Table 1. Structure and scoring of the Pittsburgh Sleep Quality Index-Korean version (PSQI-K)

Component	No. of items	Scoring items	Description	Scoring criteria	Score range
C1. Subjective sleep quality	1	#6	Rating of overall sleep quality; direct score from item #6	very good=0, fairly good=1, fairly bad=2, very bad=3	0-3
C2. Sleep latency	2	#2, #5a	Sum of the recoded score for item #2 and the score for item #5a	0=0, 1–2=1, 3–4=2, 5–6=3	0-3
C3. Sleep duration	1	#4	Total hours of actual sleep: direct score from item #4	>7 h=0, 6–7 h=1, 5–6 h=2, <5 h=3	0-3
C4. Habitual sleep efficiency	3	#1, #3, #4	Actual sleep hours (#4) / total hours in bed(#3-#1) × 100	≥85%=0, 75–84%=1, 65–74%=2, <65%=3	0-3
C5. Sleep disturbance	9	#5b to #5j	Sum of scores for 9 items (#5b to #5j) assessing sleep disturbances, such as waking up during the night, getting up to use the bathroom, coughing, and other sleep-related problems	0=0, 1–9=1, 10–18=2, 19–27=3	0-3
C6. Use of sleep medication	1	#7	Frequency of taking medication to sleep; direct score from item #7	none=0, <1/week=1, 1–2/week=2, ≥3/week=3	0-3
C7. Daytime dysfunction	2	#8, #9	Problems staying awake during daily activities and maintaining enthusiasm; sum of #8 and #9	0=0, 1–2=1, 3–4=2, 5–6=3	0-3
Global score	Sum of C1–C7	Total of seven component scores	Higher scores indicate poorer sleep quality	0-21

Note. Item #2 is scored as follows: ≤15 min=0, 16–30 min=1, 31–60 min=2, and >60 min=3. Items #5 and #8 are scored as follows: none=0, <1/week=1, 1–2/week=2, and ≥3/week=3. Item #9 is scored as follows: none=0, slight=1, moderate=2, and severe=3. This Table was adaptied from the appendix scoring guide reported by Sohn et al.(2012).