Sleep state and the risk of seizure recurrence following a first unprovoked seizure in childhood.

In a prospective study, we have followed 347 children identified at the time of a first unprovoked seizure for a mean of 46 months. To date, 135 (39%) have experienced a seizure recurrence. In this study, we analyzed recurrence risk as a function of whether the child was asleep or awake at the time of the first seizure. The cumulative recurrence risks for children whose first seizure occurred in sleep was 28% at 0.5 years, 39% at 1 year, 53% at 2 years, and 55% at 4 years, compared with recurrence risks of 18%, 23%, 30%, and 35% at the same intervals in children whose first seizure occurred while awake (p < 0.001). The association of a first seizure during sleep with an increased recurrence risk was present primarily in children with idiopathic seizures. It occurred in both those with a normal and an abnormal EEG. On multivariable analysis, sleep state, etiology, and the EEG were statistically significant predictors of recurrence risk. In children who experienced a seizure recurrence, the recurrences occurred in the same sleep state in 73% of the cases (p < 0.0001). This was also true of subsequent recurrences. We conclude that the occurrence of a first seizure in sleep is associated with an increased risk of recurrence. Subsequent seizures, if they do occur, usually occur in the same sleep state as the initial seizure.