To analyze real-world mortality rates in patients with Lennox-Gastaut (LGS) or Dravet syndromes (DS) in the US.

LGS and DS are rare developmental and epileptic encephalopathies characterized by pharmacoresistant seizures and cognitive impairment. Mortality rates in LGS and DS have been reported as 15.84 and 6.12/1000 patient-years, respectively. Real-world mortality data in LGS and DS are limited.

This retrospective analysis identified patients in the US diagnosed with LGS or DS from October 01, 2015, to December 31, 2023, using Real Chemistry’s open claims database. Patients were included if they had ≥2 LGS or DS claims in the study period and were categorized as deceased if they had a date of death (DOD) after October 01, 2015 and ≤60 days from their last claim to DOD. Outcomes analyzed included annual all-cause case fatality (primary), comorbidities in patients with vs. without a mortality event, and SUDEP-related fatality rates. Standardized mortality ratios (SMRs) were reported.

In total, 29,626 patients with LGS and 2259 patients with DS were included; of those, 2509 (8.5%) and 52 (2.3%) had a mortality event, respectively. The yearly adjusted case fatality rate for LGS was 4.2%-6.2% from 2016-2023; the SUDEP-related rate was 1%-2%. LGS SMR was 5.12-6.45 from 2016-2022. Feeding difficulties and cardiovascular/respiratory complications were most significantly associated with mortality in LGS. In patients with DS, the 5-year adjusted case fatality rate was 8.6%; the SUDEP-related rate was 2.1%. DS SMR was 6.73-9.12 from 2020-2022. From 2019-2023, encephalopathy and feeding difficulties were most significantly associated with mortality in DS.

These data provide real-world estimates of LGS and DS mortality and SUDEP-related mortality rates from claims data. In both LGS and DS, feeding difficulties were associated with increased mortality rates.