Table 1.
Basic characteristics and sleep parameters of the study participants overall and by electroencephalogram-based sleep cluster.
| Variables | Overall (n = 100) |
(i) Better sleep group (n = 39) |
(ii) Middle sleep group (n = 46) |
(iii) Worse sleep group (n = 15) |
P value comparing the 3 groups |
|---|---|---|---|---|---|
| Age (years), mean ± SD | 44.0 ± 8.6 | 42.0 ± 9.4 | 45.2 ± 8.2 | 45.5 ± 7.0 | 0.1769 |
| Sex (men), n (%) | 50 (50.0) | 13 (33.3) | 27 (58.7) | 10 (66.7) | 0.0248 |
| Body mass index, mean ± SD | 22.2 ± 3.7 | 21.7 ± 3.6 | 22.0 ± 2.9 | 24.0 ± 5.8 | 0.1243 |
| Smoking habit, n (%) | 0.1653 | ||||
| Non-smokers | 75 (75.0) | 34 (87.2) | 32 (69.6) | 9 (60.0) | |
| Past smokers | 14 (14.0) | 2 (5.1)a | 9 (19.6)b | 3 (20.0)c | |
| Current smokers | 11 (11.0) | 3 (7.7) | 5 (10.9) | 3 (20.0) | |
| Drinking habit, n (%) | 0.1238 | ||||
| None | 29 (29.0) | 16 (41.0) | 11 (23.9) | 2 (13.3) | |
| ≤ 1 day/week | 35 (35.0) | 12 (30.8) | 19 (41.3) | 4 (26.7) | |
| 2–5 days/week | 19 (19.0) | 8 (20.5) | 7 (15.2) | 4 (26.7) | |
| ≥ 6 days/week | 17 (17.0) | 3 (7.7) | 9 (19.6) | 5 (33.3) | |
| 3%ODI (times/hour), mean ± SD | 7.3 ± 8.6 | 5.5 ± 7.4 | 7.3 ± 8.3 | 11.9 ± 11.0 | 0.0500 |
| EEG-based parameters, mean ± SD | |||||
| Total sleep time (min) | 348.6 ± 58.4 | 347.6 ± 52.0 | 348.4 ± 58.5 | 352.1 ± 75.6 | 0.9680 |
| Sleep efficiency (%) | 90.8 ± 5.3 | 93.8 ± 3.0 | 90.2 ± 4.3 | 84.7 ± 7.2 | < 0.0001 |
| Sleep latency (min) | 11.2 ± 9.7 | 7.9 ± 6.7 | 12.7 ± 9.9 | 15.4 ± 13.3 | 0.0142 |
| N1% | 8.6 ± 4.8 | 5.7 ± 2.5 | 8.9 ± 3.2 | 15.1 ± 6.6 | < 0.0001 |
| N2% | 54.2 ± 7.1 | 49.2 ± 5.5 | 58.2 ± 5.6 | 55.3 ± 7.4 | < 0.0001 |
| N3% | 10.1 ± 7.7 | 17.0 ± 5.6 | 4.7 ± 3.9 | 8.8 ± 7.4 | < 0.0001 |
| REM% | 26.9 ± 4.9 | 28.0 ± 4.2 | 28.2 ± 4.3 | 20.2 ± 3.0 | < 0.0001 |
| WASO (min) | 24.4 ± 19.3 | 14.9 ± 9.5 | 25.0 ± 16.0 | 47.1 ± 27.6 | < 0.0001 |
| Arousal index (/hour) | 11.8 ± 4.6 | 9.2 ± 3.0 | 11.4 ± 3.1 | 19.5 ± 3.6 | < 0.0001 |
| Sleep stage transitions (/hour) | 7.7 ± 2.2 | 6.9 ± 1.5 | 7.3 ± 1.9 | 10.6 ± 2.2 | < 0.0001 |
EEG electroencephalogram, SD standard deviation, ODI oxygen desaturation index, REM rapid eye movement, WASO wake after sleep onset.
a2 participants quitted smoking ≥ 10 years ago.
b6, 1, 1, and 1 participants quitted smoking ≥ 10, 7–9, 4–6, and 1–3 years ago, respectively.
c2 and 1 participants quitted smoking 4–6 and 1–3 years ago, respectively.