Poor sleep linked to higher dementia risk in epilepsy

For people with epilepsy, getting poor sleep was associated with a higher risk of dementia compared to people without epilepsy, according to a study published April 22, 2026, in Neurology^®, the medical journal of the American Academy of Neurology. In addition, getting optimal sleep, six to eight hours a day, is associated with higher cognitive scores than getting poor sleep, less than six or more than eight hours a day. The study does not prove that poor sleep quality causes worse cognition and dementia risk, it only shows an association.

For this study, researchers looked specifically at focal epilepsy, which is when seizures start in one part of the brain.

"Sleep problems can make seizure activity worse while seizures themselves can disrupt sleep, but it remains unclear the extent to which poor sleep impacts thinking skills and the risk of dementia," said study author Xin You Tai, DPhil, of the University of Oxford in the United Kingdom. "Our study suggests getting optimal sleep may be especially beneficial to cognition and dementia risk in people with focal epilepsy."

The study involved 482,207 people with an average age of 58 who did not have dementia at the start of the study. Of participants, 3,788 had epilepsy, 6,372 had a history of stroke, and a control group of 472,047 people had neither condition. People with stroke were included as a comparison group since they had a neurological condition but not seizures. Participants were followed for an average of 12 years, during which 5,826 people developed dementia.

Participants completed questionnaires to report how long they slept.

They had cognitive tests to measure executive function, which includes planning and problem-solving skills.

Researchers found optimal sleep was associated with better executive function in all three groups. The impact of optimal sleep was stronger in people with focal epilepsy compared to the impact in people without epilepsy or stroke. Conversely, the impact of optimal sleep in people with stroke was not elevated compared to people without epilepsy or stroke.

Of people with epilepsy, 2% who had optimal sleep and 5% who had poor sleep developed dementia. Of those with stroke, 4% with optimal sleep and 6% with poor sleep developed dementia. Of people with neither condition, 1% with optimal sleep and 2% with poor sleep developed dementia.

After adjusting for factors such as age, sex, education and socioeconomic status, researchers say people with epilepsy and poor sleep had a five-fold increased risk of developing dementia, and people with stroke had a three-and-a-half-fold increased risk, when compared to people without epilepsy and stroke with optimal sleep.

"Importantly, we also found the difference in dementia risk between optimal and poor sleep was larger in people with focal epilepsy than in people in the control group," said Tai. "Conversely, for people with stroke, after adjustments, there was no difference in dementia risk between optimal and poor sleep when compared to people in the control group. Improving sleep may offer an effective and affordable management strategy to lower dementia risk in people with focal epilepsy."

A limitation of the study was that participants reported their sleep duration rather than being monitored and may not have remembered everything accurately.