After one of the largest ever investigations into the link between traumatic brain injury (TBI) and cognitive decline in later life, Danish and USA researchers concluded that the younger a person was when sustaining a head injury, the higher the risk of developing Alzheimer's and other forms of dementia.
The risk increases by 24 percent, the researchers write in the journal The Lancet Psychiatry, and is relative to the number and severity of brain injuries.
A traumatic brain injury occurs when an external force such as a bump or blow to the head disrupts the normal function of the brain.
'Over 95% of people who developed dementia in this study hadn't had a brain injury, so the study does not tell us that traumatic brain injury is a definite cause of dementia. But he said the findings might lead people with TBI histories to change their behaviors toward other potential risk factors for dementia, such as limiting alcohol and tobacco use, engaging in regular exercise, preventing obesity, and treating hypertension, diabetes, and depression.
The study, in Lancet Psychiatry, used Danish health databases that included all residents as of January 1, 1995, who were at least 50 years old at some time during the 36-year follow-up, from 1977 to 2013.
Researchers have come up with a new test to measure how severe a brain injury is - a step forward in improving patient care. Even compared to that group, the TBI group had higher risk for dementia. But the risk increased significantly for people with multiple brain injuries, and for people who were in their 20s at the time for their first brain injury. Five or more brain injuries, the risk is almost 3 times the risk compared to someone without a brain injury.
Fann said it's important to recognize that most people who sustain a single concussion do not develop dementia.
He also suggested people who suffer a TBI get an evaluation and seek treatment for persisting problems.
The findings are particularly worrying in light of recent attention around the risk of concussion in contact sports like boxing, rugby and football.
For the study, researchers at University of Washington tracked all diagnoses of TBI from Danish national registries from 1977 to 2013.
For years, scientists have studied the effects of traumatic brain injuries that appear in professional athletes, looking for ties to dementia later in life. "If they have a history of traumatic brain injury, they should do their best to prevent further traumatic brain injuries".