People with epilepsy may face a significantly higher risk of developing dementia before the age of 65, according to a large new study that analyzed health records from hundreds of thousands of people in France and Sweden.
Researchers found that epilepsy appeared repeatedly among people later diagnosed with young-onset dementia, a form of the condition that develops before age 65. The study, published in Neurology, the medical journal of the American Academy of Neurology, used two separate research approaches across two countries and arrived at similar results.
Dr. Rebecca Spiegel, a neurologist and chief of EEG and epilepsy at Stony Brook Medicine, spoke to Newsweek about the recent findings.
"They are important, but we need to be cautious," she said. "In some patients, new-onset seizures may be an early manifestation of neurodegeneration rather than its cause, and, in addition, people with epilepsy may experience cognitive difficulties that do not necessarily indicate dementia and may be treatable, particularly given the disproportionately high incidence of depression and anxiety in this population."
Link Between Epilepsy and Young-Onset Dementia
The researchers stressed that the findings do not show that epilepsy directly causes young-onset dementia. Instead, the study identified a strong association between the two conditions. They also noted that although the relative increase in risk was substantial, the overall likelihood of developing young-onset dementia remained low.
Young-onset dementia is less common than dementia diagnosed later in life, but it can have a particularly profound and devastating impact because it affects people during their working years and often while they are caring for families.
To investigate possible links with epilepsy, researchers used national health databases in France and Sweden.
One part of the study looked backward in time to determine whether people diagnosed with young-onset dementia had previously received an epilepsy diagnosis or epilepsy medication. A second analysis followed people with epilepsy over time to see whether they later developed dementia.
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In the retrospective analysis, researchers compared 11,360 people with young-onset dementia in France with 113,600 people of the same age and sex who did not have dementia. In Sweden, they compared 16,433 people with young-onset dementia with 164,330 people without the condition.
The differences between the groups were striking.
In France, 12.5 percent of people with young-onset dementia had previously been diagnosed with epilepsy, compared with just 1.2 percent of those without dementia. Researchers also found that 27.3 percent of people with dementia had received epilepsy medications, compared with 10.3 percent of those who did not have dementia.
The Swedish data showed similar patterns, strengthening the consistency of the findings across two separate national health systems.
Following People Over Time
The second part of the research tracked French adults aged 30 to 55 who were newly diagnosed with epilepsy in 2008 and followed them for up to 10 years.
Over the follow-up period, 2.2 percent of newly diagnosed patients developed young-onset dementia. That compared with 1.7 percent of people who already had epilepsy before 2008 and 0.2 percent of people without epilepsy.
After accounting for other factors that can affect dementia risk, including stroke, mood disorders and traumatic brain injury, researchers found that people newly diagnosed with epilepsy were six times more likely to develop young-onset dementia than people without epilepsy. Those with existing epilepsy were 74 percent more likely to develop dementia than people who did not have the condition.
Still, the study authors cautioned that several limitations remain. The databases did not contain detailed information about the specific types or causes of dementia, nor about the different forms of epilepsy experienced by participants.
The researchers also noted that the study relied on health data from France and Sweden, two high-income countries with universal health care systems. As a result, the findings may not apply equally to populations in other countries or health care settings.
While the study adds to growing evidence of a connection between epilepsy and cognitive decline, further research is needed to determine why the relationship exists and whether reducing epilepsy-related risks could help lower the likelihood of young-onset dementia.
"The reassuring message is that, despite the increased relative risk, the vast majority of patients with epilepsy in this study did not develop young-onset dementia," Spiegel said. "Nevertheless, the findings should encourage greater attention to cognitive assessment in people with epilepsy."
Newsweek contacted the study's press contact at the American Academy of Neurology, of which Neurology is a medical journal, for more information.
Reference
Calonge, Q., et al. (2026). Association Between Epilepsy and Young-Onset Dementia. Neurology. https://doi.org/10.1212/WNL.0000000000218700.
Contact Newsweek editors on this story: Kara Dolman and Paul Donnelley.