Table 6.

Descriptive statistics and correlations for primary PSQI indices of sleep quality, BDI-II score, and HRV during bedtime period.

Variable	M ±SD	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
PSQI component scores
1. Subjective sleep quality	1.04 ± 0.72	1
2. Sleep latency	0.85 ± 0.87	0.554**	1
3. Sleep duration	0.79 ± 0.50	0.269*	0.158	1
4. Habitual sleep efficiency	0.10 ± 0.34	0.157	0.091	0.121	1
5. Sleep disturbance	0.96 ± 0.49	0.374**	0.339**	0.173	0.137	1
6. Use of sleeping medication	0.14 ± 0.51	0.273*	0.341**	0.300*	0.095	0.230	1
7. Daytime dysfunction	1.42 ± 0.95	0.511**	0.398**	0.204	0.187	0.330**	0.389**	1
8. PSQI global score	5.29 ± 2.84	0.769**	0.763**	0.396**	0.259*	0.535**	0.454**	0.774**	1
9. BDI-II scores	8.26 ± 8.61	0.555**	0.383**	0.191	0.147	0.372**	0.288*	0.663**	0.617**	1
10. SDNN	116.21 ± 30.99	−0.047	−0.117	−0.053	0.064	−0.317**	−0.044	−0.131	−0.135	−0.108	1
11. RMSSD	63.86 ± 24.83	−0.003	−0.006	0.063	−0.044	−0.101	−0.065	−0.046	−0.003	−0.032	0.631**	1
12. pNN50	37.90 ± 16.44	0.000	0.069	0.063	−0.047	−0.062	−0.069	0.044	0.065	0.014	0.504**	0.917**	1
13. LF	1312.82 ± 863.15	0.008	−0.038	0.039	−0.037	−0.215	0.059	−0.016	−0.025	0.035	0.758**	0.673**	0.556**	1
14. HF	1614.01 ± 1320.89	−0.019	0.055	0.029	−0.023	−0.004	−0.075	0.007	0.052	0.025	0.522**	0.923**	0.892**	0.597**	1
15. LF/HF	1.08 ± 0.72	0.048	−0.045	−0.060	−0.026	−0.201	0.072	0.015	−0.052	0.014	0.067	−0.484**	−0.574**	0.200	−0.564**	1

^*p < 0.05,

^**p < 0.01.