Relationship between the Pittsburgh Sleep Quality Index and the Epworth Sleepiness Scale in a sleep laboratory referral population

Figures & data

Table 1 Measured parameters within the study population

Variable	Mean	SD	Median	Minimum	Maximum
BMI (kg/m^2)
Total	34.4	8.3	32.8	18.0	66.0
Men	34.1	7.7	32.5	18.4	66.0
Women	35.4	9.7	34.5	18.0	59.0
Age (years)
Total	52.9	13.9	53.0	19.0	90.3
Men	52.3	13.9	52.4	19.0	90.3
Women	54.3	13.9	56.7	23.6	82.1
ESS	9.0	4.8	9.0	0	22.0
PSQI	8.6	4.2	8.0	2.0	19.0
SE%	68.3	21.1	74.5	6.4	97.3
AHI	31.3	36.5	15.5	0	158.8
AI	17.0	12.3	14.0	1.0	72.0
APLM/hour	0.5	1.3	0	0	9.4
RERA/hour	2.1	3.8	0.6	0	22.1

Abbreviations: AHI, Apnea–Hypopnea Index; AI, Arousal Index; APLM, Arousing Periodic Limb Movements; BMI, Body Mass Index kg/m²; ESS, Epworth Sleepiness Scale; PSQI, Pittsburg Sleep Quality Index; RERA, respiratory effort-related arousals; SD, standard deviation; SE, sleep efficiency.

Figure 1 Scatterplot of PSQI and ESS scores.

Abbreviations: ESS, Epworth Sleepiness Scale; PSQI, Pittsburg Sleep Quality Index.

Table 2 Categorical comparisons

Variable	PSQI ≤ 5 (n = 69, 29.2%) n (%)	PSQI > 5 (n = 167, 70.8%) n (%)	Odds ratio (95% CI)	P-value (χ^2)
ESS
≤10	50 (34.2)	96 (65.8)	Referent	0.03
>10	19 (21.1)	71 (78.9)	1.9 (1.1–3.6)

Abbreviations: CI, confidence interval; ESS, Epworth Sleepiness Scale; PSQI, Pittsburg Sleep Quality Index.

Table 3 Association of PSQI with PSG parameters

Covariates	PSQI ≤ 5 {n = 69}		PSQI > 5 {n = 167}		P-value
	Mean (SD)	Median (IQR)	Mean (SD)	Median (IQR)
BMI (kg/m^2)	32.9 (8.2)	31.6 (8.3)	35.1 (8.3)	33.5 (10.4)	0.07*
Age (years)	53.3 (14.8)	54.0 (19.0)	52.7 (13.6)	53.0 (20.0)	0.74*
ESS	8.0 (4.3)	8.0 (7.0)	9.4 (5.0)	9.0 (8.0)	0.04*
SE (%)	70.7 (20.0)	76.4 (24.4)	67.3 (21.5)	72.8 (28.1)	0.26*
AHI	34.0 (35.0)	19.8 (45.2)	30.2 (37.2)	14.1 (34.9)	0.13δ
AI	18.1 (14.2)	13.5 (15.5)	16.6 (11.4)	14.0 (16.0)	0.77δ
APLM/hour	0.5 (1.4)	0 (0.1)	0.4 (1.2)	0 (0)	0.51δ
RERA/hour	2.1 (3.8)	0.5 (2.8)	2.1 (3.8)	0.7 (2.4)	0.61δ

Notes:

* P-value based on t-test;

δ P-value based on Wilcoxon test.

Abbreviations: AHI, Apnea–Hypopnea Index; AI, Arousal Index; APLM, Arousing Periodic Limb Movements; BMI, Body Mass Index kg/m²; ESS, Epworth Sleepiness Scale; IQR, interquartile range; PSQI, Pittsburg Sleep Quality Index; RERA, respiratory effort-related arousals; PSG, polysomnography; SD, standard deviation; SE, sleep efficiency.

