People with epilepsy may die unexpectedly without a clear structural or 
pathologic cause. This condition is called sudden unexpected death in epilepsy 
(SUDEP), and it accounts for a large proportion of deaths among people with 
epilepsy. SUDEP incidence rates vary with the cohort studied, ranging from 0.35 
per 1,000 person-years of follow-up in population-based studies to 9.3 per 1,000 
person-years in patients with refractory epilepsy. Although many studies have 
been performed, the causes of SUDEP are not understood. However, even without 
precise knowledge of the underlying pathogenic mechanism(s), SUDEP prevention 
could start with the identification of the most prominent risk factors. SUDEP 
seems to occur more commonly during sleep and it preferentially affects young 
adults with medically intractable epilepsy (especially tonic-clonic seizures), 
individuals who also have neurologic comorbidity, and patients receiving 
antiepileptic drug polytherapy. This article reviews the clinical features 
associated with SUDEP and suggests preventive measures for this condition.