An unparalleled assessment of the global burden of epilepsy
Authors: W Allen Hauser
Journal: The Lancet Neurology (2019)

The risk of mortality is known to be higher in people with epilepsy than in the general population. Epilepsy is also responsible for considerable disability. In The Lancet Neurology, the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2016 Epilepsy Collaborators provide an unparalleled global assessment of the mortality and morbidity in people with epilepsy of unknown cause.1GBD 2016 Epilepsy CollaboratorsGlobal, regional, and national burden of epilepsy, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016.Lancet Neurol. 2019; (published online Feb 14.)http://dx.doi.org/10.1016/S1474-4422(18)30454-XGoogle Scholar The modelling procedures used by the GBD Collaborators enable estimates for prevalence, mortality, and disability-adjusted life years (DALYs) associated with epilepsy of unknown cause, even for countries for which no data exist. Comorbidity adjustments were made with US hospital claims data. A positive point is that the International Classification of Diseases (ICD) ninth Clinical Modification was used in the USA for most of the period of the study; thus, no adjustment was needed for a new coding system (ICD-10). Unfortunately, mandated coding changes for seizures and epilepsy occurred in the USA over this time, the most important of which was shifting the classification of patients with a code of 780·39 (seizures) to a code of 345·9 (epilepsy) in 2005. This change resulted in a threefold increase in reported hospital stays for epilepsy after 2005 when compared with earlier years. The greatest increase (up to fourfold) was in people aged 50 years or older. However, there was no evidence for a true increase in the prevalence or incidence of epilepsy.2Cardenas VM Roman GC Perez A Hauser WA Why U.S. epilepsy hospital stays rose in 2006.Epilepsia. 2014; 55: 1347-1354Crossref PubMed Scopus (10) Google Scholar The accuracy of adjustments for variation in comorbidities, given such substantial changes in discharges attributable to epilepsy, might therefore be questioned. Another methodological point to consider is that weighting for disability might have been arbitrary and variable across studies, thus precluding comparisons. However, as long as weighting was consistent across time within the study, it should not have affected the results of the comparisons being made.3Ding D Hong Z Wang WZ et al.Assessing the disease burden due to epilepsy by disability adjusted life year in rural China.Epilepsia. 2006; 47: 2032-2037Crossref PubMed Scopus (36) Google Scholar, 4Nord E Uncertainties about disability weights for the Global Burden of Disease study.Lancet Glob Health. 2015; 3: e661-e662Summary Full Text Full Text PDF PubMed Scopus (22) Google Scholar The restriction of this GBD analysis to individuals with epilepsy of unknown cause was reasonable. The consequences of epilepsy following other neurological insults were appropriately assigned to the antecedent cause. However, use of the term idiopathic for the population studied might not have been the best choice given ongoing controversy over the term.5Scheffer IE Berkovic S Capovilla G et al.ILAE classification of the epilepsies: Position paper of the ILAE Commission for Classification and Terminology.Epilepsia. 2017; 58: 512-521Crossref PubMed Scopus (2416) Google Scholar Furthermore, idiopathic, as used in the current study, includes both idiopathic generalised epilepsies (and genetic generalised epilepsies) and cryptogenic epilepsies—groups that were clearly distinguished in the early classifications.6Proposal for revised classification of epilepsies and epileptic syndromes. Commission on Classification and Terminology of the International League Against Epilepsy.Epilepsia. 1989; 30 (No authors listed.): 389-399Crossref PubMed Scopus (5828) Google Scholar These two groups differ by age and, importantly for this study, by mortality and prognosis for seizure remission. Thus, despite few data, calculation of DALYs separately for idiopathic generalised epilepsies and cryptogenic epilepsies would be useful. Future plans for GBD studies include obtaining data from geographical areas with few data available thus far, allowing refinement of estimates. Although this approach might be useful, the current analysis includes papers published over the past 25 years, with data collection for some studies starting in the 1980s. Without a special emphasis on and support for epilepsy data collection in regions with limited research infrastructure, it seems unlikely that substantial new data will be acquired in the near future. There are several additional strategies for future research that would be useful and that the GBD team could facilitate in the meantime. First, the primary audience for this study would seem to be health-care planners and policy makers, not neurologists. The presentation of mortality and prevalence rates in table 1 would be more meaningful to the clinician for making comparisons among geographical areas, as opposed to the numbers of deaths and numbers of prevalent cases as currently presented. Second, the data presented in the GBD analysis provide testable hypotheses. There are few preventive measures likely to alter incidence in people with epilepsy of unknown cause, although DALYs have been significantly reduced (19·4% [95% uncertainty interval 9·0 to 27·6]) over the study period. This reduction occurred despite little change in the number of cases. Investigation of the reasons for these trends would be appropriate. Third, for health-care administrators in countries with time trends opposite to general trends for decreasing mortality and total burden as measured by DALYs (Iceland, Germany, and Denmark), an assessment of the reasons for these differences could be valuable. These three countries have substantial epidemiological data available. It is not clear how many studies from these countries were included in the current study, but validation of the trends should be possible given that the research infrastructure is already in place. Finally, substantially higher age-standardised DALY morbidity exists in low compared with high Socio-demographic Index (SDI) quintile countries, largely because of increased severity of epilepsy in low SDI regions. This finding suggests that interventions such as improved treatment of epilepsy could reduce burden in low SDI regions. The concept is not new, and intervention programmes in rural China, for example, have proved beneficial, leading to government-mandated changes in epilepsy care.7Kwan P Wang W Wu J et al.Long-term outcome of phenobarbital treatment for epilepsy in rural China: a prospective cohort study.Epilepsia. 2013; 54: 537-542Crossref PubMed Scopus (21) Google Scholar, 8Wang W Wu J Dai X et al.Global campaign against epilepsy: assessment of a demonstration project in rural China.Bull World Health Organ. 2008; 86: 964-969Crossref PubMed Scopus (72) Google Scholar Potential candidate sites could be identified from this study where government agencies, administrators, and available infrastructure will enable additional intervention studies. Funds might be used to implement interventions in addition to or instead of collecting additional data. The findings reported in this Article support the need for intervention, and the prevalence-based assessment used by the GBD Collaborators will provide a timely and useful metric to evaluate change. I declare no competing interests. Global, regional, and national burden of epilepsy, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016Despite the decrease in the disease burden from 1990 to 2016, epilepsy is still an important cause of disability and mortality. Standardised collection of data on epilepsy in population representative surveys will strengthen the estimates, particularly in countries for which we currently have no or sparse data and if additional data is collected on severity, causes, and treatment. Sizeable gains in reducing the burden of epilepsy might be expected from improved access to existing treatments in low-income countries and from the development of new effective drugs worldwide. Full-Text PDF Open Access