Older adults with TBI should be monitored for signs of cognitive impairment, researchers advise.
PARIS—Older veterans with traumatic brain injury (TBI) have more than a twofold increased risk for dementia, according to research presented at the 2011 Alzheimer’s Association International Conference.
Kristine Yaffe, MD, Professor of Psychiatry, Neurology, and Epidemiology at the University of California, San Francisco and Director of the Memory Disorders Program at the San Francisco VA Medical center, and colleagues reviewed medical records of 281,540 US veterans. All participants were ages 55 or older and received care through the Veterans Health Administration, had at least one inpatient or outpatient visit from 1997 to 2000 and a follow-up between 2001 and 2007, and did not have a dementia diagnosis at the start of the study. The investigators searched the database for TBI and dementia diagnoses and investigated whether TBI of any type was associated with greater risk of dementia, while taking into account demographics and other medical conditions, including psychiatric disorders.
The risk of dementia was 15.3% in those with a TBI diagnosis, compared with 6.8% in those without a TBI diagnosis, the researchers reported. The adjusted hazard ratio for incident dementia in those with any TBI diagnosis was 2.3 for the risk of developing dementia over seven years and was significant for all TBI types. Approximately 2% of older veterans had a TBI diagnosis during the study period.
“This issue is important, because TBI is very common,” said Dr. Yaffe. “About 1.7 million people experience a TBI each year in the US, primarily due to falls and car crashes. TBI is also referred to as the ‘signature wound’ of the conflicts in Iraq and Afghanistan, where TBI accounts for 22% of casualties overall and 59% of blast-related injuries.
“The data suggest that TBI in older veterans may predispose them toward symptomatic dementia, and they raise concern about the potential long-term consequences of TBI in younger veterans,” she said.
The researchers suggest that there are several potential mechanisms by which TBI could increase dementia risk. TBI is associated with swelling of axons, which is accompanied by accumulation of proteins, including beta-amyloid.
According to the investigators, amyloid plaques similar to those found in the brains of patients with Alzheimer’s disease are present in up to 30% of TBI patients who do not survive their injuries, regardless of age. It is possible that these injuries result in the death of axons and neurons, even after a single TBI. Loss of axons and neurons could result in earlier manifestation of Alzheimer’s disease symptoms.
“Our findings raise hope that early treatment and rehabilitation following TBI may help prevent long-term consequences such as dementia,” Dr. Yaffe said. “They also suggest that older adults who experience a TBI should be monitored for signs of cognitive impairment following their injuries.”