title: Comparing the SF-12 and SF-36 health status questionnaires in patients with and without obesity.
abstract: OBJECTIVE
  To assess how well the SF-36, a well-validated generic quality of life (QOL) instrument, compares with its shorter adaptation, the SF-12, in capturing differences in QOL among patients with and without obesity.
  
  
  METHODS
  We compared the correlation between the physical (PCS) and mental (MCS) component summary measures of the SF-12 and SF-36 among 356 primary care patients using Pearson coefficients (r) and conducted linear regression models to see how these summary measures captures the variation across BMI. We used model R2 to assess qualitatively how well each measure explained the variation across BMI.
  
  
  RESULTS
  Correlations between SF-12 and SF-36 were higher for the PCS in obese (r = 0.89) compared to overweight (r = 0.73) and normal weight patients (r = 0.75), p < 0.001, but were similar for the MCS across BMI. Compared to normal weight patients, obese patients scored 8.8 points lower on the PCS-12 and 5.7 points lower on the PCS-36 after adjustment for age, sex, and race; the model R2 was higher with PCS-12 (R2 = 0.22) than with PCS-36 (R2 = 0.16). BMI was not significantly associated with either the MCS-12 or MCS-36.
  
  
  CONCLUSIONS
  The SF-12 correlated highly with SF-36 in obese and non-obese patients and appeared to be a better measure of differences in QOL associated with BMI.
authors.affiliation: Division of General Medicine and Primary Care, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA. cwee@bidmc.harvard.edu
authors.forename: Christina C
authors.initials: CC
authors.lastname: Wee
authors.forename: Roger B
authors.initials: RB
authors.lastname: Davis
authors.forename: Mary Beth
authors.initials: MB
authors.lastname: Hamel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009765:Obesity; D011788:Quality of Life; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires