Seasonality as a risk factor for sudden unexpected death in epilepsy: a study in a large cohort

We attempted to establish whether month and season, or lunar phase, are risk factors for sudden unexpected death in epilepsy (SUDEP), as these have all been suggested as potential risk factors.

We used the dataset of the National Sentinel Clinical Audit of Epilepsy-Related Death; all death certificates of people who died in England and Wales between September 1999 and August 2000 and in which epilepsy was mentioned were reviewed. We identified people who probably died of SUDEP during that time. We compared the number of observed SUDEP cases with those expected according to month of death, season of death, minimum external temperature, mean external temperature, and lunar phase.

Of 2,412 deaths, we identified 409 probable SUDEPs. We found no evidence for an association between either mean temperature group or minimum temperature group and SUDEP, although there appeared to be a slight excess of sudden deaths in the coldest (mean temperature) groups. We also found no association between SUDEP and month, season, or lunar phase.

Some causes of death appear to be related to temperature, but we found no convincing evidence to support a link between temperatures or seasons and sudden unexpected death in epilepsy. It is important to identify risk factors for SUDEP, but it is also important that evidence is established before hypotheses are accepted.