Long-term dementia risk is associated with both head injury and epilepsy. However, research so far has documented links between post-traumatic epilepsy (PTE) and short-term cognitive outcomes.
A new JAMA Neurology study investigated associations between dementia risk and PTE.
Study: Risk of post-traumatic epilepsy and dementia. Image credit: LightField Studios/Shutterstock.com
Record
PTE, which is characterized by unprovoked seizures for more than a week days after a traumatic brain injury, accounts for about 5% to 20% of acquired epilepsies.
Research has shown the association between PTE and short-term cognitive, functional, and psychosocial outcomes. However, understanding of long-term outcomes following a PTE diagnosis is lacking.
Epilepsy and traumatic brain injury are independently associated with long-term dementia risk. Previous research has implicated the role of neurodegenerative mechanisms in the pathophysiology of PTE.
In light of this evidence, it is possible that people with PTE will have worse long-term cognitive outcomes than those with epilepsy or head injury alone.
About the study
For this study, data were collected from the Atherosclerosis Risk in Communities (ARIC) study, which is community-based and has been collected over 30 years.
The risk of dementia associated with PTE was compared with the risk of dementia in three other groups, ie, head injury only, no head injury or seizure/epilepsy, and seizures/epilepsy only.
The hypothesis was that there was a greater association between PTE and dementia compared with either head injury or seizures/epilepsy alone.
Recognizing that dementia risk may be heterogeneous across populations and the nature of head injury, the present study examined associations of PTE with dementia risk by race, sex, age, and head injury severity and frequency subgroups.
Study findings
In this study, people with PTE appeared to have about a 4.5-fold increase in the risk of dementia compared to those without epilepsy and head injury.
There was an approximately threefold increase in the risk of dementia associated with PTE after controlling for the competing risks of stroke and mortality. The risk of dementia associated with PTE was significantly higher than for seizures/epilepsy or head injury alone. Therefore, in addition to preventing head injuries, PTE after head injury must also be prevented.
The current study adds to the existing literature by demonstrating strong associations between PTE and long-term dementia risk.
Another important feature of this study is that it examines a large sample of community-dwelling individuals followed for up to 30 years. The average age of the participants was 54 years, which is also informative in the context that the highest incidence of epilepsy and head injury occurs among older people.
In younger subjects, the relative risk of PTE-related dementia was higher compared to older subjects.
One explanation for this observation could be that older people with PTE were more likely to die before being diagnosed with dementia. This pattern appeared to persist after the competing risks of stroke and mortality were taken into account.
There was no evidence of a race or gender interaction in the analyses. Both PTE and head injury appeared to be more common among men in younger populations.
These differences were not present among older subjects. In the study cohort, women were more likely to have a head injury.
Furthermore, the risk of dementia was similar between PTE cases occurring after the first and second head injury. This was also true as it occurred after mild versus moderate/severe injuries.
Limitations of the study
The study sample included older subjects with no prior head injury at study entry. Therefore, the findings documented here may not be generalizable to those who sustain head injury early in life.
Factors such as physical function and frailty were not taken into account, which could have confounded the observed associations.
The concept of head injuries associated with loss of consciousness or requiring medical attention may not capture mild injuries.
Data on key variables such as clinical characteristics, mechanisms of injury, or acute imaging findings were also unavailable. A measure of self-reported seizure was not available at study entry, leading to the definition of seizure/epilepsy and PTE based on ICD-9/10 codes.
conclusions
In summary, this study found a higher risk of dementia among people with PTE, and this was significantly higher than the risk of dementia among people with a history of seizures or head injury alone.
These findings suggest that PTE is associated with long-term outcomes and support head injury prevention through public health measures.
More research should be conducted to reveal the risk factors and underlying mechanisms in the development of PTE. This will help focus efforts to prevent PTE after head injury.
