Optimal sleep duration modified both cognitive performance and dementia risk in individuals with focal epilepsy compared with stroke patients and healthy controls, suggesting that improving sleep may be an impactful intervention to improve cognition and reduce dementia risk particularly in focal epilepsy.
Key Findings
Results
Optimal sleep duration (6-8 hours) was associated with better executive function across control, focal epilepsy, and stroke groups.
Sleep duration of 6-8 hours was defined as the optimal range.
Sleep characteristics examined included sleep duration, obstructive sleep apnea, insomnia, napping, and dozing.
Executive function measures were compared using generalized linear modeling.
The full sample included 482,207 participants aged 38-72 years (mean [SD] 57.6 [8.1] years; 53.8% female) without dementia at baseline.
Results
The positive impact of optimal sleep on executive function was significantly greater in individuals with focal epilepsy compared with healthy controls.
Interaction term p = 0.009 for focal epilepsy vs. controls.
The difference in sleep's impact on executive function was not significant in the stroke group compared with controls (interaction term p = 0.574).
This suggests a disease-specific relationship between sleep and cognition in focal epilepsy.
Results
Nonoptimal sleep was associated with worse executive function up to 8 years before the diagnosis of focal epilepsy.
This temporal relationship preceded the clinical diagnosis of focal epilepsy by up to 8 years.
Baseline assessments were performed between 2006 and 2010, with follow-up until 2021.
This finding suggests that sleep disruption and cognitive changes may precede or co-occur with the early epilepsy disease process.
Results
Individuals with focal epilepsy and nonoptimal sleep had a 5-fold increased risk of developing dementia compared with healthy controls with optimal sleep.
Hazard ratio (HR) 5.15, 95% CI 3.77-7.04, p < 0.001.
Dementia risk was assessed using Cox proportional hazard modeling.
Outcomes included risk of incident all-cause dementia and Alzheimer disease.
This dementia risk was greater than that seen in stroke individuals with poor sleep (HR 3.48, 95% CI 2.82-4.26, p < 0.001).
Results
Optimal sleep significantly modified dementia risk in individuals with focal epilepsy compared with healthy controls, with a greater improvement than seen in controls.
Interaction term p = 0.017 for focal epilepsy vs. controls regarding sleep's modification of dementia risk.
No significant difference in sleep's modification of dementia risk was seen in the stroke group compared with controls (interaction term p = 0.991).
This indicates that the protective effect of optimal sleep on dementia risk is disproportionately larger in focal epilepsy.
Methods
The study used a prospective UK Biobank cohort with a large sample and a nested imaging subsample.
Total sample: 482,207 participants without dementia at baseline.
Nested imaging subsample: 42,345 participants.
Brain imaging outcomes included total hippocampal and gray matter volumes.
Study groups were mutually exclusive participants with focal epilepsy, stroke, and healthy controls.
Sleep data were self-reported, which the authors acknowledge as a limitation.
What This Means
This research suggests that sleep quality and duration play a particularly important role in brain health for people living with focal epilepsy. Using data from over 480,000 participants in the UK Biobank study tracked for up to 15 years, researchers found that getting an optimal amount of sleep (6-8 hours) was linked to better thinking and memory skills in people with epilepsy, and that this benefit was significantly stronger for people with epilepsy than for healthy individuals or those who had experienced a stroke. Notably, poor sleep was associated with worse cognitive performance even up to 8 years before an epilepsy diagnosis was made, hinting that sleep problems may be an early marker of the disease process.
The study also found that people with focal epilepsy who slept poorly had roughly five times the risk of developing dementia compared to healthy people who slept well — a higher risk than even stroke patients with poor sleep, who had about 3.5 times the risk. Importantly, achieving optimal sleep appeared to reduce dementia risk more meaningfully in people with epilepsy than in the general population or in stroke patients, suggesting that sleep may be a particularly powerful factor in this group.
This research suggests that sleep could be a meaningful target for protecting brain health in people with focal epilepsy, potentially more so than in other neurological conditions. The findings highlight the importance of monitoring and addressing sleep problems in epilepsy care, though the researchers note that their sleep data were based on self-reports, which is a limitation. Future research could explore whether treating sleep disorders in people with epilepsy actively reduces cognitive decline or dementia risk.
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Tai X, Zhao S, Liem B, Galovic M, Husain M, Sen A, et al.. (2026). The Relationship Between Sleep, Cognition, and Dementia Risk in People With Focal Epilepsy.. Neurology. https://doi.org/10.1212/WNL.0000000000214985