title: Stability of normative data for the SF-36: results of a three-year prospective study in middle-aged Canadians.
abstract: BACKGROUND
  The SF-36 is widely used to assess health-related quality of life (HRQOL), but with few longitudinal studies in healthy populations, it is difficult to quantify its natural history. This is important because any measure of change following an intervention may be confounded by natural changes in HRQOL. This paper assesses mean changes in SF-36 scores over a 3-year period in men and women between the ages of 40 and 59 years at baseline.
  
  
  METHODS
  Subjects were randomly selected from nine Canadian cities. Mean SF-36 changes over a 3-year period (1996/1997-1999/2000) were calculated for each gender within 5-year age categories. Multiple imputation was used to correct for potential bias due to missing data.
  
  
  RESULTS
  The baseline cohort included 1,974 women and 975 men between 40 and 59 years. Mean changes in HRQOL tended to be small. Women demonstrated small average declines in 22 of the 32 age and domain groupings (4 age groups, 8 SF-36 domains) while men showed declines in 14/32. Most participants stayed within 10 points of their original baseline score.
  
  
  CONCLUSIONS
  Mean SF-36 scores change only slightly over three years in middle-aged Canadians, although there is much individual variation. It may be necessary to adjust for the natural evolution of SF-36 scores when interpreting results from longitudinal studies.
authors.affiliation: Clinical Research Centre, Kingston General Hospital and Department of Community Health and Epidemiology, Queen's University, Kingston, ON. hopmanw@kgh.kari.net
authors.forename: Wilma M
authors.initials: WM
authors.lastname: Hopman
authors.forename: Claudie
authors.initials: C
authors.lastname: Berger
authors.forename: Lawrence
authors.initials: L
authors.lastname: Joseph
authors.forename: Tanveer
authors.initials: T
authors.lastname: Towheed
authors.forename: Elizabeth
authors.initials: E
authors.lastname: vandenKerkhof
authors.forename: Tassos
authors.initials: T
authors.lastname: Anastassiades
authors.forename: Ann
authors.initials: A
authors.lastname: Cranney
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Adachi
authors.forename: George
authors.initials: G
authors.lastname: Loannidis
authors.forename: Suzette
authors.initials: S
authors.lastname: Poliquin
authors.forename: Jacques P
authors.initials: JP
authors.lastname: Brown
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Murray
authors.forename: David A
authors.initials: DA
authors.lastname: Hanley
authors.forename: Emmanuel A
authors.initials: EA
authors.lastname: Papadimitropoulos
authors.forename: Alan
authors.initials: A
authors.lastname: Tenenhouse
mesh_terms: D017677:Age Distribution; D002170:Canada / Q000453:epidemiology; D005260:Female; D006304:Health Status; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011788:Quality of Life; D012015:Reference Standards; D015203:Reproducibility of Results; D017678:Sex Distribution; D011795:Surveys and Questionnaires