PHILADELPHIA—The risk of sudden, unexpected death in epilepsy (SUDEP) is greater for patients with childhood-onset epilepsy that is chronic and persists into adulthood, compared with patients whose epilepsy remits, according to an overview presented at the 69th Annual Meeting of the American Epilepsy Society.
Thus, the best way to reduce SUDEP risk may be to “stop epilepsy in children before they grow up to be adults with epilepsy,” said Peter Camfield, MD, Professor Emeritus in the Department of Pediatrics at Dalhousie University in Halifax, Canada.
The reasons for differences in rates of SUDEP are unknown. One possible explanation is that SUDEP may be related to repeated seizures over time. Parents also might ensure that children adhere to their medications and provide nighttime supervision, or children may be better able survive whatever causes SUDEP for other reasons, thus leading to lower rates of SUDEP in children, Dr. Camfield said.
SUDEP “can occur at any age, but is strongly related to long-standing, chronic epilepsy,” said Dr. Camfield. “SUDEP is uncommon in childhood, but if epilepsy persists into adulthood, the rate of SUDEP may rise.”
The Effect of Age of Onset
In a study published in 2014, Thurman et al performed a systematic review of all cases of SUDEP in the literature. The investigators looked at the ages of patients with SUDEP and found that 87% of patients who died from SUDEP were older than 20.
The researchers also estimated the cumulative risk of SUDEP over time, assuming three different ages of epilepsy onset (ie, ages 1, 15, and 30) with no remission. In each scenario, the risk of SUDEP was less than 1% initially and increased over time. If epilepsy began at age 1, the risk of SUDEP did not increase much until about age 20 or 30, Dr. Camfield said. “By the time you’re 70, you would have an 8% chance of dying from SUDEP,” he said. If epilepsy began at age 15, patients had a 7.2% chance of dying of SUDEP at age 70. If epilepsy began at age 30, patients had a 4.6% chance of dying of SUDEP at age 70.
Additional data suggest that longer duration of epilepsy increases SUDEP risk. Berg et al assessed the risk of SUDEP using four prospective population-based cohorts. The investigators followed 2,239 children until about age 20. There were 10 definite or probable cases of SUDEP, resulting in a SUDEP risk of 0.33 per 1,000 person-years overall, and 0.09 per 1,000 person-years among those with uncomplicated epilepsy. “The important point for this discussion is [that] the median interval between epilepsy onset and SUDEP was 9.2 years. It didn’t happen early. It did in a few [patients], as early as five months, but usually it’s quite a few years after epilepsy develops.”
Risk of SUDEP Increases With Disease Duration
Walczak et al also studied the relationship between duration of epilepsy and risk of SUDEP. They conducted a multicenter study that included 4,578 patients from epilepsy monitoring units and 16,463 patient-years of follow-up. About half of the patients were younger than 19 at study entry. Of the 20 cases of definite or probable SUDEP, none occurred in patients who were younger than 20.
Among those who had epilepsy for 15 to 30 years, the risk of SUDEP was 1.5 times greater than the risk for patients who had epilepsy for less than 15 years. If patients had epilepsy for more than 30 years, their risk of SUDEP was approximately 14 times greater, compared with those who had epilepsy for less than 15 years, Dr. Camfield said.
Finally, in a study published in 2010, Sillanpää and Shinnar assessed the risk of SUDEP in 245 children with epilepsy who were followed for a median of 40 years. Sixty patients died. Of 103 patients who had at least a five-year terminal remission off medication, approximately 3% died, whereas among 107 patients who did not have a five-year terminal remission, 48% died.
The median age at death was 25, and 18 patients died of SUDEP. The investigators concluded that the cumulative risk of sudden, unexpected death was 7% at 40 years overall. The risk was 12% in an analysis that was limited to subjects who were not in long-term remission and not receiving medication.
“Epilepsy may be a progressive disorder with increasing risk of SUDEP with many seizures,” Dr. Camfield said. “Complete control of seizures in childhood is desirable.”
—Jake Remaly