Epilepsy increased the risk for sudden cardiac death threefold in a case-control study involving 1,019 cases of sudden cardiac death.

“A substantial portion of deaths in epilepsy happen suddenly,” said Dr. Abdennasser Bardai of the University of Amsterdam and his colleagues. Both epilepsy and sudden cardiac arrest (SCA) are caused by pathological electrical activity, but the risk for SCA in epilepsy patients has not been well studied, they noted.

The researchers reviewed data from the Amsterdam Resuscitation Studies (ARREST) conducted between July 2005 and January 2010. They matched 1,019 cases of SCA with 2,834 controls. The average age of the patients was 64 years for cases and 58 years for controls, and the study population was about 70% male (PLoS ONE 7:e4274 [doi:10.1371/journal.pone.0042749]).

Overall, 12 SCA cases (1.4%) and 12 controls (0.4%) had an active epilepsy diagnosis. Individuals with epilepsy had nearly three times greater odds for having SCA than did controls (odds ratio, 2.9) after adjustment for cardiac ischemia, diabetes, and heart failure.

In a subanalysis, SCA risk was increased in individuals with epilepsy younger than 50 years, compared with those aged 50 years and older, and in women compared with men. Established risk factors for SCA, including hypertension, diabetes mellitus, heart failure, and hypercholesterolemia, also were risk factors in this study, the researchers noted.

Sudden unexpected death in epilepsy (SUDEP) “most frequently occurs in people with chronic epilepsy, poor seizure control, antiepileptic drug polytherapy, young age of onset, and a long history of epilepsy,” the researchers wrote. “Our findings may suggest that the risk for SCA from cardiac causes extends to people with epilepsy beyond those with SUDEP,” they added.

Although the findings suggest that SCA may contribute to SUDEP, other causes, such as respiratory depression, cannot be ruled out, the researchers said. In 11 of the 12 cases of SCA in epilepsy patients, no sign of seizure activity was noted before the SCA. The study was limited by the small number of individuals with active epilepsy who had SCA, and more research is needed to determine the causes of SCA risk in patients with epilepsy, the researchers added.

But the findings are “the first systematically collected evidence from a community-based study that epilepsy in the general population is associated with an increased risk for SCA,” they wrote.

Dr. Bardai had no financial conflicts to disclose.