title: Population-level response shift: novel implications for research.
abstract: OBJECTIVE
  Response shift is a change in perceived HRQL that occurs as a result of recalibration, reprioritization, or reconceptualization of an individual respondent's internal standards, values, or conceptualization of HRQL.  In this commentary, we suggest that response shift may also occur at the population level, triggered by causes that affect the distribution of individual-level risk.
  
  
  METHODS
  We illustrated the nature and consequences of potential population-level response shift with two examples: the September 11 terror attacks, and the recent denormalization of smoking.
  
  
  RESULTS
  Response shift may occur at the population-level, when a large proportion of the population experiences the shift simultaneously, as a unit, and when the cause of the response shift is a socially significant event or trend. Such catalysts are of a qualitatively different nature than the causes leading to health status changes among individuals, and speak to the determinants affecting the underlying distribution of risk in the population.
  
  
  CONCLUSIONS
  We do not know if population-level causes have actually resulted in response shifts. Nonetheless, response shifts at the population-level may be worthwhile to investigate further, both to assess the validity of research evidence based on the measurement of HRQL in large populations, and as a desirable intermediate outcome in evaluations of population health programs.
authors.affiliation: Department of Public Health Sciences, 2-040 Li Ka Shing Centre for Health Research Innovation, University of Alberta, Edmonton, Alberta, AB, T6G 2E1, Canada.
authors.forename: Darren
authors.initials: D
authors.lastname: Lau
authors.forename: Calypse
authors.initials: C
authors.lastname: Agborsangaya
authors.forename: Fatima Al
authors.initials: FA
authors.lastname: Sayah
authors.forename: Xiuyun
authors.initials: X
authors.lastname: Wu
authors.forename: Arto
authors.initials: A
authors.lastname: Ohinmaa
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Johnson
mesh_terms: D006304:Health Status; D006801:Humans; D036301:Qualitative Research; D011788:Quality of Life / Q000523:psychology*; D047851:September 11 Terrorist Attacks; D012907:Smoking / Q000523:psychology*; D013997:Time Factors
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