title: The Pittsburgh Sleep Quality Index in a multi-ethnic Asian population contains a three-factor structure.
abstract: OBJECTIVE
  The Pittsburgh Sleep Quality Index (PSQI) is a widely used measure for assessing sleep impairment. Although it was developed as a unidimensional instrument, there is much debate that it contains multidimensional latent constructs. We examined the dimensionality of the underlying factor structure of PSQI in Singapore, a rapidly industrialising Asian country with multi-ethnicities representing the Chinese, Malays and Indians.
  
  
  METHODS
  The PSQI was administered through an interviewer-based questionnaire in two separate population-based cross-sectional surveys. An explanatory factor analysis (EFA) was first used to explore the underlying construct of the PSQI in both studies. Then, a confirmatory factor analysis (CFA) was conducted to evaluate an optimal factor model by comparing against other possible models identified in EFA.
  
  
  RESULTS
  There are three correlated yet distinguishable factors that account for an individual's sleep experience from the same best-fit model obtained in both studies: perceived sleep quality, daily disturbances and sleep efficiency. Our three-factor structure of PSQI is superior to the originally intended unidimensional model. Our model also shows the best-fit indices when compared to the previously reported single-factor, two-factor and three-factor (by Cole et al.) models in a multi-ethnic Asian population.
  
  
  CONCLUSIONS
  There is strong evidence that the PSQI contains a three-factor rather than a unidimensional structure in a multi-ethnic Asian population. Scoring the PSQI along their multidimensional perspectives may provide a more accurate understanding of the relationship between sleep impairment and health conditions rather than using a single global score.
authors: Saw Swee Hock School of Public Health, National University of Singapore, Block MD1, 12 Science Drive 2 no. 10-01, Singapore, 117549, Singapore. hiromikwl@gmail.com.
authors: Hiromi W L
authors: HW
authors: Koh
authors: Saw Swee Hock School of Public Health, National University of Singapore, Block MD1, 12 Science Drive 2 no. 10-01, Singapore, 117549, Singapore.
authors: Raymond Boon Tar
authors: RB
authors: Lim
authors: Saw Swee Hock School of Public Health, National University of Singapore, Block MD1, 12 Science Drive 2 no. 10-01, Singapore, 117549, Singapore.
authors: Kee Seng
authors: KS
authors: Chia
authors: Saw Swee Hock School of Public Health, National University of Singapore, Block MD1, 12 Science Drive 2 no. 10-01, Singapore, 117549, Singapore.
authors: Wei Yen
authors: WY
authors: Lim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D044466:Asian People; D003431:Cross-Cultural Comparison; D003430:Cross-Sectional Studies; D018864:Cultural Diversity; D006801:Humans; D008875:Middle Aged; D011594:Psychometrics / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D012846:Singapore; D012893:Sleep Wake Disorders / Q000175:diagnosis* / Q000453:epidemiology / Q000208:ethnology*; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: Confirmatory factor analysis; Explanatory factor analysis; Pittsburgh Sleep Quality Index; Population-based cross-sectional surveys; Singapore; Sleep impairment
references: J Sleep Res. 2011 Mar;20(1 Pt 1):110-6
references: 20561174
references: Sleep Med. 2010 Jan;11(1):69-74
references: 19410512
references: Sleep. 2006 Jan;29(1):112-6
references: 16453989
references: Eur Arch Psychiatry Clin Neurosci. 1993;242(6):329-36
references: 8323982
references: Sleep. 1991 Oct;14(5):392-8
references: 1759091
references: Sleep. 2000 Feb 1;23(1):41-7
references: 10678464
references: Singapore Med J. 1996 Jun;37(3):282-4
references: 8942230
references: Sleep. 2011 Jul 01;34(7):859-67
references: 21731135
references: Gac Med Mex. 2008 Nov-Dec;144(6):491-6
references: 19112721
references: Sleep Med. 2007 Apr;8(3):266-70
references: 17368977
references: Accid Anal Prev. 2013 Oct;59:618-22
references: 23973762
references: J Psychosom Res. 1998 Jul;45(1):5-13
references: 9720850
references: J Psychosom Res. 2012 Feb;72(2):111-3
references: 22281451
references: J Psychiatr Res. 2008 Nov;43(1):48-54
references: 18374943