Table 3.

Characteristics of heart rate variability of RR interval in normal subjects and patients with sleep apnea-hypopnea syndrome across first three NREM-REM cycles

Normal ControlModerate-to-Severe SAHSSevere SAHS
Heart rate variabilities of RRI
TF, ms22,945.38 (2,003.55)3,056.27 (1,897.29)3,360.21 (2,178.15)
LF, ms21,121.59 (606.26)1,156.65 (848.03)1,127.52 (720.26)
HF, ms2392.10 (331.74)478.62 (367.54)552.70 (622.95)
LF-to-HF ratio3.89 (2.25)3.19 (2.74)2.78 (1.59)
LFnu75.86 (9.78)68.76 (14.10)69.19 (11.83)
HFnu24.14 (9.78)31.24 (14.10)30.81 (11.83)
Heart rate variabilities of RRI across sleep stages
NREM RRI, s1.02 (0.15)0.93 (0.11)0.95 (0.09)
REM RRI, s0.98 (0.13)0.92 (0.13)0.94 (0.12)
Awake RRI, s0.98 (0.13)0.89 (0.10)0.88 (0.07)
NREM LF-to-HF ratio4.15 (2.22)3.18 (2.69)4.07 (2.04)
REM LF-to-HF ratio6.44 (2.96)4.65 (3.15)5.04 (2.56)
Awake LF-to-HF ratio6.25 (2.82)4.82 (2.85)*5.83 (2.95)
NREM LFnu65.59 (11.29)60.61 (11.39)66.23 (13.74)
REM LFnu77.64 (9.84)70.90 (11.09)71.27 (12.23)
Awake LFnu75.63 (8.63)70.05 (11.28)74.18 (11.51)
NREM HFnu34.41 (11.29)39.39 (11.38)33.77 (13.74)
REM HFnu22.36 (9.84)29.10 (11.09)28.73 (12.23)
Awake HFnu24.37 (8.63)29.95 (11.28)25.82 (11.51)
  • Values are means (SD). Comparisons were performed with normal control subjects. TF, total frequency; LF, low frequency; HF, high frequency; LFnu, normalized LF; HFnu, normalized HF. For comparisons of heart rate variability of RR interval across sleep stages,

  • * P < 0.05,

  • P < 0.01,

  • P < 0.001 vs. NREM sleep.