Sleep and Breathing

, Volume 19, Issue 4, pp 1147–1154 | Cite as

The Pittsburgh Sleep Quality Index in a multi-ethnic Asian population contains a three-factor structure

  • Hiromi W. L. Koh
  • Raymond Boon Tar Lim
  • Kee Seng Chia
  • Wei Yen Lim
Original Article
First Online:
Received:
Revised:
Accepted:

Abstract

Purpose

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.

Conclusion

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.

Keywords

Confirmatory factor analysis Explanatory factor analysis Pittsburgh Sleep Quality Index Population-based cross-sectional surveys Singapore Sleep impairment 
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Notes

Acknowledgments

The Singapore Health (SH) survey is funded by the Ministry of Health, Singapore. The funder did not play a role in the design, conduct or analysis of the study as well as the drafting of this manuscript. The authors would also like to thank the group of Community Health Project (CHP) medical students of year 2012 from the National University of Singapore (NUS) for going out to conduct the surveys to collect data for the Queenstown study. We would also like to gratefully acknowledge Dr. Choi Hyungwon (NUS) for reading and providing editorial comments for our manuscript.

Ethical standards

Ethics review requirement was waived by the National University of Singapore (NUS) Institutional Review Board (IRB) as anonymous data was collected for the Queenstown study. For SH 2012, ethics was reviewed and approved by the NUS IRB prior to implementation. All subjects had given their informed consent prior to their inclusion in the study.

Conflict of interest

The authors declare that they have no competing interests.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Hiromi W. L. Koh
    • 1
  • Raymond Boon Tar Lim
    • 1
  • Kee Seng Chia
    • 1
  • Wei Yen Lim
    • 1
  1. 1.Saw Swee Hock School of Public HealthNational University of SingaporeSingaporeSingapore

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