Table 1.

Autonomic functions in different sleep stages

HRV	Wakefulness	Stage 2	REM	Significance
TF	6.5 ± 6.2	6.3 ± 5.8	11.2 ± 10.2	0.001
LF	2.0 ± 2.8	2.1 ± 2.6	2.7 ± 3.0	0.013
HF	1.2 ± 1.5	1.7 ± 2.4	1.3 ± 2.7	0.012
LF/HF	2.7 ± 2.6	2.0 ± 2.2	3.9 ± 3.6	0.001

HF, high frequency; HRV, heart rate variable; LF, low frequency; REM, rapid eye movement; TF, total frequency.