Table 4 Association of ESS with PSG parameters

Covariates	ESS ≤ 10 {n = 146}		ESS > 10 {n = 90}		P-value
	Mean (SD)	Median (IQR)	Mean (SD)	Median (IQR)
BMI (kg/m^2)	33.3 (7.9)	32.1 (8.1)	36.2 (8.6)	34.6 (11.7)	0.008*
Age (years)	53.0 (14.3)	54.0 (22.0)	52.6 (13.3)	52.0 (16.0)	0.80*
PSQI	8.2 (4.4)	7.0 (7.0)	9.2 (3.8)	9.0 (6.0)	0.05*
SE (%)	68.7 (21.2)	75.0 (21.3)	67.7 (21.0)	72.4 (32.5)	0.72*
AHI	27.1 (33.1)	13.5 (25.7)	38.1 (40.7)	20.9 (53.0)	0.05δ
AI	18.2 (13.4)	15.0 (16.0)	15.1 (9.9)	13.0 (14.0)	0.11δ
APLM/hour	0.6 (1.3)	0 (0.6)	0.3 (1.2)	0 (0)	0.004δ
RERA/hour	2.1 (3.6)	0.6 (2.5)	2.2 (4.1)	0.7 (2.3)	0.68δ

Notes:

* P-value based on t-test;

δ P-value based on Wilcoxon test.

Abbreviations: AHI, Apnea–Hypopnea Index; AI, Arousal Index; APLM, Arousing Periodic Limb Movements; BMI, Body Mass Index kg/m²; ESS, Epworth Sleepiness Scale; IQR, interquartile range; PSQI, Pittsburg Sleep Quality Index; RERA, respiratory effort-related arousals; PSG, polysomnography; SD, standard deviation; SE, sleep efficiency.

Table 5 Comparison of empirically-defined PSQI/ESS subgroups

Variable	PSQI ≤ 5 and ESS ≤ 10 n = 50 (21.2%)	PSQI ≤ 5 and ESS > 10 n = 19 (8.1%)	PSQI > 5 and ESS ≤ 10 n = 96 (40.7%)	PSQI > 5 and ESS > 10 n = 71 (30.0%)	P-value
Mean BMI (kg/m^2; SD)	32.2 (8.1)	34.7 (8.4)	33.9 (7.8)	36.6 (8.7)	0.02*
BMI (kg/m^2; %)
<25	36.4	9.1	36.4	18.2	0.13^
25–29	18.9	5.7	50.9	24.5
30–34	25.4	11.3	40.8	22.5
35–39	18.0	2.6	33.3	46.1
≥40	13.7	9.8	37.3	39.2
Mean age {years} (SD)	52.6 (15.5)	55.3 (12.9)	53.3 (13.8)	51.8 (13.4)	0.79*
Sex {%}
Female	10.8	3.1	46.1	40.0	0.01^
Male	25.2	9.9	38.6	26.3
Mean SE {%} (SD)	70.6 (20.1)	70.8 (20.1)	67.6 (21.7)	66.9 (21.3)	0.72*
AHI (Median, IQR)	17.6 (33.2)	28.6 (70.9)	12.0 (24.2)	18.2 (47.6)	0.07δ
AI (Median, IQR)	14.5 (16.0)	11.5 (13.0)	15.0 (16.0)	13.0 (15.0)	0.48δ
APLM (Median, IQR)	0 (0.6)	0 (0)	0 (0.6)	0 (0)	0.04δ
RERA (Median, IQR)	0.6 (3.5)	0 (1.0)	0.6 (2.3)	0.7 (3.2)	0.67δ

Notes:

* P-value based on ANOVA;

δ P-value based on Kruskal-Wallis test;

^ P-value based on chi-square test.

Abbreviations: ANOVA, analyses of variance; AHI, Apnea–Hypopnea Index; AI, Arousal Index; APLM, Arousing Periodic Limb Movements; BMI, Body Mass Index kg/m²; ESS, Epworth Sleepiness Scale; IQR, interquartile range; PSQI, Pittsburg Sleep Quality Index; RERA, respiratory effort-related arousals; SD, standard deviation; SE, sleep efficiency.