title: Stability of the Pittsburgh Sleep Quality Index and the Epworth Sleepiness Questionnaires over 1 year in early middle-aged adults: the CARDIA study.
abstract: OBJECTIVE
  To describe the stability of the Pittsburgh Sleep Quality Index (PSQI) and the Epworth Sleepiness Scale (ESS) scores over 1 year among a population-based sample of black and white early middle-aged adults.
  
  
  METHODS
  More than 600 participants, aged 38 to 50 years, from the Chicago site of the Coronary Artery Risk Development in Young Adults (CARDIA) Study.
  
  
  METHODS
  The PSQI and ESS were completed twice, approximately 1 year apart, between 2003 and 2005. Seven PSQI 4-level component scores, a global PSQI score, and the ESS scores were calculated. A PSQI global score greater than 5 was classified as poor quality sleep, and an ESS score greater than 10 was classified as high daytime sleepiness.
  
  
  RESULTS
  The mean+/-SD PSQI score was 5.7+/-3.1 in Year 1 and 5.9+/-3.1 in Year 2. The mean ESS score was 7.4+/-4.3 in Year 1 and 7.2+/-4.2 in Year 2. The Pearson correlation coefficient for the PSQI score in both years in the full sample was .68 and ranged from .54 among black men to .72 among black women. The Pearson correlation coefficient for the ESS score in both years in the full sample was .76 and ranged from .70 among black men to .80 among white men. In the full sample, 76% had the same PSQI dichotomous classification, and 85% had the same ESS dichotomous classification in both years.
  
  
  CONCLUSIONS
  These results suggest that the PSQI and ESS are stable measures of sleep quality and sleepiness over the past year in early middle-aged adults.
authors.affiliation: Department of Health Studies, University of Chicago, 5841 S. Maryland Ave, MC2007, Chicago, IL 60637, USA. kknutson@health.bsd.uchicago.edu
authors.forename: Kristen L
authors.initials: KL
authors.lastname: Knutson
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Rathouz
authors.forename: Lijing L
authors.initials: LL
authors.lastname: Yan
authors.forename: Kiang
authors.initials: K
authors.lastname: Liu
authors.forename: Diane S
authors.initials: DS
authors.lastname: Lauderdale
mesh_terms: D000328:Adult; D044383:Black People / Q000523:psychology; D015331:Cohort Studies; D003327:Coronary Disease / Q000208:ethnology / Q000209:etiology / Q000523:psychology; D006970:Disorders of Excessive Somnolence / Q000175:diagnosis* / Q000208:ethnology / Q000523:psychology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015203:Reproducibility of Results; D012307:Risk Factors; D012893:Sleep Wake Disorders / Q000175:diagnosis* / Q000208:ethnology / Q000523:psychology; D013223:Statistics as Topic; D011795:Surveys and Questionnaires; D044465:White People / Q000523:psychology