Traumatic brain injury (TBI) has been believed to be linked to a number of cognitive and physical illnesses later in life, including dementia, Alzheimer’s disease, and Parkinson’s disease, but research has struggled to confirm or understand these associations.
Now, a study from Finland has provided evidence showing middle-age adults who experience TBI face a drastically increased risk of developing dementia later in life, while also calling into question whether any such link exists between brain injury and Parkinson’s disease.
According to the findings published in PLOS Medicine, the risk of developing dementia was directly tied to the severity of TBI a person experienced.
“The study showed that 3.5 percent of persons with moderate-to-severe TBI [were] diagnosed with a neurodegenerative disease [such as dementia] later in life,” said study lead author Dr. Rahul Raj, an associate professor of experimental neurosurgery at Helsinki University Hospital.
“This is substantially higher compared to age-matched peers with no history of brain injury,” he noted.
Raj explained that only 1.6 percent of those with mild TBI were diagnosed with a neurodegenerative disease, suggesting moderate-to-severe TBI patients were 90% more likely to develop dementia compared to those with mild TBI.
For the study, the researchers examined data collected from more than 40,000 Finnish adults between 18 and 65 who had been hospitalized with traumatic brain injuries. The team then followed the study participants for roughly 11 years.
Approximately 20,000 of the participants had experienced mild TBI and were hospitalized for less than a day. They also showed no evidence of brain lesions, bleeding, or blood clots in the brain.
In comparison, the more than 20,000 study participants with moderate-to-severe traumatic brain injury were hospitalized for a minimum of three days and had all experienced some form of traumatic brain lesion.
The groups were largely similar, with no significant differences in age, education, or income.
The findings showed that those with mild TBI faced a slightly increased risk of developing dementia later in life, but the risk leaped significantly for those with moderate-to-severe TBI. In particular, those with moderate or severe brain injuries between the ages of 41 and 50 were at the greatest risk of developing dementia. This group was almost three times more likely to experience dementia later in life.
“It seems that the risk for developing dementia after TBI is the highest among middle-aged men. The more severe the TBI, the higher the risk for subsequent dementia. While previous studies have identified good education and high socioeconomic status as protective factors against dementia, we did not discover a similar effect among TBI survivors,” explained Raj.
“Even after [a] seemingly [full] recovery there is an underlying elevated risk for dementia that probably won’t ever go away,” the team concluded. “Thus, until we have a specific treatment for this, it is extremely important to minimize other risk factors for dementia, such as high blood pressure, high levels of cholesterol, diabetes, tobacco smoking and alcohol consumption.”