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.

New research has linked richer social ties to better cognitive health in older adults, offering new insight into how connection relates to thinking and memory.

Earlier studies found links between specific social factors and health.

This study appears to be the first to build combined social profiles and test how they relate to cognitive health in older adults.

An interdisciplinary team from McGill University and Université Laval created three social environment categories, described as weaker, intermediate and richer.

They assembled 24 social variables such as network size, support, cohesion and isolation using data from about 30,000 participants in the Canadian Longitudinal Study on Aging, a nationally representative cohort of randomly selected Canadians aged 45 to 84 at baseline.

For cognition, the researchers examined three domains: executive function, which involves planning and decision-making; episodic memory, the ability to recall past events; and prospective memory, the ability to remember to perform planned actions.

They used data from a battery of tests previously administered to participants.

Daiva Nielsen is associate professor at the McGill School of Human Nutrition and co-first author of the paper

Nielsen said: “We identified significant associations between the social profiles and all three cognitive domains, with the intermediate and richer profiles generally exhibiting better cognitive outcomes than the weaker profile.”

The researcher noted that the effect size of the associations, a statistical measure of the strength of the relationship between variables, was relatively small, which is consistent with previous studies.

Nielsen noted that the effect sizes were somewhat stronger for participants aged 65 or older.

According to the researcher, this suggests that the social environment-cognition association may be more significant later in life.

Awareness has been increasing of the importance of social connection in public health.

Lack of social connection has been shown to be comparable to more widely acknowledged disease risk factors such as smoking, physical inactivity and obesity.

It is important to translate this knowledge to the public to empower individuals to help build meaningful connections within their communities.” she said.

The authors noted that the observed associations are correlational rather than causal, and it is possible, for example, that poor cognitive health also leads individuals to withdraw from social life.

The team, whose members span marketing, human behaviour, nutrition and epidemiology, hopes to continue using the Canadian Longitudinal Study on Aging data and the newly created social profiles in future research, said Nielsen.

The next steps involve studying changes in social environments and various health-related outcomes, including diet and chronic disease risk, she added.

“This work is an excellent example of the benefits of multidisciplinary research teams that can tackle complex research questions and bring diverse knowledge and expertise.” she said.