Table 1.

Descriptive statistics and correlations for HF-HRV_wake and HF-HRV_sleep (whole night) with primary indices of sleep quality.

Variables	M	SD	HF-HRV_wake	HF-HRV_sleep
HF-HRV_wake (ms²)^a	8.17	1.02	−
HF-HRV_sleep (ms²)^a	8.77	0.80	.52^**	−
PSQI (sum score)^b	4.10	1.37	−.39^*	−.32⁺
Sleep latency (min)^b	25.71	19.06	−.43^*	−.17
Total sleep time (min)^b	445.81	22.97	.06	−.17
Sleep efficiency (%)^b	92.86	4.70	.07	−.18
Wake after sleep onset (min)^b	13.50	15.81	.25	.26
Awakenings (N)^a	10.03	6.29	.19	.24
Arousals (N)^a	177.62	67.47	−.53^**	−.03

Note: N = 29.

HF-HRV = high-frequency heart rate variability; PSQI = Pittsburgh Sleep Quality Index, with lower values indicating better sleep quality.

Correlation between: HF-HRV wake & PSQI: p = .039; HF-HRV wake & SL: p = .022; HF-HRV wake & Arousals: p = .003; HF-HRV sleep & PSQI: p = .086.

Pearson correlations.

Spearman rho correlations.

p < .05.

^**

p < .01.

⁺

p < .10.