Sleep Quality and Cognitive Abilities in the Greek Cohort of Epirus Health Study

Figures & data

Figure 1 Flowchart for the identification of the study population.

Note: Each outcome was determined independent of the other outcomes.

Table 1 Sociodemographic and Lifestyle Characteristics of Epirus Health Study Participants by Level of Sleep Quality

Characteristics	All Participants (Ν=2112)	Sleep Quality^†		p-value
		Good (Ν=1546)	Poor (Ν=566)
Age	46.7 ± 11.4	46.1 ± 11.3	48.1 ± 11.7	<0.001^a
Female	1268 (60.1)	873 (56.5)	395 (69.8)	<0.001^b
Education				<0.001^b
Primary and secondary school*	167 (7.9)	92 (6.0)	75 (13.3)
High school**	590 (28.0)	421 (27.3)	169 (29.9)
Higher education***	1353 (64.1)	1032 (66.8)	321 (56.8)
PSQI score	4.6 ± 2.3	1546 (73.2)	566 (26.8)
BMI	26.5 ± 4.9	26.4 ± 4.9	26.6 ± 4.8	0.498^a
Alcohol consumption				0.153^b
Never	280 (13.3)	201 (13.0)	79 (14.0)
Less than once / month	627 (29.7)	444 (28.7)	183 (32.3)
1–3 times / month	312 (14.8)	237 (15.3)	75 (13.3)
1–2 times / week	628 (29.7)	477 (30.9)	151 (26.7)
Almost everyday	265 (12.6)	187 (12.1)	78 (13.8)

Notes: ^†Sleep Quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) score. Good and poor sleep quality were defined if PSQI ranged between 0–5 and 6–21, respectively. *Elementary school or junior high school, up to 9 years of education. **High school, up to 12 years of education. ***University degree/MSc/PhD/Postdoc, more than 13 years of education. ^aComparisons using t-test. ^bComparisons using x² test. Mean ± standard deviation and frequency (percentage) are presented for continuous and categorical variables, respectively.

Abbreviations: PSQI, Pittsburgh Sleep Quality Index; BMI: body mass index.

Table 2 Results of Multivariable Linear Regressions for the Cross-Sectional Association Between Sleep Quality (Continuous Score) and Cognitive Function (Continuous Score) Among Epirus Health Study Participants

Sleep Quality^†
Cognitive Function Scores	Model 1^a			Model 2^b
	Beta	95% CI	p-value	Beta	95% CI	p-value
Verbal Fluency
Semantic	−0.113	−0.227, 0.001	0.051	−0.109	−0.223, 0.006	0.063
Phonemic	−0.223	−0.550, 0.104	0.182	−0.069	−0.140, 0.002	0.057
Logical Memory
Immediate recall	0.050	−0.039, 0.139	0.273	0.051	−0.039, 0.141	0.264
Delayed recall	0.010	−0.036, 0.056	0.669	0.012	−0.034, 0.058	0.615
Trail Making Test
Part A	0.271	0.050, 0.493	0.016	0.272	0.052, 0.493	0.016
Part B	0.283	−0.069, 0.636	0.115	0.286	−0.063, 0.635	0.108

Notes: ^†Sleep Quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) score. ^aAdjusted for age (continuous), sex, education. ^bAdjusted for age (continuous), sex, education, BMI and alcohol consumption. Bold values indicate statistical significance at the p < 0.05 level.

Abbreviation: CI, Confidence interval.

Table 3 Results of Multivariable Linear Regressions for the Prospective Association Between Sleep Quality (Continuous Score) and Cognitive Function (Continuous Score) Among Epirus Health Study Participants

Sleep Quality^†
Cognitive Function Scores	Model 1^a			Model 2^b
	Beta	95% CI	p-value	Beta	95% CI	p-value
Posner cueing
Total correct	−0.443	−1.339, 0.453	0.330	−0.546	−1.428, 0.337	0.224
Mean reaction time-valid trials	0.008	−0.003, 0.019	0.152	0.006	−0.005, 0.018	0.276
Mean reaction time-invalid trials	−0.002	−0.013, 0.010	0.757	−0.002	−0.014, 0.010	0.759
Emotional word recognition
Total correct	0.183	−0.322, 0.687	0.476	0.144	−0.375, 0.663	0.584
True positive	−0.039	−0.313, 0.235	0.780	−0.016	−0.300, 0.267	0.909
True negative	0.221	−0.112, 0.555	0.191	0.161	−0.175, 0.496	0.345
Corsi block-tapping
Forward	−0.026	−0.177, 0.125	0.734	−0.035	−0.193, 0.123	0.660
Backward	−0.019	−0.172, 0.135	0.811	−0.033	−0.194, 0.129	0.687
Stroop
Total correct	−0.477	−1.568, 0.614	0.389	−0.602	−1.708, 0.504	0.283
Mean reaction time-congruent trials	−0.003	−0.019, 0.013	0.724	−0.002	−0.019, 0.014	0.776
Mean reaction time-incongruent trials	0.010	−0.012, 0.032	0.387	0.013	−0.009, 0.036	0.247

Notes: ^†Sleep Quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) score. ^aAdjusted for age (continuous), sex, education. ^bAdjusted for age (continuous), sex, education, BMI and alcohol consumption.

Abbreviation: CI, Confidence interval.

Table 4 Results of Multivariable Linear Regressions for the Association Between Sleep Quality and Cognitive Function (Continuous Score) with the Interaction Terms by Age Groups and Sex Among Epirus Health Study Participants

Sleep Quality^†
Cognitive Function Scores	Interaction with Age			Interaction with Sex
	Beta	95% CI	p-value	Beta	95% CI	p-value
Verbal Fluency
Semantic	0.001	−0.009, 0.011	0.852	0.017	−0.229, 0.264	0.891
Phonemic	−0.002	−0.008, 0.005	0.607	0.030	−0.123, 0.183	0.701
Logical Memory
Immediate recall	−0.003	−0.011, 0.005	0.439	−0.032	−0.225, 0.162	0.749
Delayed recall	0.000	−0.004, 0.004	0.861	0.029	−0.071, 0.128	0.573
Trail Making Test
Part A	0.013	−0.007, 0.032	0.198	−0.108	−0.581, 0.366	0.655
Part B	0.025	−0.005, 0.056	0.101	0.112	−0.639, 0.863	0.770

Notes: ^†Sleep Quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) score. Adjusted for age (continuous), sex, education, BMI and alcohol consumption.

Abbreviation: CI, Confidence interval.