title: Relationship of meeting physical activity guidelines with quality-adjusted life-years.
abstract: OBJECTIVE
  The quality-adjusted life-year (QALY) is a standard outcome measure used in cost-effectiveness analyses. This study investigates whether attainment of federal physical activity guidelines is associated with higher QALY estimates among adults with or at an increased risk for knee osteoarthritis.
  
  
  METHODS
  This is a prospective study of 1794 Osteoarthritis Initiative participants. Physical activity was measured using accelerometers at baseline. Participants were classified as (1) Meeting Guidelines [≥150min of moderate-to-vigorous (MV) activity per week acquired in sessions ≥10min], (2) Insufficiently Active (≥1 MV session[s]/week but below the guideline), or (3) Inactive (zero MV sessions/week). A health-related utility score was derived from participant responses to the 12-item Short-Form Health Survey at baseline and 2 years later. The QALY was calculated as the area under utility curve over 2 years. The relationship of physical activity level to median QALY adjusted for socioeconomic and health factors was estimated using quantile regression.
  
  
  RESULTS
  Relative to the Inactive group, median QALYs over 2 years were significantly higher for the Meeting Guidelines (0.112, 95% CI: 0.067-0.157) and Insufficiently Active (0.058, 95% CI: 0.028-0.088) groups, controlling for socioeconomic and health factors.
  
  
  CONCLUSIONS
  We found a significant graded relationship between greater physical activity level and higher QALYs. Using the more conservative estimate of 0.058, if an intervention could move someone out of the Inactive group and costs <$2900 over 2 years, it would be considered cost effective. Our analysis supports interventions to promote physical activity even if recommended levels are not fully attained.
authors: Northwestern University Feinberg School of Medicine, Department of Medicine, 251 E. Huron St Suite 3-150, Chicago, IL 60611. Electronic address: kai-sun@northwestern.edu.
authors: Kai
authors: K
authors: Sun
authors: Northwestern University Feinberg School of Medicine, Department of Medicine, 251 E. Huron St Suite 3-150, Chicago, IL 60611.
authors: Jing
authors: J
authors: Song
authors: Northwestern University Feinberg School of Medicine, Department of Medicine, 251 E. Huron St Suite 3-150, Chicago, IL 60611.
authors: Larry M
authors: LM
authors: Manheim
authors: Northwestern University Feinberg School of Medicine, Department of Medicine, 251 E. Huron St Suite 3-150, Chicago, IL 60611.
authors: Rowland W
authors: RW
authors: Chang
authors: University of Arizona School of Medicine, Department of Medicine, Phoenix, AZ.
authors: Kent C
authors: KC
authors: Kwoh
authors: Northwestern University Feinberg School of Medicine, Department of Medicine, 251 E. Huron St Suite 3-150, Chicago, IL 60611; College of Nursing, Rush University, Department of Adult and Gerontological Nursing, Chicago.
authors: Pamela A
authors: PA
authors: Semanik
authors: Brown University School of Medicine, Department of Family Medicine, Providence, RI.
authors: Charles B
authors: CB
authors: Eaton
authors: Northwestern University Feinberg School of Medicine, Department of Medicine, 251 E. Huron St Suite 3-150, Chicago, IL 60611.
authors: Dorothy D
authors: DD
authors: Dunlop
mesh_terms: D061725:Accelerometry; D000368:Aged; D003362:Cost-Benefit Analysis; D005260:Female; D017408:Guidelines as Topic / Q000592:standards*; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000191:economics / Q000453:epidemiology* / Q000503:physiopathology / Q000517:prevention & control; D017063:Outcome Assessment, Health Care; D011446:Prospective Studies; D019057:Quality-Adjusted Life Years; D012044:Regression Analysis; D012307:Risk Factors; D012959:Socioeconomic Factors
keywords: cost effectiveness analysis; knee osteoarthritis; physical activity guidelines; quality adjusted life years