Brain Disorders and TBI May Fuel Each Other

The connection between traumatic brain injury (TBI) and neurologic disorders may run both ways, a large retrospective study of U.S. military veterans suggested.

Older adults with TBI were more likely than those without TBI to have received a previous diagnosis of epilepsy (incidence rate ratio [IRR] 4.4), stroke (IRR 3.2), dementia (IRR 3.1), or Parkinson’s disease (IRR 3.0), reported Carrie Peltz, PhD, of the San Francisco Veterans Affairs Health Care System, and colleagues in Neurology.

The relationship also extended in the opposite direction. Compared with a 1-year period before injury, older adults had elevated risks of developing epilepsy (IRR 2.29), stroke (IRR 1.83), and dementia (IRR 1.24) 1 year after TBI. Rates of Parkinson’s were similar before and after TBI.

“Our findings raise the possibility that dementia, stroke, epilepsy, and Parkinson’s disease are themselves risk factors for TBI in older people,” Peltz said in a statement. These neurologic disorders impair motor control, balance, gait, and cognition, making people more likely to fall, she pointed out. Falls are a leading mechanism for TBI in older age groups.

“Our results argue for screening older adults for their risk of falling at the time they are diagnosed and quickly referring them to physical therapy, occupational therapy, or fall prevention programs,” Peltz observed. “Strength and balance training, making changes at home such as adding grab bars and removing tripping hazards, and reviewing medications have all been shown among older adults in general to reduce the risk of falls.”

Multiple studies have found that brain injury — even mild TBI — can double the risk of dementia or raise the odds of subsequent epilepsy or stroke, the researchers noted. Few studies have looked at the relationship in reverse.

Peltz and colleagues assessed data from military veterans ages 55 and older who received care at Veterans Health Affairs facilities from October 1999 through September 2021.

The sample included 13,801 veterans with acute TBI and 41,403 veterans without TBI, matched on age, sex, race or ethnicity, and visit date. Acute TBI was defined as a new TBI diagnosis that occurred on the same day as an emergency department visit with a CT or MRI scan within 1 day.

The study population was 81% white, 12.8% Black, 3.5% Hispanic, and 1% Asian. The average age was 77.8 years and nearly all participants (96.5%) were male.

The researchers identified incident stroke, Parkinson’s disease, epilepsy, and dementia by ICD codes 1 year before and after brain injury in the TBI cohort, and over a 2-year period in the non-TBI cohort. They excluded people with prevalent conditions at least 1 year before the study period.

The study had several limitations, the researchers acknowledged. The need to have medical records 1 year after TBI ruled out veterans with severe brain injury who died within a year, they said. People with mild TBI who did not seek medical care also were not included.

All participants were military veterans and results may not apply to other populations, Peltz and co-authors noted. In addition, identifying outcomes like dementia through diagnostic codes may not capture mild or early-stage disease and some cases may be misclassified. “Future studies with richer phenotyping, prospective ascertainment, and longer follow-up will be informative,” they wrote.