Table 1.
Study participant characteristics by sleep–wake regularity (ISsw)
| Lower half of ISsw | Upper half of ISsw | All | |
|---|---|---|---|
| Subjects | 21 | 21 | 42 |
| ISsw | 61.9 (12.1) | 81.4 (4.8) | 71.6 (13.4) |
| Demographics | |||
| Age (years) | 22.2 (2.8) | 23.2 (2.6) | 22.7 (2.7) |
| Female | 52.4% (11) | 52.4% (11) | 52.4% (22) |
| Caucasian | 47.6% (10) | 38.1% (8) | 42.9% (18) |
| Asian | 38.1% (8) | 52.4% (11) | 45.2% (19) |
| Black/African American | 14.3% (3) | 9.5% (2) | 11.9% (5) |
| Baseline vital signs | |||
| HR (bpm) | 69.5 (11.6) | 70.2 (10.6) | 69.8 (11.0) |
| BP (mmHg) | 117/68 (13/10) | 116/67 (10/8) | 116/68 (12/9) |
| BMI (kg/m2) | 24.1 (3.1) | 23.3 (3.9) | 23.7 (3.5) |
| RR (breaths/min) | 17.3 (3.1) | 17.8 (2.4) | 17.6 (2.8) |
| Sleep and activity measures | |||
| Chronotype (MEQ score)—baseline | 45.8 (7.0) | 52.0 (7.3) | 48.9 (7.7) |
| Sleep duration (hr/night) | 7.8 (0.7) | 7.6 (0.8) | 7.7 (0.7) |
| Delayed bedtime (hr/week) | 10.7 (8.5) | 5.0 (6.4) | 7.8 (8.0) |
| Social jetlag (min) | 53.0 (99.4) | 26.9 (51.3) | 40.6 (80.4) |
| Physical activity (MET-min/week)† | 8.0 (0.6) | 7.8 (0.9) | 7.9 (0.7) |
| Mood | |||
| BDI—during study | 6.2 (5.1) | 2.1 (2.6) | 4.2 (4.5) |
| ΔBDI—weekly change | 1.4 (2.7) | −0.2 (1.6) | 0.6 (2.3) |
| Hear rate variability (during study) | |||
| Heart rate (sleep) | 65.3 (10.1) | 62.6 (6.6) | 63.9 (8.5) |
| Heart rate (wake) | 79.5 (7.7) | 83.1 (7.9) | 81.3 (7.9) |
| High-frequency power (sleep)† | 2.91 (0.42) | 3.12 (0.25) | 3.02 (0.36) |
| High-frequency power (wake)† | 2.63 (0.34) | 2.60 (0.25) | 2.62 (0.29) |
Data for 42 participants. Mean (standard deviation) and percentages (number of subjects). Lower half (1st and 2nd quartiles), upper half (3rd and 4th quartiles) for mean participant ISsw across the study.
ISsw = interdaily stability of sleep–wake times; HR = heart rate; bpm = beats per minute; BP = blood pressure; mmHg = millimeters mercury; BMI = body mass index; RR = respiratory rate; MEQ = morning–eveningness questionnaire; min = minutes; MET-min = Metabolic Equivalent of Task x minutes product; BDI = Beck Depression Inventory; ΔBDI = change in BDI.
†log-transformed.