A person who experiences traumatic brain injuries is more likely to develop dementia – even decades later, according to a new study.
The study, published Tuesday in the journal The Lancet Psychiatry, examined nearly 2.8 million people in Denmark, following them over 36 years. It found that people who had experienced a traumatic brain injury had a 24 per cent higher risk of being diagnosed with dementia than those who had never experienced such an injury.
The risk increased with the number of injuries, said study co-author Jesse Fann, a professor in the department of psychiatry and behavioural sciences at the University of Washington School of Medicine.
“There was a clear pattern between the number of brain injuries a person has and their risk of dementia as well as the severity of the brain injury and their subsequent risk of dementia,” he said.
Because the study was carried out over three decades, it was able to capture people who experienced a traumatic brain injury in their 20s, and see whether they were diagnosed with dementia by their 50s. It found that people with a TBI in their 20s were about 63 per cent more likely to develop dementia 30 years later than people who didn’t get a TBI in their 20s.
“The absolute risk of dementia when a person is in their 50s is still very low. But there was an increased risk,” said Fann.
“This is a solid research study with an impressively large cohort,” said Dr. Tom Schweizer, director of the Neuroscience Research Program at St. Michael’s Hospital in Toronto in an emailed statement.
“This study provides compelling evidence of a link between TBI and dementia, that goes beyond typical studies focusing on professional athletes in contact sports (e.g., football), to include a broader representation of the general public.”
The study only included people who were diagnosed with traumatic brain injuries in hospitals, meaning that people who had milder conditions and were diagnosed by a primary care physician wouldn’t have been counted.
That means that it’s difficult to apply these findings directly to many sports injuries, said Michael Hutchison, director of the concussion program at the David L. MacIntosh Sport Medicine Clinic at the University of Toronto.
It’s relatively rare that athletes lose consciousness when they hit their head, and their injuries tend to be less severe, he said. However, he thinks that this study’s findings indicate a need for further research specific to sports. “They should try to emulate or repeat this type of design in their own environment,” he said.
With that said, “Getting hit in the head is probably not a good thing.”
A growing body of research is showing lots of problems related to these kinds of injuries, and so, it’s reasonable to take common-sense precautions and not engage in risky behaviour, he said.
The results of this study, which show that older people are especially at risk of developing dementia within the first year of a traumatic brain injury, suggest “it is important to evaluate policy and patient management during this time,” said Schweizer. Similarly, more research needs to be done on how to reduce the risks in younger patients, who are also much more likely to develop dementia.
Fann believes that work on things like helmets and traffic safety to prevent injuries in the first place should continue. As well, there should be more research on how to help people who have already experienced an injury.
“If a person has had a brain injury they may want to pay particular attention to other known risk factors for dementia,” he said. Things like obesity and alcohol or tobacco use can be changed, reducing a person’s overall risk.