Sudden unexpected death in epilepsy: a review of incidence and risk factors.

Sudden unexpected death in epilepsy (SUDEP) is the most important direct epilepsy-related cause of death. However, SUDEP is rare in patients with new onset epilepsy and in patients in remission. Incidence is about 0.35 cases/1,000 person-years in population-based incidence cohort of epilepsy. Incidence is considerably higher in patients with chronic epilepsy, 1-2/1,000 person-years, and highest with severe, refractory seizures, 3-9/1,000. The highest rates occur from 20 to 40 years. Most SUDEP appears seizure-related. When witnessed, the fatal event generally occurred in association with generalized tonic-clonic seizure. Two recent case-control studies suggest that seizure frequency is the strongest risk factor for SUDEP: relative risk = 23 (95% CI = 3.2-170) for persons with > or =1 seizure during the year of observation versus seizure-free patients. Onset of epilepsy at an early age and long duration of the disorder are other risk factors. Although SUDEP has not been associated with the use of any particular antiepileptic drugs (AEDs), some case-control studies have pointed to an association between SUDEP and polytherapy with AEDs and frequent dose changes independent of seizure frequency. Although recent epidemiological studies have been helpful in identifying patients at risk for SUDEP, providing clues to mechanisms behind SUDEP, no single risk factor is common to all SUDEP, suggesting multiple mechanisms or trigger factors. Seizure control seems of paramount importance to prevent SUDEP. Further large-scale case-control studies are needed to assess the role of AEDs in order to form a basis for treatment strategies aiming at seizure control and prevention of SUDEP.