The Brain Trapped in a Vicious Cycle: Trauma, Stroke, Epilepsy, and Dementia Feed Each Other Off

A head injury can accelerate diseases like dementia and stroke, but surprisingly, these diseases can also increase the risk of suffering the trauma. A study of over 55,000 elderly people revealed a dangerous relationship that works both ways and could change how we approach prevention in old age.

Traumatic brain injury, popularly known as head trauma, is one of the leading causes of disability and loss of quality of life in the elderly. Falls, domestic accidents, and other events that cause impacts to the head can cause anything from mild injuries to severe brain damage.

In recent years, several studies have shown that people who suffer head trauma have a higher risk of developing neurological diseases such as dementia, stroke, epilepsy, and Parkinson's disease. However, an important question remained unanswered: do these diseases also increase the risk of suffering head trauma? A new study suggests that the answer is yes.

To investigate this question, researchers analyzed medical records of more than 55,000 American veterans aged 55 or older. Among them, approximately 13,800 had suffered a confirmed traumatic brain injury. To ensure that the cases truly corresponded to an acute head injury, the researchers used a combination of medical information, including recorded diagnoses, emergency room visits, and brain imaging exams such as CT scans or MRIs.

Next, each participant with a traumatic brain injury was compared to three people similar in age, sex, race, and follow-up period, but who had not suffered this type of injury.

The scientists then went back in time and analyzed the medical records to see how many people had already been diagnosed with stroke, dementia, epilepsy, or Parkinson's disease before the occurrence of the traumatic brain injury.

After that, they followed the patients for another year to find out how many would develop these same diseases after the injury. In this way, it was possible to observe whether the risk existed before the trauma, after it, or in both situations.

The results revealed something surprising. Even before suffering a traumatic brain injury, patients already presented much higher rates of these neurological diseases compared to the group without trauma. The risk of stroke, dementia, and Parkinson's disease was approximately three times higher, while the risk of epilepsy was more than four times higher.

This suggests that these conditions can make people more vulnerable to falls, accidents, and other events capable of causing head injuries. Alterations in balance, memory, attention, movement, and even environmental perception can significantly increase this risk.

But the story doesn't end there. After the traumatic brain injury, the scenario became even more worrying. During the year following the injury, patients showed a further increase in the risk of developing several of these diseases. Cases of stroke almost doubled, as did those of epilepsy.

The number of new dementia diagnoses also increased significantly. Only Parkinson's disease did not show a relevant increase after the trauma. These findings suggest that brain injury can trigger inflammatory processes, neuronal damage, and alterations in cerebral blood circulation that favor the onset or progression of neurological diseases.

The authors conclude that there is a bidirectional relationship between head trauma and neurological diseases common in old age. In other words, conditions such as dementia, epilepsy, stroke, and Parkinson's disease can increase the risk of head injury, while the injury itself can accelerate or promote the development of these diseases.

Although the study was conducted on veterans and the results need to be confirmed in other populations, the data reinforce the importance of fall and accident prevention strategies in people with neurological diseases. Protecting the brain may be one of the most effective ways to interrupt this seemingly self-perpetuating cycle.

READ MORE:

Neurologic Diagnoses Before and After Traumatic Brain InjuryA Retrospective Cohort Study of Older Veterans

Carrie Peltz, Jennifer Albrecht, Amber L. Bahorik, Feng Xia, Raquel C. Gardner, and Kristine Yaffe 

Neurology. July 28, 2026 issue 107 (2) e218214

https://doi.org/10.1212/WNL.0000000000218214

Abstract: 

Traumatic brain injury (TBI) during mid-to-late life is associated with increased risk of stroke, Parkinson disease (PD), epilepsy, and dementia. These conditions may also predispose to TBI. Thus, we investigated the incidence of dementia, stroke, epilepsy, and PD in older Veterans before and after acute TBI to determine whether there is a bidirectional association. In this retrospective cohort study, we identified Veterans aged ≥55 years who received care at US Veterans Health Affairs (VHA) facilities between October 1, 1999, and September 30, 2021, and who had acute TBI (concurrent International Classification of Diseases (ICD) code + emergency department visit + brain imaging) using VHA databases. We matched participants 3:1 to a non-TBI cohort based on age, sex, race/ethnicity, and visit date. Incident stroke, PD, epilepsy, and dementia were determined from ICD codes one year before and after TBI in the TBI cohort and over a two-year period in the non-TBI cohort. We excluded those with prevalent conditions at least 1 year before the study period. Incidence rate ratios (IRRs) and 95% CIs were calculated by comparing the pre-TBI period with the post-TBI period and with the non-TBI cohort. We included 13,801 Veterans with acute TBI and a balanced cohort of 41,403 Veterans without TBI (average age 77.8 years, 96.5% male). Veterans with TBI had higher incidence rates of the 4 conditions before TBI compared with the non-TBI cohort: incidence of stroke (IRR = 3.2 [95% CI 2.9–3.5]), dementia (IRR = 3.1, [95% CI 2.9–3.4]), and PD (IRR = 3.0 [95% CI 2.4–3.7]) was 3 times higher, and that of epilepsy was over 4 times higher (IRR = 4.4 [95% CI 3.6–5.4]). Results were slightly attenuated but remained significant after adjusting for comorbidities and health care utilization. Veterans with TBI also had higher incidence rates 1 year after TBI compared with the pre-TBI period. Incident stroke (IRR = 1.83 [95% CI 1.65–2.04]) and epilepsy (IRR = 2.29 [95% CI 1.88–2.78]) rates were twofold higher; dementia incidence was also higher (IRR = 1.24 [95% CI 1.12–1.38]), but PD rates did not differ (IRR = 1.06 [95% CI 0.82–1.36]). We found a bidirectional association between TBI and several neurologic conditions, with higher incidence rates preceding TBI and higher rates after TBI. Generalizability to non-Veteran populations is uncertain. Future studies may determine whether TBI prevention measures for adults with stroke, dementia, PD, and epilepsy are warranted.