Social Jetlag and Excessive Daytime Sleepiness from a Sample of Russian Children and Adolescents

Figures & data

Table 1 Descriptive Statistics of the Sample

	Mean	SD
PDSS score	11.58	5.94
Wake up time school day	7:11	0:41
Wake up time free days	9:28	1:39
Bed time school day	22:43	1:07
Bed time free day	23:29	1:27
Sleep duration school days	8:28	1:18
Sleep duration free days	9:58	1:48
Average sleep duration	9:33	1:27
Midpoint of Sleep school days	2:57	0:40
Midpoint of Sleep free days	4:28	1:16
MSFsc	4:15	1:10
Social jetlag	91	69

Note: Variables are presented as the mean [SD]. Bedtime. wake-up time. sleep duration and mid-sleep times are presented in hours: minutes. Social jetlag is shown in minutes.

Table 2 Factor Loadings of the Single Items Onto the PDSS

	Factor Loadings
Item 1	0.721
Item 2	0.638
Item 3	−0.386
Item 4	0.587
Item 5	0.546
Item 6	0.676
Item 7	0.568
Item 8	0.729

Note: Please note that item 3 is reverse coded and was reversed to calculate the PDSS sum score.

Figure 1 Frequency distribution of PDSS-RUS scores in full sample (A), elementary school (B), middle school (C), and high school (D).

Table 3 Sleep Variables of Schoolchildren in Various Grades

	Elementary School (E)	Middle School (M)	High School (H)
	N=393	N=36	N=50
	Mean (SD)	Mean (SD)	Mean (SD)	Post Hoc p value
Wake-up time school day	7:13 (0:43)	7:05(0:28)	7:04 (0:30)	0.236
Wake -up time free days	9:22 (1:36)	9:57(1:43))	9:52(1:45)	0.022; E<M=H
Bed time school day	22:30(0:58)	23:25 (1:15)	0:01 (1:03)	<0.001; E<M<H
Bed time free day	23:13(1:16)	0:28(1:53)	0:53(1:23)	<0.001; E<M<H
Sleep duration school days	8:43(1:10)	7:40 (1:24)	7:03 (1:07)	<0.001; E>M>H
Sleep duration free days	10:09(1:49)	9:29 (1:26)	8:58 (1:25)	<0.001; E>M>H
Average sleep duration	9:44(1:28)	8:58 (1:14)	8:26 (1:03)	<0.001; E>M=H
Midpoint of Sleep on school days	2:51(0:37)	3:15 (0:39)	3:32 (0:36)	<0.001; E<M<H
Midpoint of Sleep on free days	4:18(1:08)	5:12 (1:39)	5:22 (1:25)	<0.001; E<M=H
Social jetlag	1:26(1:07)	1:57 (1:23)	1:49 (1:06)	0.004; E<M=H
Chronotype(MSFsc)	4:05(1:02)	4:57 (1:34)	5:06 (1:16)	<0.001; E<M=H

Notes: Variables are presented as the mean [SD]. Bedtime wake-up time sleep duration and mid-sleep times are presented in hours: minutes. Social jetlag is shown in minutes. Data were compared using analysis of variance (ANOVA) and post hoc analysis among grades (1st–4th of elementary school. 5th– 8th of middle school and 9–11th of high school).

Table 4 Correlations Between PDSS Scores and Sleep-Wake Variables

		PDSS Score
Age	r	0.098*
	P	0.027
Wake up time school day	r	0.101*
	P	0.026
Wake up time free days	r	0.240**
	P	<0.001
Bedtime school days	r	0.222**
	P	<0.001
Bedtime freedays	r	0.154**
	P	0.001
Sleep duration school days	r	−.138**
	P	0.002
Sleep duration free days	r	0.095*
	P	0.039
Average sleep duration	r	0.047
	P	0.304
Midsleep time school days	r	0.239**
	P	<0.001
Midsleep time free days	r	0.244**
	P	<0.001
Social jetlag	r	0.130**
	P	0.004
Chronotype (MSFsc)	r	0.222**
	P	<0.001

Notes: **Indicates P<0.01, *Indicates P<0.05.

Figure 2 Relationship between daytime sleepiness (PDSS score) and chronotype (MSFsc) and Social Jetlag.

Table 5 Factors Affecting Daytime Sleepiness in Russian School Children, with PDSS Score as Dependent Variable and Age, Sex, Social Jetlag, Average Sleep Duration and Midpoint of Sleep as Independent Variables

	Non Standardized Coefficient	SE	Standardized Beta	T	P
Constant	−62.952	13.305		−4.732	<0.001
Age	0.133	0.124	0.053	1.072	0.284
Sex	0.063	0.532	0.005	0.118	0.906
MSFsc	2.437	0.459	0.477	5.309	<0.001
Social jetlag	−1.607	0.467	−0.309	−3.442	0.001
Average sleep duration	0.705	0.214	0.175	3.295	0.001

Note: Numbers in bold show significant p values.