Investigating Sleep Disturbances and Cognitive Decline in Adults With Drug-Resistant Temporal Lobe Epilepsy

Background: Drug-resistant temporal lobe epilepsy (DR-TLE) is frequently accompanied by cognitive impairment and sleep disturbances, yet their interrelationship remains insufficiently characterized using objective sleep metrics. Disrupted slow-wave sleep, sleep fragmentation, interictal epileptiform discharges (IEDs), and obstructive sleep apnea (OSA) may mechanistically contribute to memory and executive dysfunction beyond seizure burden alone. Objective: To evaluate the association between polysomnographically measured sleep abnormalities and domain-specific cognitive impairment in adults with DR-TLE. Methods: In this cross-sectional observational study, 124 adults with confirmed DR-TLE underwent overnight polysomnography and comprehensive neuropsychological assessment. Primary exposures included slow-wave sleep (N3%), sleep efficiency, arousal index, NREM IED frequency, and OSA (AHI ≥15). Outcomes were standardized z-scores across memory, executive, processing speed, and working memory domains. Multivariable linear and logistic regression models adjusted for age, education, epilepsy duration, seizure frequency, depressive symptoms, and antiseizure medication burden. Results: Mean N3 sleep was reduced (12.6% ± 5.3), and 29.8% had moderate–severe OSA. Verbal memory (mean z −1.28) and executive function (−1.12) were most impaired. Reduced N3 independently predicted poorer verbal memory (β = 0.32, p = 0.001) and increased odds of multidomain impairment per 5% decrement (OR 1.67, 95% CI 1.21–2.31). Higher NREM IED frequency was associated with executive dysfunction (β = −0.29, p = 0.002), and OSA doubled odds of multidomain impairment (OR 2.41, 95% CI 1.08–5.39). Conclusion: Objective sleep abnormalities, particularly reduced slow-wave sleep, elevated nocturnal IEDs, and OSA, are independently associated with cognitive impairment in DR-TLE, underscoring the need for integrated sleep evaluation in comprehensive epilepsy care.