CHICAGO — Poststroke epilepsy was associated with a nearly threefold increased risk for dementia compared with having no history of stroke or epilepsy, preliminary results of new research revealed.

Dementia risk was nearly double in patients with poststroke epilepsy compared with those with only one of those conditions.

The findings highlight the need for increased surveillance and interventions to prevent epilepsy in this patient subgroup, lead investigator Andrea Schneider, MD, PhD, assistant professor of neurology, University of Pennsylvania Perelman School of Medicine, Philadelphia, told Medscape Medical News.

The results were presented on April 21 at American Academy of Neurology (AAN) 2026 Annual Meeting.

Understudied Dementia Link

Both stroke and epilepsy increase the risk for dementia, but the risk associated with poststroke epilepsy — defined as one or more unprovoked seizures occurring 7 or more days following a stroke — isn’t well understood.

“We wanted to see if having both conditions rather than just one was associated with an even higher increased risk of dementia compared to, say just having a stroke diagnosis or just having an epilepsy diagnosis,” said Schneider.

Investigators analyzed data from participants in the Atherosclerosis Risk in Communities (ARIC) study, which enrolled people aged 45-64 years in Mississippi, North Carolina, Maryland, and Minnesota between 1987-89 and followed them with regular visits until 2021-2022.

Researchers divided the cohort into four groups: those with no stroke or epilepsy (n = 12,521), stroke only (n = 1148), seizures/epilepsy only (n = 684), and poststroke epilepsy (n = 140).

The median time between stroke and poststroke epilepsy was 2 years.

Cases of all-cause dementia were determined by diagnostic codes, neuropsychological tests and death certificates, and were adjudicated by an expert panel.

Over a median follow up of 26 years, 26.1% of the overall cohort developed dementia.

After adjusting for age, sex, race, education, diabetes, hypertension, smoking status, alcohol use, and APOE epsilon 4 genotype, researchers found that those with poststroke epilepsy were nearly three times as likely to develop dementia compared with those with no history of stroke or epilepsy (adjusted hazard ratio [aHR], 2.88; 95% CI, 2.34-3.54).

Those with stroke only (aHR, 1.21; 95% CI, 1.10-1.34) and epilepsy only (aHR, 1.81; 95% CI, 1.63-2.02) also had higher dementia rates compared with those with neither diagnosis.

The median time between poststroke epilepsy and a dementia diagnosis was 4 years.

Results were similar when the population was limited to those with ischemic strokes and when researchers excluded those diagnosed with seizure/epilepsy within the first 2 years of follow-up.

“As both stroke and epilepsy are independently associated with increased risk of dementia, we were thinking that there might be an additive effect — that having both of them may make the risk substantially more, which is what we found,” Schneider said.

Exact Mechanisms Unknown

The exact mechanism driving the increased dementia risk in poststroke epilepsy is yet to be sorted out. However, it is known that vascular risk factors such as diabetes and hypertension raise the risk for stroke and possibly also of epilepsy.

To help get at the underlying mechanism, the researchers are now collecting biomarker data from the ARIC cohort.

“We’re going to try to use the biomarker data to get at whether this has anything to do with more traditional Alzheimer’s–related biomarkers,” such as amyloid plaques and tau tangles, said Schneider.

“For example, is it that having epilepsy accelerates underlying Alzheimer’s pathology, or is this all more of a vascular-type picture?” she added.

The study didn’t look at people who had a diagnosis of epilepsy first and then had stroke, which might involve two separate brain insults where the epilepsy and stroke are unrelated, Schneider noted.

“I think the question is, does the temporal ordering matter or does it just matter that you have two of these conditions?” she said, adding that the new findings raise awareness about the dementia risks faced by patients with stroke who develop epilepsy.

Highlighting Prevention

That individuals with a combination of risk factors have a higher risk for a given disease than those with only one is not unexpected, said Joseph Kamtchum Tatuene, MD, clinical research fellow, Wolfson Centre for Prevention of Stroke and Dementia, University of Oxford, Oxford, England.

“For instance, a person with hypertension who smokes will have a higher risk of stroke than a non-smoker with hypertension,” Kamtchum Tatuene, who was not involved with the study, told Medscape Medical News.

He also noted that the findings didn’t include analysis stratified by severity and control status of poststroke epilepsy — for example, frequency of seizures, type of seizures, number of antiseizure drugs, and time to seizure-free status.

While Kamtchum Tatuene agrees that individuals with poststroke epilepsy may benefit from closer monitoring for cognitive changes, he suggested that more can be done to prevent poststroke epilepsy in the first place.

“Once poststroke epilepsy has occurred, it might be too late to intervene to prevent dementia,” Kamtchum Tatuene said. “There are scores to estimate the risk of poststroke epilepsy, and there are medications to prevent seizures in people at high risk, although trials are needed to inform the practice better.”

A more aggressive approach for seizure control in people with poststroke epilepsy might be more important than mere cognitive monitoring to curb dementia risk, he added.

The ARIC Study received funding from the National Heart Lung and Blood Institute. Schneider reported receiving research grant suport from the National Institutes of Health, Department of Defense, National Institute of Neurological Disorders and Stroke and being associate editor for Methodology and Statistics for the journal Neurology. Kamtchum Tatuene reported having no relevant conflicts of interest.