Table 1. Characteristics of the study participants by work schedule.
| Regular work | Shift work without | Shift work with | Only night | P value | |
|---|---|---|---|---|---|
| (N = 3660) | night work | night work | work | ||
| (N = 181) | (N = 1276) | (N = 142) | |||
| Age (years) | 41.9 (10.4) | 37.4 (11.3) | 35.4 (12.1) | 43.2 (8.8) | < 0.001 |
| Sex (male, %) | 69.1 | 87.8 | 92.0 | 39.4 | < 0.001 |
| Height (cm) | 167.1 (8.2) | 169.5 (7.5) | 170.0 (6.7) | 162.6 (7.3) | < 0.001 |
| Weight (kg) | 64.74 (12.7) | 66. (11.8) | 66.72 (11.9) | 59. (12.1) | < 0.001 |
| BMI (Kg/m2) | 23.1 (3.6) | 23.2 (3.5) | 23.0 (3.6) | 22.6 (4.0) | 0.446 |
| Lifestyle | |||||
| Smoking status | |||||
| Never (%) | 60.4 | 53.3 | 48.4 | 50.7 | < 0.001 |
| Former (%) | 11.2 | 9.4 | 12.8 | 11.3 | |
| Current (%) | 28.4 | 37.2 | 38.9 0 | 38.0 | |
| Frequency of alcohol drinking | |||||
| None (%) | 37.7 | 41.1 | 40.2 | 52.1 | < 0.001 |
| Sometimes (%) | 33.7 | 34.4 | 38.7 | 31.7 | |
| Every day (%) | 28.6 | 24.4 | 21.1 | 16.2 | |
| Physical exercise (%) | |||||
| None (%) | 64.7 | 66.3 | 68.9 | 71.9 | 0.207 |
| Light exercise more than once a week (%) | 21.5 | 21.3 | 18.2 | 17.3 | |
| Heavy exercise once or twice a week (%) | 10.9 | 10.1 | 10.5 | 7.2 | |
| Heavy exercise more than three times a week (%) | 2.9 | 2.2 | 2.4 | 3.6 | |
| Socioeconomic status | |||||
| Years of education 12 or less (%) | 48.9 | 63.4 | 71.3 | 81.6 | < 0.001 |
| Hours worked per week | |||||
| Less than 40 (%) | 43.2 | 35.5 | 43.5 | 91.6 | < 0.001 |
| 41–60 (%) | 50.8 | 57.4 | 9.3 | 7.0 | |
| 60 or more (%) | 6.0 | 13.1 | 47.2 | 1.4 | |
| Household income (million JPY/year) | |||||
| