Highlights
1. Optimal sleep duration (6-8 hours) enhances executive function in focal epilepsy, stroke, and healthy groups, with the greatest benefit in epilepsy (interaction p=0.009).
2. Nonoptimal sleep predicts worse cognition up to 8 years before focal epilepsy diagnosis.
3. Focal epilepsy with poor sleep confers a 5-fold higher dementia risk (HR 5.15) vs. healthy controls—exceeding stroke-associated risk (HR 3.48).
4. Sleep optimization may offer targeted neuroprotection in epilepsy, with greater dementia risk reduction than in stroke.
Background
Focal epilepsy affects 1.2% of adults globally, with sleep disturbances and cognitive decline as disabling comorbidities. Prior studies link poor sleep to hippocampal atrophy and amyloid deposition, but epilepsy-specific mechanisms remain unclear. This study uniquely compares sleep-cognition-dementia relationships across epilepsy, stroke, and healthy cohorts.
Study Design
Cohort and Measures
The prospective UK Biobank analysis included 482,207 participants (38-72 years; 53.8% female) without baseline dementia. Groups comprised focal epilepsy (n=3,812), stroke (n=10,227), and healthy controls (n=468,168). Sleep metrics included self-reported duration, apnea, insomnia, and daytime napping. Primary outcomes were dementia incidence (Cox models) and executive function/neuroimaging metrics (generalized linear models).
Statistical Approach
Analyses adjusted for age, sex, education, and vascular risk factors. Interaction terms tested group-specific sleep effects. A nested imaging subset (n=42,345) evaluated hippocampal and gray matter volumes.
Key Findings
Cognitive Performance
Optimal sleep duration (6-8h) was associated with:
- Better executive function across all groups (beta=0.12, p<0.001)
- Stronger effects in epilepsy vs. controls (interaction beta=0.21, p=0.009)
- No significant advantage in stroke (p=0.574)
Dementia Risk
Nonoptimal sleep with focal epilepsy showed:
- 5.15x higher dementia risk vs. healthy controls with optimal sleep (95% CI 3.77-7.04)
- Greater hazard than stroke with poor sleep (HR 3.48, CI 2.82-4.26)
- Significant risk reduction from sleep optimization in epilepsy (interaction p=0.017)
Neuroimaging Correlates
Epilepsy patients with poor sleep had smaller hippocampal volumes (-0.32 SD, p=0.004) vs. controls, suggesting structural mediation of cognitive effects.
Expert Commentary
“These findings highlight sleep as a modifiable dementia risk factor in epilepsy,” notes Dr. Manohar, co-author. “The exaggerated benefit of sleep optimization in epilepsy versus stroke may reflect unique seizure-related sleep architecture disruptions or shared neurodegenerative pathways.” Study limitations include self-reported sleep data and observational design precluding causal inference.
Conclusion
Sleep duration modification may disproportionately benefit cognitive outcomes in focal epilepsy compared to other neurological conditions. Clinicians should prioritize sleep assessments in epilepsy management and consider trials of sleep interventions for neuroprotection.
Funding
UK Biobank (application 56789). No industry funding reported.
References
Tai XY, et al. Neurology. 2026;106(10):e214985. PMID: 42018962.