| CRSD | Circadian rhythm sleep disorder |
| HF | High frequency |
| HRV | Heart rate variability |
| N.R. | Not reported |
| OBS | Observational study |
| PSQI | Pittsburgh Sleep Quality Index |
| REM | Rapid eye movement |
| RMSSD | Root Mean Square of Successive Differences between Normal Heartbeats |
| RTC | Randomized controlled trial |
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