Are older people with brain diseases more likely to have a TBI?

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Highlights:

• A new study suggests the links between traumatic brain injury (TBI) and certain brain diseases may go in both directions in older adults.
• In older veterans with recent TBI, a prior diagnosis of stroke, dementia or Parkinson disease was three times more likely, and epilepsy four times more likely, than in those without TBI.
• The study does not prove that the conditions cause an increased risk of TBI; it only shows an association.
• Researchers also looked the other direction to see which participants developed any of the conditions after TBI. Older veterans with TBI were twice as likely to develop stroke or epilepsy and 24% more likely to develop dementia after TBI compared to before TBI. The rate of Parkinson disease did not differ.
• The authors say the results support screening older adults with these conditions for their risk of falling to prevent TBI.

For traumatic brain injury and certain brain diseases, it looks like the risk may go in both directions, according to a study published on June 17, 2026, in Neurology^®, the medical journal of the American Academy of Neurology.

Studies have shown that having a TBI may increase the risk of developing a stroke, dementia, epilepsy, or Parkinson disease. For this new study, researchers looked at older veterans who recently had a TBI to see if they were more likely to have any of those conditions than people who did not recently have a TBI.

They found that older veterans with a recent TBI were three to four times more likely to have been diagnosed with one of the four conditions in the previous year than people of similar ages who did not have a TBI.

The study does not prove that the conditions cause an increased risk of TBI; it only shows an association.

“These findings suggest that the period after being diagnosed with a neurologic condition is an important time period for preventing TBI,” said study author Carrie Peltz, PhD, of San Francisco Veterans Affairs Health Care System in California. “Our findings raise the possibility that dementia, stroke, epilepsy, and Parkinson disease are themselves risk factors for TBI in older people. Neurologic diseases often impair motor control, balance, gait, coordination, and thinking skills—all of which make people more likely to fall, which is the main cause of TBI in older adults.”

For the study, researchers looked at 13,801 veterans with an average age of 78 who had a recent TBI and compared them to 41,403 veterans the same age who did not have a TBI. They looked at their health records for a year before and after the TBI, or at a similar timeframe for those without TBI. People who had any of the four conditions before that time point were not included in the study.

For all four conditions, people with a TBI had a higher rate of developing the condition in the prior year than people without a TBI. For stroke, the rate was 64 cases per 1,000 person-years for people with a TBI, compared to 20 cases for those without a TBI. Person-years represent both the number of people in the study and the amount of time each person spent in the study. For dementia, the rates were 58 for those with TBI compared to 19. For epilepsy, the rates were 14 for those with TBI compared to four. And for Parkinson disease, the rates were 10 and 3.

When researchers adjusted for other factors that could affect the risk of TBI, such as diabetes, smoking, and having had a heart attack, they found that people who had a TBI were four times more likely to have been recently diagnosed with epilepsy and three times more likely to have been diagnosed with stroke or Parkinson disease.

The study also looked the other direction at which participants developed any of the conditions after TBI compared to before a TBI. Researchers found that after a TBI, people were twice as likely to develop stroke or epilepsy than before a TBI. They were 24% more likely develop dementia. But the rate of Parkinson disease was not different between the two groups.

Peltz said not finding an increased risk of Parkinson disease may be due to the short follow-up time of the study, since previous studies have found an increased risk.

“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 said. “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.”

A limitation of the study is that the requirement for medical information one year after the TBI would rule out people with severe TBI, leading to death within a year. In contrast, people with mild TBI who did not seek medical care were also not included. In addition, since the participants were all veterans, the results may not apply to other populations.

The study was supported by the U.S. Department of Defense.

Source: News Release
American Academy of Neurology
June 17, 2026