alzheimer’s disease but showed no evidence of it at autopsy.
A further 38 per cent of families were told the cause of dementia was unknown or could not be specified.
