title: Differing Methods and Definitions Influence DALY estimates: Using Population-Based Data to Calculate the Burden of Convulsive Epilepsy in Rural South Africa.
abstract: BACKGROUND
  The disability adjusted life year (DALY) is a composite measure of disease burden that includes both morbidity and mortality, and is relevant to conditions such as epilepsy that can limit productive functioning. The 2010 Global Burden of Disease (GBD) study introduced a number of new methods and definitions, including a prevalence-based approach and revised disability weights to calculate morbidity and new standard life expectancies to calculate premature mortality. We used these approaches, and local, population-based data, to estimate the burden of convulsive epilepsy in rural South Africa.
  
  
  RESULTS
  Comprehensive prevalence, incidence and mortality data on convulsive epilepsy were collected within the Agincourt sub-district in rural northeastern South Africa between 2008 and 2012. We estimated DALYs using both prevalence- and incidence-based approaches for calculating years of life lived with disability. Additionally, we explored how changing the disease model by varying the disability weights influenced DALY estimates. Using the prevalence-based approach, convulsive epilepsy in Agincourt resulted in 332 DALYs (95% uncertainty interval (UI): 216-455) and 4.1 DALYs per 1,000 individuals (95%UI: 2.7-5.7) annually. Of this, 26% was due to morbidity while 74% was due to premature mortality. DALYs increased by 10% when using the incidence-based method. Varying the disability weight from 0.072 (treated epilepsy, seizure free) to 0.657 (severe epilepsy) caused years lived with disability to increase from 18 (95%UI: 16-19) to 161 (95%UI: 143-170).
  
  
  CONCLUSIONS
  DALY estimates are influenced by both the methods applied and population parameters used in the calculation. Irrespective of method, a significant burden of epilepsy is due to premature mortality in rural South Africa, with a lower burden than rural Kenya. Researchers and national policymakers should carefully interrogate the methods and data used to calculate DALYs as this will influence policy priorities and resource allocation.
authors.affiliation: Studies of the Epidemiology of Epilepsy in Demographic Surveillance Systems (SEEDS), INDEPTH Network, Accra, Ghana.|MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.|Epidemiology and Global Health, Department of Public Health & Clinical Medicine, Umeå University, Umeå, Sweden.
authors.forename: Ryan G
authors.initials: RG
authors.lastname: Wagner
authors.affiliation: Studies of the Epidemiology of Epilepsy in Demographic Surveillance Systems (SEEDS), INDEPTH Network, Accra, Ghana.|KEMRI/Wellcome Trust Research Programme, Centre for Geographic Medicine Research- Coast, Kilifi, Kenya.
authors.forename: Fredrick
authors.initials: F
authors.lastname: Ibinda
authors.affiliation: Studies of the Epidemiology of Epilepsy in Demographic Surveillance Systems (SEEDS), INDEPTH Network, Accra, Ghana.|MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.|Epidemiology and Global Health, Department of Public Health & Clinical Medicine, Umeå University, Umeå, Sweden.
authors.forename: Stephen
authors.initials: S
authors.lastname: Tollman
authors.affiliation: Epidemiology and Global Health, Department of Public Health & Clinical Medicine, Umeå University, Umeå, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Lindholm
authors.affiliation: Studies of the Epidemiology of Epilepsy in Demographic Surveillance Systems (SEEDS), INDEPTH Network, Accra, Ghana.|KEMRI/Wellcome Trust Research Programme, Centre for Geographic Medicine Research- Coast, Kilifi, Kenya.|Neurosciences Unit, Institute for Child Health, University College London, London, United Kingdom.|Department of Psychiatry, University of Oxford, Oxford, United Kingdom.
authors.forename: Charles R
authors.initials: CR
authors.lastname: Newton
authors.affiliation: World Health Organization, Geneva, Switzerland.
authors.forename: Melanie Y
authors.initials: MY
authors.lastname: Bertram
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D017281:Cost of Illness; D004829:Epilepsy, Generalized / Q000453:epidemiology* / Q000523:psychology; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D019057:Quality-Adjusted Life Years; D012424:Rural Population; D013019:South Africa; D013997:Time Factors