Unraveling the role of dysfunctional sleep beliefs: How chronotype shapes sleep quality and academic success in medical students

Table 1 Grade Point Average, Pittsburgh Sleep Quality Index, Dysfunctional Beliefs and Attitudes about Sleep Scale, and Morningness-Eveningness Questionnaire: Descriptives and normality by chronotype

	MEQ type	Mean	SD	Min	Max	Skewness		Kurtosis
						Skew	SE	Kurt	SE
GPA	Evening-type	2.93	0.64	0.10	3.80	-1.49	0.30	4.75	0.59
	Morning-type	3.14	0.43	2.10	3.90	-0.38	0.31	-0.27	0.60
	Intermediate-type	3.19	0.49	1.70	4.20	-0.66	0.32	0.75	0.63
	All	3.08	0.54	0.10	4.20	-1.26	0.18	4.33	0.36
PSQI	Evening-type	16.99	2.44	14.00	23.00	0.72	0.30	-0.30	0.59
	Morning-type	17.70	2.56	13.00	25.00	0.28	0.31	0.09	0.60
	Intermediate-type	17.21	2.32	10.00	22.00	-0.11	0.32	0.88	0.63
	All	17.30	2.45	10.00	25.00	0.34	0.18	0.04	0.36
DBAS	Evening-type	89.34	24.92	18.00	160.00	0.38	0.30	1.15	0.59
	Morning-type	92.64	22.45	19.00	136.00	-0.49	0.31	0.79	0.60
	Intermediate-type	93.57	21.26	49.00	150.00	0.14	0.32	0.66	0.63
	All	91.75	22.96	18.00	160.00	0.02	0.18	0.80	0.36
MEQ	Evening-type	45.12	4.80	22.00	49.00	-3.02	0.30	11.73	0.59
	Morning-type	57.11	2.61	54.00	63.00	0.63	0.31	-0.49	0.60
	Intermediate-type	51.45	1.17	50.00	53.00	0.10	0.32	-1.48	0.63
	All	51.09	5.99	22.00	63.00	-1.03	0.18	3.81	0.36

PSQI: Pittsburgh Sleep Quality Index; GPA: Grade Point Average; DBAS: Dysfunctional Beliefs and Attitudes about Sleep Scale; Morningness-Eveningness Questionnaire.

Table 2 Correlation coefficients among Grade Point Average, Pittsburgh Sleep Quality Index, Dysfunctional Beliefs and Attitudes about Sleep Scale, and Morningness-Eveningness Questionnaire by chronotype

Variables	Evening-type	Morning-type	Intermediate-type	All
GPA-PSQI	-0.30a	-0.13	-0.15	-0.18a
GPA-DBAS	-0.04	-0.13	0.02	-0.03
GPA-MEQ	-0.12	0.07	-0.02	0.11
PSQI-DBAS	0.33b	0.47c	0.33a	0.38c
PSQI-MEQ	-0.21	-0.14	0.02	0.02
DBAS-MEQ	-0.27a	-0.17	0.09	-0.05

^aP < 0.05.

^bP < 0.01.

^cP < 0.001.

GPA: Grade Point Average; PSQI: Pittsburgh Sleep Quality Index; DBAS: Dysfunctional Beliefs and Attitudes about Sleep Scale; MEQ: Morningness-Eveningness Questionnaire.

Table 3 Mediation analysis of Dysfunctional Beliefs and Attitudes about Sleep Scale, Pittsburgh Sleep Quality Index, and Grade Point Average by chronotype

	Type	Effect	Est	SE	95%CI		β	Z	P value
					Lower	Upper
E	Indirect	DBAS ⇒ PSQI ⇒ GPA	-0.00	0.00	-0.01	0.00	-0.10	-1.88	0.06
	Component	DBAS ⇒ PSQI	0.03	0.01	0.01	0.05	0.33	2.80	0.01
		PSQI ⇒ GPA	-0.08	0.03	-0.15	-0.02	-0.32	-2.54	0.01
	Direct	DBAS ⇒ GPA	0.00	0.00	-0.00	0.01	0.06	0.48	0.63
	Total	DBAS ⇒ GPA	-0.00	0.00	-0.01	0.01	-0.04	-0.35	0.72
M	Indirect	DBAS ⇒ PSQI ⇒ GPA	-0.00	0.00	-0.00	0.00	-0.04	-0.57	0.57
	Component	DBAS ⇒ PSQI	0.05	0.01	0.03	0.08	0.47	4.19	< 0.001
		PSQI ⇒ GPA	-0.01	0.02	-0.06	0.03	-0.08	-0.57	0.57
	Direct	DBAS ⇒ GPA	-0.00	0.00	-0.01	0.00	-0.09	-0.64	0.52
	Total	DBAS ⇒ GPA	-0.00	0.00	-0.01	0.00	-0.13	-1.03	0.31
I	Indirect	DBAS ⇒ PSQI ⇒ GPA	-0.00	0.00	-0.00	0.00	-0.06	-1.10	0.27
	Component	DBAS ⇒ PSQI	0.04	0.01	0.01	0.06	0.33	2.59	0.01
		PSQI ⇒ GPA	-0.04	0.03	-0.09	0.02	-0.17	-1.21	0.23
	Direct	DBAS ⇒ GPA	0.00	0.00	-0.00	0.01	0.07	0.50	0.61
	Total	DBAS ⇒ GPA	0.00	0.00	-0.01	0.01	0.02	0.11	0.91
All	Indirect	DBAS ⇒ PSQI ⇒ GPA	-0.00	0.00	-0.00	-0.00	-0.07	-2.27	0.02
	Component	DBAS ⇒ PSQI	0.04	0.01	0.03	0.05	0.38	5.52	< 0.001
		PSQI ⇒ GPA	-0.04	0.02	-0.08	-0.01	-0.20	-2.49	0.01
	Direct	DBAS ⇒ GPA	0.00	0.00	-0.00	0.00	0.04	0.52	0.60
	Total	DBAS ⇒ GPA	-0.00	0.00	-0.00	0.00	-0.03	-0.45	0.66

E: Evening-type; M: Morning-type; I: Intermediate-type.