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Number, severity of brain injuries raises dementia risk, study says

SEATTLE (AP) — A large study is adding to evidence of a link between traumatic brain injuries and dementia later in life.

Repeated injuries and severe ones posed the greatest danger in the study involving 2.8 million people in Denmark. The research was published Tuesday in the journal Lancet Psychiatry.

Overall, the risk was small. About 95 percent of people with a brain injury never developed dementia.

But a single severe brain injury increased the risk of later dementia by 35 percent compared with a person who never had a brain injury. A mild brain injury increased the risk by 17 percent.

Lead researcher Dr. Jesse Fann of University of Washington School of Medicine in Seattle says the findings show that each additional brain injury adds to the danger.

“What surprised us was that even a single mild TBI was associated with a significantly higher risk of dementia,” said Fann, a professor of psychiatry and behavioral sciences at the University of Washington School of Medicine. "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."

Dementia affects 47 million people worldwide, a number expected to double in the next 20 years, the study said.  Every year, more than 50 million people worldwide experience a TBI, which occurs when an external force disrupts the brain's normal function. Leading causes include falls, motor vehicle accidents, and assaults.

Fann said it's important to recognize that most people who sustain a single concussion do not develop dementia. And he clarified that the findings do not suggest that every person who sustains a severe TBI will develop dementia later in life. 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.