Table 3. Results of paired t-tests or Wilcoxon signed-rank tests of the behavioral rhythm and sleep parameters between Night 1 and Night 2.
| Type of sample | Variables | Night 1 | Night 2 | t or Z | df | p-value (two tailed) |
|---|---|---|---|---|---|---|
| Mean ± SD | Mean ± SD | |||||
| Behavioral rhythm (n = 25) | Period (hr) | 24.064 ± 0.617 | 23.900 ± 0.585 | 1.071 | 24 | 0.295 |
| Amplitude | 168.331 ± 53.029 | 184.816 ± 53.643 | −1.085 | 24 | 0.289 | |
| Acrophase (time) | 15.649 ± 1.714 | 15.332 ± 1.436 | 0.662 | 24 | 0.515 | |
| Mesor | 243.126 ± 71.803 | 244.961 ± 59.853 | −0.098 | 24 | 0.923 | |
| Robustness (%) | 24.008 ± 7.854 | 23.476 ± 5.277 | 0.301 | 24 | 0.766 | |
| Sleep parameters (n = 21) | TST (min)* | 384.380 ± 18.202 | 385.548 ± 16.381 | −0.818 | — | 0.413 |
| SE (%) | 97.433 ± 1.580 | 97.405 ± 1.775 | 0.099 | 20 | 0.922 | |
| WASO (min)* | 6.024 ± 5.278 | 5.74 ± 5.449 | −1.252 | — | 0.211 | |
| SL (min) | 4.000 ± 2.617 | 4.520 ± 3.120 | −0.732 | 20 | 0.473 | |
| Stage N1 (%) | 12.262 ± 4.923 | 13.395 ± 6.688 | −1.213 | 20 | 0.239 | |
| Stage N2 (%) | 45.267 ± 5.791 | 44.467 ± 5.865 | 0.535 | 20 | 0.598 | |
| Stage N3 (%) | 18.638 ± 7.386 | 17.557 ± 8.642 | 0.994 | 20 | 0.332 | |
| Stage R (%) | 23.848 ± 4.777 | 24.571 ± 3.761 | −0.818 | 20 | 0.423 | |
| Stage R latency (min)* | 71.430 ± 42.432 | 71.762 ± 40.937 | −0.709 | — | 0.478 | |
| RDI* | 4.067 ± 2.923 | 4.090 ± 3.470 | −0.348 | — | 0.728 | |
| AHI | 2.433 ± 0.382 | 2.400 ± 2.399 | 0.117 | 20 | 0.908 | |
| RERAI | 1.633 ± 1.451 | 1.720 ± 1.591 | −0.633 | 20 | 0.534 | |
| PLMI* | 2.150 ± 5.899 | 2.929 ± 8.166 | −0.691 | — | 0.490 | |
| LMI* | 5.676 ± 6.419 | 6.933 ± 9,168 | −0.869 | — | 0.385 | |
| TA (min) | 12.952 ± 4.249 | 13.410 ± 5.311 | −0.718 | 20 | 0.481 | |
| SA (min) | 8.052 ± 3.800 | 8.424 ± 4.537 | −0.688 | 20 | 0.499 | |
| Supine position (%)* | 77.790 ± 18.453 | 80.252 ± 20.704 | −0.262 | — | 0.793 |
†p-value < 0.05.
*Wilcoxon signed-rank test.
Night 1, exposure to artificial light of 150-lux intensity at night.
Night 2, exposure to artificial light of 1,000-lux intensity at night.
All variables except those tested using the Wilcoxon signed-rank test were analyzed by a paired t-test.
hr, hour; time, time of the day; TST, total sleep time; SE, sleep efficiency; WASO, wake time after sleep onset; SL, sleep latency; AHI, apnea + hypopnea index; RDI, respiratory disturbance index; RERAI, respiratory effort-related arousal index; PLMI, periodic limb movement during sleep index; LMI, limb movement index; TA, total arousal; SA, spontaneous arousal; min, minutes; n, number of subjects; SD, standard deviation; and df, degrees of freedom.