Table 3.
Heart rate variability characteristics and differences during awake and bedtime period.
| Variable | Mean ± SD | p a | ||
|---|---|---|---|---|
| Total (n = 72) | Low PSQI group (n = 42) | High PSQI group (n = 30) | ||
| Awake period | ||||
| Time domain | ||||
| SDNN (ms) | 123.11 ± 29.71 | 125.09 ± 30.15 | 120.34 ± 29.36 | 0.398 |
| RMSSD (ms) | 36.52 ± 13.08 | 37.17 ± 13.90 | 35.62 ± 12.02 | 0.583 |
| pNN50 (%) | 14.50 ± 9.44 | 14.97 ± 9.69 | 13.85 ± 9.19 | 0.545 |
| Frequency domain | ||||
| LF (ms2) | 971.36 ± 392.77 | 1004.30 ± 407.73 | 925.25 ± 372.69 | 0.253 |
| HF (ms2) | 551.85 ± 449.87 | 554.94 ± 465.32 | 547.52 ± 435.14 | 0.936 |
| LF/HF | 2.39 ± 1.35 | 2.38 ± 1.11 | 2.39 ± 1.65 | 0.530 |
| Bedtime period | ||||
| Time domain | ||||
| SDNN (ms) | 116.21 ± 30.99 | 117.01 ± 29.29 | 115.10 ± 33.69 | 0.553 |
| RMSSD (ms) | 63.86 ± 24.83 | 63.38 ± 22.62 | 64.54 ± 28.03 | 0.950 |
| pNN50 (%) | 37.90 ± 16.44 | 37.22 ± 16.87 | 38.85 ± 16.05 | 0.564 |
| Frequency domain | ||||
| LF (ms2) | 1312.82 ± 863.15 | 1215.85 ± 573.19 | 1448.59 ± 1151.89 | 0.855 |
| HF (ms2) | 1614.01 ± 1320.89 | 1608.75 ± 1392.53 | 1621.3787 ± 1236.93 | 0.623 |
| LF/HF | 1.08 ± 0.72 | 1.03 ± 0.52 | 1.15 ± 0.95 | 0.855 |
a
Comparison between the two groups (non-paried): continuous variable (Mann-Whitney U-test). Low PSQI group indicated that the scores were below 5 and good sleep quality; High PSQI group indicated that the scores were above 5 and poor sleep quality. HRV refers heart rate variability. Mean values (± SD) for the indices of each group.