Brain disease linked to boxers and American football players found in homeless people

An illness linked to repetitive head injuries seen in contact sports such as boxing and American football has been found in the brains of people experiencing homelessness for the first time.

Chronic traumatic encephalopathy (CTE) develops after repeated blows to the head often seen in athletes or people who have served in the military. It can be linked to mood swings, aggression, memory loss and movement problems, but can only be confirmed after death by testing for a distinctive build-up of a brain protein called tau.

Researchers from Semmelweis University in Budapest, Hungary, the University of Toronto and Macquarie University in Sydney, Australia, found evidence of the disease in people experiencing homelessness.

They examined 34 post-mortem brains from adults aged 41-67, mostly men. The results found four people had evidence of CTE while two more showed closely related damage. It is the first confirmation of the disease in a European non-athlete population.

First author Dr Krisztina Danics, assistant professor at Semmelweis University’s department of pathology, forensic and insurance medicine, said: “Our focus here was to explore pathological brain changes in a very vulnerable, overlooked group expecting to find early forms of more common conditions such as Alzheimer’s and Parkinson’s.

“It was a surprise to discover CTE in people with no elite sport or military background. This supports the notion that repeated head impacts can add up over a lifetime – even outside stadiums.”

The authors of the study, published in the peer-reviewed Acta Neuropathologica journal, said brain injuries are far more common in homeless people than in the general population, often from falls, assaults, or accidents.

But they added that sometimes violent or aggressive behaviour among people experiencing homelessness may be not only a cause but also a consequence of underlying brain damage.

In the CTE cases, the pattern of brain damage in memory-related regions differed from those seen in Alzheimer’s disease.

Other age-related changes were common across the group, and four cases showed another form of neurological disorder usually seen in later life known as argyrophilic grain disease, even though they were relatively young people.

Before this, similar CTE-related brain changes had been also documented in women in Australia subjected to domestic violence over a long period. 

Dr Gabor G Kovacs, professor in the department of laboratory medicine and pathobiology at the University of Toronto, added: “Seeing CTE in a central European homeless cohort should change the conversation: it’s not only the disease of athletes, and recognising it matters for care, social services, and even how courts think about behaviour and responsibility.”

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CTE first entered medical literature in 1928 in boxers, then drew global attention in 2005 when Dr Bennet Omalu reported it in American football player Mike Webster. Their story was later told in the film Concussion starring Oscar-winner Will Smith, who received a Golden Globe nomination for the role. 

The impact of brain injuries in contact sports has also cast a shadow over UK sport too.

More than 1,100 former rugby players, with 784 from rugby union and 319 from rugby league, have now joined a concussion lawsuit against the sport’s governing bodies, including 2003 England World Cup winners Steve Thompson, Phil Vickery and Mark Regan.

But the new research has shown the need for researchers to look beyond sport.

Now, the next step is to develop better tools to detect this disease during life, since routine MRI scans cannot reveal CTE and people affected by it need to be identified and supported sooner, the international research team said.

“Our focus here was disadvantageous socio-economic status rather than genetics,” said co-author Dr Shelley L Forrest from University of Toronto and Macquarie University. 

“We used strict criteria, including only people who had lived on the street, had no history of professional sport or military service, and whose brains and spinal cords were examined using the same methods – the first such study of a homeless population worldwide. We found CTE in about 12% of the homeless individuals we examined in central Europe.”

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