Nature Medicine | Spoonful of Medicine

Scaled-up study of soldiers points to doubled risk of dementia from head injury


PARIS — A massive review of the medical records of nearly 300,000 US veterans lends weight to the notion that traumatic brain injury might contribute to the risk of cognitive impairment later in life. Neurologist Kristine Yaffe of the University of California–San Francisco and her colleagues reviewed seven years’ worth of data from the files of the former military troops, and found that these types of head injuries were linked to a doubled risk of dementia.

Yaffe, who presented the findings here today at the Alzheimer’s Association International Conference, says that it’s the largest analysis of its kind to date. All of the 281,540 veterans included in the analysis were aged 55 years or older and free of dementia at check-up visits before 2001. However, during seven years of follow up, 2% of the older veterans had a diagnosis of traumatic brain injury (TBI). Of those with TBI, 15.3% developed dementia, as opposed to 6.8% of those who were free of this type of head injury. After adjusting for other possible contributing factors, such as post-traumatic stress disorder — which previous research has hinted might contribute to impaired cognitive function — the scientists calculated that TBI is linked to a 2.3-fold increased risk of dementia.

Based on the limitations of the medical records, Yaffe and her colleagues were unable to determine the severity and extent of the head injuries among the veterans who had a TBI diagnosis. “We couldn’t delve down and say whether it was repetitive or not,” she explains. She adds that while her team was able determine the type of TBI the veterans sustained, ranging from skull fractures to concussions, the dementia risk did not seem to vary much between the kinds of head injury.

Previous studies have linked TBI with brain inflammation, a hallmark of diseases such as Alzheimer’s. As a result, scientists speculate that the head trauma suffered in combat might set off a cascade of physiological events in the brain that ultimately precipitates dementia. TBI is not uncommon in the wars in Iraq and Afghanistan; in 2009 officials from the US Department of Defense estimated that 360,000 US soldiers in these conflicts had suffered head injuries. “There aren’t a lot of treatments for acute brain injury,” Yaffe notes.

Some doctors have tried giving Alzheimer’s drugs, such as Aricept (donepezil), to treat symptoms of memory loss in patients with TBI. But Yaffe stresses that the use of these drugs for warding off memory decline and dementia in head injury victims remains unclear. “I think it’s still experimental,” she says.

Image of by DVIDSHUB via Flickr.


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