Table 1.
General characteristics of the subjects.
| Characteristics | Shift Work Schedule | All Subjects N = 352 |
p-Value | |||
|---|---|---|---|---|---|---|
| 3-Day Cycle N = 71 |
6-Day Cycle N = 77 |
9-Day Cycle N = 83 |
21-Day Cycle N = 121 |
|||
| Age (years) | 0.043 3–6 | |||||
| 20–29 | 4 (5.6%) | 11 (14.3%) | 11 (13.3%) | 14 (11.6%) | 40 (11.4%) | |
| 30–39 | 21 (29.6%) | 35 (45.5%) | 29 (34.9%) | 47 (38.8%) | 132 (37.5%) | |
| 40–49 | 30 (42.3%) | 19 (24.7%) | 24 (28.9%) | 48 (39.7%) | 121 (34.4%) | |
| 50–59 | 16 (22.5%) | 12 (15.6%) | 19 (22.9%) | 12 (9.9%) | 59 (16.8%) | |
| Mean ± SD | 42.5 ± 8.1 | 38.4 ± 9.3 | 41.2 ± 9.0 | 39.1 ± 8.0 | 40.1 ± 8.7 | 0.012 3–6,3–21 |
| Sex | 0.051 | |||||
| Men | 61 (85.9%) | 73 (94.8%) | 80 (96.4%) | 114 (94.2%) | 328 (93.2%) | |
| Women | 10 (14.1%) | 4 (5.2%) | 3 (3.6%) | 7 (5.8%) | 24 (6.8%) | |
| Job | 0.009 3–21,6–21 | |||||
| Fire suppression | 14 (19.7%) | 21 (27.3%) | 25 (30.1%) | 51 (42.1%) | 111 (31.5%) | |
| Others | 57 (80.3%) | 56 (72.7%) | 58 (69.9%) | 70 (57.9%) | 241 (68.5%) | |
| Education | 0.046 3–6,6–21 | |||||
| High school | 10 (14.1%) | 24 (31.2%) | 18 (21.7%) | 18 (14.9%) | 70 (19.9%) | |
| 2-year degree | 23 (32.4%) | 23 (29.9%) | 18 (21.7%) | 36 (29.7%) | 100 (28.4%) | |
| 4-year degree | 38 (53.5%) | 30 (39.0%) | 47 (56.6%) | 67 (55.4%) | 182 (51.7%) | |
| Monthly income | <0.001 3–6,3–21,6–9,9–21 | |||||
| Missing | 0 | 0 | 2 | 0 | 2 | |
| Low | 11 (15.5%) | 33 (42.9%) | 12 (14.8%) | 37 (30.6%) | 93 (26.6%) | |
| Middle | 32 (45.1%) | 32 (41.6%) | 42 (51.9%) | 62 (51.2%) | 168 (48.0%) | |
| High | 28 (39.4%) | 12 (15.6%) | 27 (33.3%) | 22 (18.2%) | 89 (25.4%) | |
| Smoking | 0.576 | |||||
| Missing | 0 | 0 | 0 | 1 | 1 | |
| Never | 29 (40.8%) | 37 (48.0%) | 33 (39.8%) | 40 (33.3%) | 139 (39.6%) | |
| Past smoker | 24 (33.8%) | 22 (28.6%) | 21 (25.3%) | 45 (37.5%) | 112 (31.9%) | |
| Current light smoker | 10 (14.1%) | 10 (13.0%) | 17 (20.5%) | 21 (17.5%) | 58 (16.5%) | |
| Current heavy smoker | 8 (11.3%) | 8 (10.4%) | 12 (14.5%) | 14 (11.7%) | 42 (12.0%) | |
| Alcohol | 0.996 | |||||
| Missing | 2 | 3 | 1 | 2 | 8 | |
| No | 15 (21.7%) | 17 (23.0%) | 16 (19.5%) | 24 (20.2%) | 72 (20.9%) | |
| Normal drinking | 41 (59.4%) | 41 (55.4%) | 48 (58.5%) | 69 (58.0%) | 199 (57.9%) | |
| Heavy drinking | 13 (18.8%) | 16 (21.6%) | 18 (22.0%) | 26 (21.8%) | 73 (21.2%) | |
| Regular exercise | 0.636 | |||||
| No | 33 (46.5%) | 36 (46.8%) | 44 (53.0%) | 53 (43.8%) | 166 (47.2%) | |
| Yes | 38 (53.5%) | 41 (53.2%) | 39 (47.0%) | 68 (56.2%) | 186 (52.8%) | |
| Caffeine | 0.045 3–6,3–9 | |||||
| Missing | 5 | 7 | 2 | 4 | 18 | |
| No | 8 (12.1%) | 16 (22.9%) | 15 (18.5%) | 18 (15.4%) | 57 (17.1%) | |
| Light coffee drinking | 25 (37.9%) | 35 (50.0%) | 45 (55.6%) | 61 (52.1%) | 166 (49.7%) | |
| Moderate to heavy coffee drinking | 33 (50.0%) | 19 (27.1%) | 21 (25.9%) | 38 (32.5%) | 111 (33.2%) | |
| Insomnia | 0.148 | |||||
| Normal (≤ 7) | 43 (60.6%) | 31 (40.3%) | 44 (53.0%) | 68 (56.2%) | 186 (52.8%) | |
| Mild Insomnia (8–14) | 21 (29.6%) | 40 (51.9%) | 32 (38.6%) | 41 (33.9%) | 134 (38.1%) | |
| Insomnia (≥ 15) | 7 (9.9%) | 6 (7.8%) | 7 (8.4%) | 12 (9.9%) | 32 (9.1%) | |
| Mean ± SD | 7.3 ± 2.2 | 8.8 ± 2.4 | 7.7 ± 4.7 | 7.2 ± 5.3 | 7.7 ± 5.0 | 0.151 |
| Depression | 0.896 | |||||
| Normal (≤ 4) | 60 (84.5%) | 64 (83.1%) | 71 (85.5%) | 103 (85.1%) | 298 (84.7%) | |
| Mild depression (5–9) | 9 (12.7%) | 9 (11.7%) | 11 (13.3%) | 14 (11.6%) | 43 (12.2%) | |
| Depression (≥ 10) | 2 (2.8%) | 4 (5.2%) | 1 (1.2%) | 4 (3.3%) | 11 (3.1%) | |
| Mean ± SD | 2.2 ± 2.8 | 2.4 ± 3.1 | 2.1 ± 2.3 | 2.0 ± 2.9 | 2.1 ± 2.8 | 0.771 |
Values are presented as means ± standard deviation (SD) or number (%). Analyzed by ANOVA or chi-square test. Types of shift work with significant differences in multiple comparisons are listed with a superscript (3: 3-day cycle, 6: 6-day cycle, 9: 9-day cycle, 21: 21-day cycle). Heavy smoker: smoking of ≥15 cigarettes per day. Heavy drinking: consumption of ≥7 glasses per day at least two times per week in men, ≥5 glasses per day at least two times per week in women. Moderate to heavy coffee drinking: consumption of ≥3 cups per day (moderate: 3–4 cups, heavy: ≥5 cups). Regular exercise: exercise above moderate intensity for more than 1 hour a week.