Table 2.
Mean (SD) heart rate variability values according to sleep stages and sleep cycle.
| Cycle onset time | Sleep stage and sleep cycle | Heart rate variability | |||||
|---|---|---|---|---|---|---|---|
| Time domain variables | Power domain variables | ||||||
| Mean NN | SDNN | rMSSD | LF_FFT | HF_FFT | LF:HF | ||
| 21:40 | Pre-sleep | 704.6 (9.4) | 55.9 (3.7) | 48.1 (4.6) | 1440.8 (388.0) | 944.6 (139.6) | 1.83 (0.24) |
| 22:58 | SWS1 | 775.7 (10.3) | 56.1 (4.1) | 68.8 (5.5) | 639.4 (94.7) | 1768.5 (294.9) | 0.68 (0.09) |
| 24:44 | SWS2 | 809.4 (11.5) | 57.9 (4.0) | 70.8 (5.9) | 750.3 (91.5) | 1974.8 (346.0) | 0.69 (0.07) |
| 01:39 | REM3 | 754.7 (11.1) | 62.6 (4.3) | 61.8 (5.9) | 937.3 (170.8) | 1483.1 (364.5) | 1.16 (0.12) |
| 02:40 | SWS3 | 824.6 (13.0) | 59.7 (4.5) | 71.5 (6.7) | 922.3 (148.9) | 2059.8 (370.1) | 1.06 (0.20) |
| 03:26 | REM2 | 772.9 (11.2) | 71.6 (5.2) | 74.0 (7.3) | 1501.2 (243.2) | 2299.4 (264.6) | 1.82 (0.30) |
| 05:01 | REM1 | 763.7 (10.4) | 68.2 (4.3) | 67.1 (5.9) | 1316.7 (235.4) | 2020.5 (377.1) | 1.91 (0.26) |
Note: Although Stage 3 and 4 are combined for reporting purposes, we restricted our SWS analysis to Stage 4 sleep (Standard Deviation).
SWS, slow wave sleep. SWS cycles are labeled relative to sleep onset: SWS cycle after sleep onset = 1st SWS, SWS cycle after sleep onset but one = 2nd SWS and SWS cycle after sleep onset but two = 3rd SWS cycle. REM, rapid eye movement sleep. REM cycles are labeled relative to sleep offset: REM cycle prior to sleep offset = REM1, REM cycle preceding sleep offset but one = REM2 and REM cycle preceding sleep offset but two = REM3 (see Figure 1).