A single traumatic brain injury in early years could be an indicator of dementia later in life, suggests a new study published in the journal Lancet Psychiatry. "Individuals with a history of traumatic brain injury, including those with less severe injuries, have an increased risk of developing dementia, even decades after," said Jesse Fann of the University of Washington, lead author of the study.
An estimated 50 million people a year suffer a traumatic brain injury (TBI) and about 50 percent of all people worldwide have one at some time in their lives, according to the study. Dementia afflicts 47 million people, and that number is expected to double by 2038.
The new study is unusually large — relying on 2.8 million patients in Denmark — and long, tracking them over 36 years. Its findings roughly align with a 2018 study of 3.3 million patients in Sweden.
Fann found that a brain injury in one’s 20s was associated with a 60 percent dementia risk increase in one’s 50s. In general, dementia risk for the 2.8 million Danes was 24 percent higher for those with TBI, 35 percent if the TBI was severe, and 17 percent if mild. “What surprised us was that even a single mild TBI was associated with a significantly higher risk of dementia,” said Fann. The risk increase was 33 percent for those with two to three TBIs, 61 percent for four TBIs, and 183 percent for five or more. Male TBI patients had a 30 percent increased risk overall, and females 19 percent. The mean age at first dementia diagnosis was 80.7 years.
Statistical association does not prove causation, and Fann stressed that 95 percent of the brain-injured patients did not develop dementia at all. There is also a considerable risk when TBI patients and health providers give up hope — which is not an evidence-based conclusion.
“Expectations of unfavorable outcomes in the elderly can lead to treatments being withheld or prematurely withdrawn,” said The Lancet Neurology Commission on TBI in a 2017 statement, “with resulting poorer outcomes reinforcing therapeutic nihilism in the management of these patients. However, with appropriate care good results can be obtained.”
Fann suggests that TBI patients consider improving their odds of avoiding dementia by reducing alcohol and tobacco use, exercising, and seeking treatment for hypertension, obesity, diabetes and depression.