title: Effect of adding a sleep dimension to the EQ-5D descriptive system: a "bolt-on" experiment.
abstract: The generic preference-based measures (GPBMs) of health have been widely used to obtain health utility scores for calculating quality-adjusted life-years (QALYs) for economic evaluations. It has been recognized that GPBMs may miss relevant or important dimensions of health for some specific medical conditions. The objective of this study is to explore the effect of extending the current EQ-5D descriptive system by adding a sleep dimension.
  
  
  
  A new instrument, EQ-5D+Sleep, is proposed by adding a sleep dimension to the EQ-5D. Based on an orthogonal design, 18 EQ-5D+Sleep states and EQ-5D states were selected and a valuation study was undertaken whereby 160 members of the generic public in South Yorkshire, UK, were interviewed using time tradeoff (TTO). Econometric models have been fitted to the data. Two null hypotheses were tested: 1) the coefficient for the sleep dimension is not significant; and 2) the inclusion of the sleep dimension has no impact on the way people value the original dimensions of EQ-5D.
  
  
  
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  The results support these two null hypotheses. There seems to be no benefit to adding a sleep dimension to the EQ-5D. Research is required to explore the method of adding dimensions to existing descriptive systems of health.
authors.affiliation: Brunel University, Health Economics Research Group, Uxbridge, UK (YY).
authors.forename: Yaling
authors.initials: Y
authors.lastname: Yang
authors.affiliation: School of Health and Related Research, University of Sheffield, Sheffield, UK (JB, AT)
authors.forename: John
authors.initials: J
authors.lastname: Brazier
authors.affiliation: School of Health and Related Research, University of Sheffield, Sheffield, UK (JB, AT)
authors.forename: Aki
authors.initials: A
authors.lastname: Tsuchiya
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D019057:Quality-Adjusted Life Years; D012890:Sleep; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: EQ-5D; QALYs; add-on; health state valuation; sleep