title: Breaking the silence: exploring the potential effects of explicit instructions on incorporating income and leisure in TTO exercises.
abstract: OBJECTIVE
  An underexplored question in the debate on incorporating productivity costs as costs or effects in a cost-effectiveness (CE) analysis is whether people include effects of ill health on income in health state valuations (HSV). The same holds for the actual inclusion in HSV of the effects of ill health on leisure. This study aims to test whether respondents to HSV using time trade-off (TTO) questions include income and leisure effects without instructions. Moreover, it tests the consequences of explicit instructions to include or exclude income effects.
  
  
  METHODS
  Three questionnaires were administered among the general public. Respondents were asked to value three distinct EuroQol descriptive system health states using TTO. In version 1, respondents were asked afterwards whether they included income effects. In versions 2 and 3, respondents were instructed upfront to include or exclude income effects. They were furthermore asked whether they included leisure effects.
  
  
  RESULTS
  A total of 222 respondents completed the questionnaire. In version 1, 64% of the respondents spontaneously included income effects, not resulting in differences in mean valuations. In versions 2 and 3, 88% included leisure time, resulting in a significantly lower TTO value in one health state. With explicit instructions, respondents instructed to include income gave lower HSV for the worst health state presented.
  
  
  CONCLUSIONS
  Respondents in our sample did not consistently include income effects and leisure effects. Including income effects only had (some) effect on TTO valuations after an explicit instruction. If these results are confirmed in future research, this implies that income effects may be best captured on the cost-side of the CE ratio. Spontaneous inclusion or exclusion of leisure time appeared to be more influential.
authors.affiliation: Department of Health Policy and Management, Erasmus University/Erasmus MC, Rotterdam, The Netherlands. h.krol@erasmusmc.nl
authors.forename: Marieke
authors.initials: M
authors.lastname: Krol
authors.forename: Pedram
authors.initials: P
authors.lastname: Sendi
authors.forename: Werner
authors.initials: W
authors.lastname: Brouwer
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D017281:Cost of Illness; D003362:Cost-Benefit Analysis; D005260:Female; D007722:Health Knowledge, Attitudes, Practice; D006304:Health Status; D006801:Humans; D007182:Income; D007899:Leisure Activities / Q000191:economics*; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D011795:Surveys and Questionnaires; D055815:Young Adult