Increased risk of sudden unexpected death in epilepsy in females using lamotrigine: a nested, case-control study

To estimate the incidence of sudden unexpected death in epilepsy (SUDEP) in Rogaland County, Norway, in the period August 1 1995-July 31 2005, and to investigate whether use of lamotrigine (LTG) was associated with increased risk in female patients or other subgroups.

SUDEP victims were identified from autopsy reports and data from the Norwegian Cause of Death Registry. In all cases where SUDEP was considered as a possible cause of death, the hospital records were also reviewed. For each deceased, at least three living patients with epilepsy were randomly selected as controls. The market share in defined daily doses was collected for each year to estimate the number of patient-years at risk on each antiepileptic drug.

We identified 26 cases of SUDEP: 16 definite, 3 probable, and 7 possible; 15 patients were female and 11 were male. Of these, 10 patients (38.5%) were treated with LTG: 9 of these patients were female. The incidence of SUDEP was estimated as 1.0 per 1,000 patient-years when all cases were included, and 0.7 per 1,000 patient-years for definite and probable SUDEP. Seven of 12 (58.3%) of female patients with definite and probable SUDEP and 10 of 41 (24.4%) of controls matched on age and gender were on LTG (p = 0.038). The incidence of definite and probable SUDEP in women on LTG, was estimated as 2.5 per 1,000 patient-years and 0.5 per 1,000 patient-years in female who were not taking LTG (p = 0.007).

The incidence of SUDEP was significantly higher among female patients with epilepsy who were being treated with LTG than among female patients with epilepsy who were not taking LTG, and a significantly higher proportion of female SUDEP cases than controls were taking LTG. Our findings may have implications for treatment of epilepsy in female patients.