Mortality rate, risk factors, and causes of death in people with epilepsy and intellectual disability

The extent to which co-occurring intellectual disability influences mortality in people with epilepsy is largely unknown. This study compares mortality rates in people with epilepsy with and without intellectual disability and investigates causes of death and risk factors for mortality.

This retrospective cohort study used linked population-based administrative datasets to derive a cohort of people with epilepsy admitted to hospital from 2005-2015 in New South Wales, Australia. We calculated mortality rates for those with and without intellectual disability and compared them by estimating relative mortality risks with modified Poisson regression. Leading causes of death were summarised. We investigated risk factors for death in people with intellectual disability by fitting Poisson regression.

Of 28500 people hospitalised with an epilepsy diagnosis, 6029 had intellectual disability, 863 (14.3%) of whom died during follow-up. Sex and age-adjusted relative mortality risks showed that people with intellectual disability had higher mortality than those without, with the highest risk in females and peaking at age 5 (males: 1.88, 95%CI 1.28-2.48; females: 2.73, 95%CI 1.84-3.62), then decreasing with age. Neurological, respiratory, and endocrine, nutritional, and metabolic disorders were overrepresented causes of death in people with intellectual disability. The risk factors for death were older age, disability service use and several specific comorbidities.

Children and young adults with epilepsy and intellectual disability are at greater risk of dying than those with epilepsy alone. Our data highlight the potential to reduce the excess risk by improved management of epilepsy and comorbid conditions.