Evolution over time of SUDEP incidence: A nationwide population-based cohort study.

Prompted by a recent report on declining incidence of sudden unexpected death in epilepsy (SUDEP) following implantation of a vagus nerve stimulator (VNS), we analyzed SUDEP risk over 6 years in a population-based cohort of 60 952 epilepsy patients in Sweden. All deaths from July 1, 2006 through December 31, 2011, were identified. Those with epilepsy mentioned on the death certificate were adjudicated for SUDEP using medical records and autopsy reports. In all, 292 SUDEP cases were identified. Comparing the first years (2006-2007) with the subsequent 4 years (2008-2011), the crude and standardized (to the US 2000 population) incidence of SUDEP (whether or not possible SUDEP was included) was significantly lower during the second time period; Incidence rate ratios based on standardized rates was estimated at 0.76 (95% confidence interval [CI] 0.60-0.97, P = .027) for SUDEP. The incidence of SUDEP decreased by 7% per year during the 6-year follow-up. Our data thus suggest that, for unknown reasons, incidence of SUDEP decreases with duration of follow-up. This has implications for patient counseling as well as for the design of studies attempting to assess the effectiveness of an intervention against SUDEP, which clearly needs to include a control group.