Development of the Sleep Quality Scale

YI, HYERYEON
SHIN, KYUNGRIM
SHIN, CHOL

¹Institute of Human Genomic Study, College of Medicine, Korea University, Seoul, Republic of Korea
²College of Nursing Science, Ewha Womans University, Seoul, Republic of Korea
³Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Korea University Ansan Hospital, Ansan, Republic of Korea

Correspondence: Chol Shin, MD, PhD, FCCP, Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Korea University Ansan Hospital, 516, Gojan 1-dong, Danwon-gu, Ansan-si, Gyeonggi-do 425-707, Republic of Korea. Tel.: +82-31-412-5603; fax: +82-31-412-5604; e-mail: [email protected]

Accepted in revised form 26 June 2006; received 22 December 2005

Journal of Sleep Research 15(3):p 309-316, September 2006.

SUMMARY

Sleep quality affects health and the overall quality of life. As the factors that influence sleep quality and their relative importance vary among individuals, a self-report method is essential. Although various questionnaires have been used to assess sleep quality, few all-inclusive assessment scales have been developed. Therefore, the purpose of this study was to develop an instrument for measuring sleep quality and to study its validity and reliability. A Sleep Quality Scale (SQS) was developed using item analysis and factor analysis on items with content validity. SQS, composed of 28 items and six factors, accounted for 62.6% of the total variance. The difference of SQS score between insomniacs and normal subjects confirmed the construct validity (t = −13.8, P = 0.000). Concurrent validity was identified by the significant correlation of SQS with the Pittsburgh Sleep Quality Index (r = 0.72, P = 0.000). The Cronbach's alpha coefficient was 0.92 for internal consistency and the correlation coefficient was 0.81 for test–retest reliability at a 2-week interval. The developed SQS was therefore confirmed to be a valid and reliable instrument for the comprehensive assessment of sleep quality.