A team from the University of Washington has found that the risk of dementia is significantly higher for people with a history of traumatic brain injuries (TBI) than for people with no history of TBI.
The researchers reviewed the history of approximately 2.8 million cases in Denmark and found that the overall risk of dementia for those with a history of dementia was 24 percent higher than those without a history of brain injuries, after accounting for other risk factors for the disease.
The study included 36 years of follow-up, as well as access to a uniform healthcare system that tracks the number and severity of TBIs.
A single traumatic brain injury characterized as severe increases the risk by 35 percent, while a mild traumatic brain injury or concussion increased the risk by 17 percent. The researchers found that the risk of dementia increased by 33 percent for two or three TBIs, 61 percent for four injuries and 183 percent for five or more injuries.
“What surprised us was that even a single mild TBI was associated with a significantly higher risk of dementia,” lead author Jesse Fann, a professor of psychiatry and behavioral sciences at the University of Washington School of Medicine, said in a statement. “And the relationship between the number of traumatic brain injuries and risk of dementia was very clear…similarly, a single severe brain injury seems to have twice the risk associated with dementia as a single mild traumatic brain injury.”
The researchers also discovered that a brain injury in your 20s increases the risk of developing dementia in your 50s by 60 percent.
“Severe TBI is particularly frequent in young people, and it is concerning that the risk of dementia is particular high in relatively young persons who suffer TBI,” co-author Jakob Christensen, an associate professor of neurology at Aarhus University Hospital in Denmark, said in a statement.
Dementia affects 47 million people worldwide and the number of patients is expected to double in the next 20 years. Every year, more than 50 million people worldwide experience a TBI, which occurs when an external force disrupts the brain’s normal function.
Among the nearly 2.8 million people observed in the study, 4.7 percent had at least one TBI diagnosis. Among first TBI diagnoses, 85 percent had been characterized as mild and 15 percent had been characterized as severe or skull fracture. From 1999 to 2013, 4.5 percent of the patients over age 50 years developed dementia, of those, 5.3 percent had sustained at least one TBI during the observation period, which began in 1977. The mean age at first diagnosis of dementia was 80.7 years.
Men with TBI histories developed dementia at a 30 percent rate, while women had just a 19 percent rate.
According to Fann, most people who sustain a single concussion do not develop dementia and the findings do not suggest that every person who sustains a severe TBI will develop dementia later in life.
However, the study results could lead people with TBI histories to change certain behaviors like alcohol and tobacco use, regular exercise and treating hypertension, diabetes and depression to limit other potential risk factors for dementia.
“There are some cognitive rehabilitation strategies that may decrease the cognitive deficits associated with a brain injury,” Fann said.