Severe CTE clearly linked to dementia, study finds

Severe CTE is clearly linked to dementia in people exposed to repetitive head impacts, researchers have found.

Chronic traumatic encephalopathy, or CTE, is a progressive brain disorder caused by repeated head impacts.

It is seen in people who play contact sports, serve in the military or are exposed to physical violence.

CTE can only be definitively confirmed after death by examining the brain and is difficult to diagnose during life. It can also be misdiagnosed as Alzheimer’s disease or other forms of dementia.

Dr Amy Bany Adams is acting director of the National Institute of Neurological Disorders and Stroke at the US National Institutes of Health, which funded the research.

She said: “By examining hundreds of brains and ruling out other common neurodegenerative diseases, the team could look at CTE alone and linked it to symptoms reported during life.”

To clarify the link between CTE and symptoms, researchers at Boston University led by Dr Michael Alosco examined brains from 614 donors exposed to repetitive head impacts.

None had neurodegenerative disease diagnoses other than CTE. The team accounted for vascular injury, substance use and age, and gathered information about donors’ mood, behaviour and thinking abilities.

Of the 614 brains, 366 had CTE and 248 did not.

People with more severe CTE, defined as stages III and IV, had worse cognitive and functional symptoms.

Those with stage IV CTE were 4.5 times more likely to have had a dementia diagnosis than those without CTE. In contrast, milder CTE at stages I and II was not linked to dementia, cognitive symptoms or functional symptoms.

Mood and behavioural symptoms were not associated with any stage of CTE, even though these are common among people exposed to repetitive head impacts.

This suggests such symptoms may be caused by other types of brain damage related to repetitive head impacts rather than CTE itself.

Alosco said: “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.”