Status epilepticus without an underlying cause and risk of death: a population-based study

OBJECTIVE: To determine the independent effect of status epilepticus (SE) on risk of death. DESIGN: Retrospective cohort study. The increased risk of death after SE has been largely ascribed to the underlying medical condition. It is unknown whether SE itself affects risk of death. We address this question by studying idiopathic/cryptogenic SE. SETTING: Population-based study. PARTICIPANTS: We identified all incident idiopathic/cryptogenic unprovoked seizures in the population of Rochester, Minnesota, from January 1, 1955, through December 31, 1984, and observed them until death, loss to follow-up, or the end of the study. MAIN OUTCOME MEASURES: We compared the risk of death in those with a brief unprovoked seizure (<30 minutes) with risk of death in those with an unprovoked seizure of 30 minutes or longer (SE), using Kaplan-Meier and Cox proportional hazards regression. The standardized mortality ratio was also determined. RESULTS: We ascertained 291 people with a first brief unprovoked seizure and 16 with SE. There were 27 deaths among people with seizure and 5 deaths (all aged > 65 years) among people with SE. Compared with people with seizure, the adjusted relative risk for death in those with SE was 2.4 (95% confidence interval CI], 0.9-6.3) over 10 years. It was increased 5-fold (relative risk, 5.1; 95% CI, 1.6-15.7) among those older than 65 years and 6-fold among those with SE who later developed epilepsy (relative risk, 6.3; 95% CI, 1.5-26.0). Compared with the general population, the standardized mortality ratio was 2.6 (95% CI, 0.8-5.3) for SE and 1.2 (95% CI, 0.8-1.6) for a first seizure of short duration. CONCLUSION: Idiopathic/cryptogenic SE was associated with an increased risk of death among elderly persons and those who later developed epilepsy.