TABLE 3.

Heart rate variability in frequency band 0 – 0.15 Hz $\frac{{(seconds RMS)}^{2}}{H z}$ during Hz sleep stages (mean ± SE)

Stage	Mean	N	SE
Awake^a	1.41	47	0.16
Stage 1^b	1.34	17	0.22
Stage 2^a	0.89	10	0.11
Stages 3, 4^a,^b	0.31	9	0.30
REM	1.06	6	0.35

Significantly different from each other, P < 0.02, planned comparison with Bonferroni correction for degrees-of-freedom.

Significantly different from each other, P < 0.05, planned comparison with Bonferroni correction for degrees-of-freedom.

N = number of observations.