Epilepsy affects approximately 22% of people with learning disabilities, with the likelihood of epilepsy increasing with the severity of the learning disability (Robertson et al., 2015b). This compares with a prevalence rate of approximately 1% in the general population (Joint Epilepsy Council of the UK and Ireland, 2011).
Epilepsy in the general population is associated with an increased risk of mortality (Nevalainen et al., 2014) and it has been well-documented that people with learning disabilities typically die at a younger age than the general population (CIPOLD, 2013). Therefore studies investigating mortality in people with learning disabilities and epilepsy are much-needed. Robertson et al., 2015a aimed to systematically review this body of literature.
Electronic searches were performed on several databases to search for journal articles reporting mortality in people with learning disabilities and epilepsy. To be included in the systematic review, journal articles had to be peer-reviewed, written in English and published from 1990 onwards.
They also had to be primary research which presented a comparative statistic on mortality in people with learning disabilities and epilepsy compared to people with learning disabilities without epilepsy, people with epilepsy without learning disabilities or the general population.
Research involving people with Down syndrome was permitted but other specific syndromes were excluded, as were case studies or case series and research involving babies up to 28 days old.
The authors took steps to ensure that all relevant studies were identified, for example by searching their personal collections, the reference lists of key book chapters and the reference lists of articles meeting the inclusion criteria.
Sixteen articles met the inclusion criteria. There were differences in the characteristics of the samples and the definitions of epilepsy across the 16 studies so a meta-analysis was not possible. The review reports all statistics related to all cause mortality and specific causes of death. The authors present a detailed discussion of the 16 studies, which will be summarised here.
The most common comparison involved cohorts of people with learning disabilities, some of whom had epilepsy and some of whom did not. In studies which compared these two groups, the people with learning disabilities and epilepsy typically had an increased risk of mortality.
When compared to the general population, people with learning disabilities had an increased risk of mortality, and this was higher for people with learning disabilities and epilepsy. In samples where all participants had epilepsy, there was an increased risk of mortality for those who also had a learning disability compared to those who did not.
Some studies looked at factors such as type and frequency of seizures and found that more severe seizure types and more frequent seizures were associated with an increased risk of mortality for people with learning disabilities and epilepsy.
Some studies investigated the causes of death for people with learning disabilities and epilepsy. It would be expected that this group would be at increased risk for death due to seizures or convulsions than people with learning disabilities without epilepsy, but there was also an increased risk for death due to other causes, for example accidental drowning. It is likely that accidental drowning and other causes are also linked to the presence of epilepsy. Sudden unexpected death in epilepsy (SUDEP) appeared to be more common in people with learning disabilities than the general population.
People with learning disabilities have an increased risk of mortality compared to general population, and this increases if epilepsy is also present. Although the magnitude of this risk varies from study to study, it is likely to be two or more times greater for people with learning disabilities and epilepsy than for a similar group of people with learning disabilities without epilepsy. Similarly the risk for people with learning disabilities and epilepsy is greater than for those with epilepsy and no learning disability.
Mortality is also associated with more severe and/or frequent seizures. The findings on cause of death suggest that accidental drowning and SUDEP could be particular issues for people with learning disabilities and epilepsy, but further research is needed.
Strengths and limitations
As would be expected from a systematic review, the authors clearly outline their methods including the search terms, sources that were searched and number of papers found at the different stages. This is transparent and helpful for readers.
Although different ratio statistics are used in the different studies to compare mortality, e.g. standardised mortality ratio and hazard ratio, the authors provide a clear description of each statistic and are clear about which study uses which statistic.
The papers found in the systematic review are of varying quality, and although the systematic review does not set out to judge quality, descriptions of the studies in the table and in the text offer a starting point for a reader to make their own judgements.
The criteria for establishing whether a person had epilepsy varied from study to study and some studies recruited from specific settings or populations therefore affecting the characteristics of their sample. More carefully-controlled studies with clearly articulated methods and criteria for epilepsy and learning disability are needed. If more high-quality studies are conducted then a meta-analysis would be a helpful next step.
The authors highlight a number of limitations with their study. A particularly important issue is that all studies were from high income countries, therefore low and middle-income countries are not represented.
The authors’ recent publication on prevalence of epilepsy in learning disability also found a relative lack of research from low and middle-income countries (Robertson et al., 2015b) and so highlights a need for studies in epilepsy and learning disabilities in a wide range of countries.
It is clear that people with learning disabilities and epilepsy have an increased risk of mortality. It appears that this risk is associated with seizure severity and frequency . Although the presence of epilepsy may carry an inherent risk, if seizures are controlled it may be that the risk decreases.
Further research is needed to investigate this but it does suggest the particular importance of these findings for those individuals with learning disabilities who have refractory seizures.
The causes of death in people with learning disabilities and epilepsy need further investigation as this may shed light on how to prevent avoidable deaths. High quality data is needed, which comprehensively records details about learning disability, epilepsy and cause of death.
This echoes the recommendation by the Confidential Inquiry (CIPOLD, 2013) that improved collection of standardised mortality data about people with learning disabilities is needed.
Robertson, J., Hatton, C., Emerson, E., & Baines, S. (2015a). Mortality in people with intellectual disabilities and epilepsy: A systematic review. Seizure , 29, 123-133. [abstract]
CIPOLD (2013) Confidential Inquiry into premature Deaths of People with Learning Disabilities (CIPOLD): Final Report. Retrieved 8th January 2015
Joint Epilepsy Council of the UK and Ireland (2011). Epilepsy prevalence, incidence and other statistics. Retrieved 31st March 2015
Nevalainen, O., Ansakorpi, H., Simola, M., Raitanen, J., Isojärvi, J., Artama, M., & Auvinen, A. (2014). Epilepsy-related clinical characteristics and mortality: A systematic review and meta-analysis. Neurology, 83(21), 1968-1977. doi: 10.1212/WNL.0000000000001005
Robertson, J., Hatton, C., Emerson, E., & Baines, S. (2015b). Prevalence of epilepsy among people with intellectual disabilities and epilepsy: A systematic review. Seizure , 29, 45-62. Doi:10.1016/j.seizure.2015.03.016