Sudden unexpected death in epilepsy: people with nocturnal seizures may be at highest risk.

Purpose: Most people with epilepsy who die suddenly and whose death is attributed to sudden unexpected death in epilepsy (SUDEP) are found in or by the bed for unknown reasons. We assessed whether those with sleep-related SUDEP were more likely to have nocturnal seizures, and whether seizure patterns (diurnal vs. nocturnal) differed from people dying suddenly and living controls with epilepsy.

Methods: Seizure patterns in a cohort of 154 people with epilepsy who died suddenly and after autopsy conformed to the definition of SUDEP and 616 controls living with epilepsy were classified as having "exclusively diurnal" or "nocturnal seizures." Comparisons were made between the groups. SUDEP was classified as sleep-related or non-sleep-related based on eyewitness accounts and the circumstances surrounding death.

Key Findings: SUDEP was primarily a sleep-related (58%) and unwitnessed (86%) event. If sleep-related, SUDEP was more likely to be unwitnessed [odds ratio (OR) 4.4, 95% confidence interval (CI) 1.6-12]. Those with sleep-related SUDEP were more likely to have a history of nocturnal seizures than those who had non-sleep-related SUDEP (OR 3.6, 95% CI 1.4-9.4). Those who died were more likely to have a history of nocturnal seizures than living controls (OR 3.9, 95% CI 2.5-6.0). After correction for previously established SUDEP risk factors (Langan et al., 2005), the presence of nocturnal seizures remained significant (OR 2.6, 95% CI 1.3-5.0).

Significance: Nocturnal seizures seem to be an independent risk factor for SUDEP. These findings underscore the importance of preventive measures, which may include night supervision.