title: Mortality and SUDEP in epilepsy patients treated with vagus nerve stimulation.
abstract: OBJECTIVE
  The risk of premature death is increased in patients with intractable epilepsy. The effect of vagus nerve stimulation (VNS) on mortality remains unclear. In a previous study by Annegers et al., mortality was raised, comparable to similar intractable cohorts. Our aim was to calculate standardized mortality ratios (SMRs), identify epilepsy-related deaths, and estimate sudden unexpected death in epilepsy (SUDEP) rates in patients treated with VNS for epilepsy.
  
  
  METHODS
  All United Kingdom patients undergoing VNS between January 1, 1995 and December 31, 2010 at King's College Hospital, London were flagged through the national Medical Research Information Service. Analysis was performed in relation to all deaths occurring by December 31, 2010. Deceased patients were identified from the national death register, and additional information on cause and circumstances of death sought where appropriate to allow for classification of deaths.
  
  
  RESULTS
  The cohort consisted of 466 patients, with 2993.83 person-years of follow-up and a median observation period of 5.9 years. Twenty-nine deaths occurred, 27 with the device active. SMR was 7.1 (95% confidence interval [CI] 4.8-10.3) for the active device; 12 deaths were considered epilepsy related, including 10 definite or probable SUDEP and one fatal near SUDEP. Definite/probable and fatal near SUDEP occurred at a rate of 3.7/1,000 person-years. SMRs decreased from 10.5 (5.6-19.5) in the first 2 years after implantation to 5.9 (3.7-9.5) thereafter, although CIs overlapped. SUDEP rates did not alter over time.
  
  
  CONCLUSIONS
  SMRs and SUDEP rate in this study are comparable to other cohorts with intractable epilepsy, with SUDEP an important cause of death. VNS does not appear to lower the risk of premature death overall. There was a clear trend with lower SMR after 2 years of implantation, although CIs overlapped. SUDEP rates, however, did not change.
authors.affiliation: Christian Doppler Klinik, Department for Neurology, Paracelsus Medical University, Salzburg, Austria; Department for Neurology, Medical University Innsbruck, Innsbruck, Austria; Department of clinical neurosciences, Institute of Psychiatry Kings College London, London, United Kingdom.
authors.forename: Claudia A
authors.initials: CA
authors.lastname: Granbichler
authors.forename: Lina
authors.initials: L
authors.lastname: Nashef
authors.forename: Richard
authors.initials: R
authors.lastname: Selway
authors.forename: Charles E
authors.initials: CE
authors.lastname: Polkey
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002423:Cause of Death; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003645:Death, Sudden / Q000209:etiology*; D004827:Epilepsy / Q000401:mortality* / Q000628:therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D012306:Risk; D012307:Risk Factors; D055536:Vagus Nerve Stimulation / Q000009:adverse effects; D055815:Young Adult
keywords: Mortality; Refractory epilepsy; Standardized mortality ratio; Sudden unexpected death in epilepsy patients; Vagus nerve stimulation