title: Association between randomised trial evidence and global burden of disease: cross sectional study (Epidemiological Study of Randomized Trials--ESORT).
abstract: OBJECTIVE
  To determine whether an association exists between the number of published randomised controlled trials and the global burden of disease, whether certain diseases are under-investigated relative to their burden, and whether the relation between the output of randomised trials and global burden of disease can be explained by the relative disease burden in high and low income regions.
  
  
  METHODS
  Cross sectional investigation.
  
  
  METHODS
  All primary reports of randomised trials published in December 2012 and indexed in PubMed by 17 November 2013.
  
  
  METHODS
  Number of trials conducted and number of participants randomised for each of 239 different diseases or injuries; variation in each outcome explainable by total disability adjusted life years (a measure of the overall burden of each disease) and the ratio of disability adjusted life years in low income to high income regions (a measure of whether a disease is more likely to affect people living in high income regions) quantified using multivariable regression.
  
  
  RESULTS
  4190 abstracts were reviewed and 1351 primary randomised trials identified, of which 1097 could be classified using the global burden of disease taxonomy. Total disability adjusted life years was poorly associated with number of randomised trials and number of participants randomised in univariable analysis (Spearman's r=0.35 and 0.33, respectively), although it was a significant predictor in the univariable and multivariable models (P<0.001). Diseases for which the burden was predominantly located in low income regions had sevenfold fewer trials per million disability adjusted life years than diseases predominantly located in high income regions. However, only 26% of the variation in number of trials among diseases could be explained by total disability adjusted life years and the ratio of disability adjusted life years in low income regions to high income regions. Many high income type diseases (for example, neck pain, glomerulonephritis) have proportionally fewer randomised trials compared with low income type diseases (for example, vitamin A deficiency).
  
  
  CONCLUSIONS
  Overall, a weak association existed between global burden of disease and number of published randomised trials. A global observatory for research is needed to monitor and reduce the discordance between the output of randomised trials and global burden of disease.
authors: George Institute for Global Health, University of Oxford, Oxford OX1 3DB, UK cemdin@georgeinstitute.org.uk.
authors: Connor A
authors: CA
authors: Emdin
authors: Centre for Statistics in Medicine, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UKJ Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
authors: Ayodele
authors: A
authors: Odutayo
authors: University of Oxford, Oxford, UK.
authors: Allan J
authors: AJ
authors: Hsiao
authors: University of Oxford, Oxford, UK.
authors: Mubeen
authors: M
authors: Shakir
authors: Centre for Statistics in Medicine, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UKJ Centre d'Epidémiologie Clinique, Université Paris Descartes, INSERM U1153, France.
authors: Sally
authors: S
authors: Hopewell
authors: George Institute for Global Health, University of Oxford, Oxford OX1 3DB, UK.
authors: Kazem
authors: K
authors: Rahimi
authors: Centre for Statistics in Medicine, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UKJ.
authors: Douglas G
authors: DG
authors: Altman
mesh_terms: D017281:Cost of Illness; D003430:Cross-Sectional Studies; D006233:Persons with Disabilities / Q000706:statistics & numerical data; D014943:Global Health / Q000706:statistics & numerical data*; D006801:Humans; D007182:Income / Q000706:statistics & numerical data; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data; D018401:Sample Size
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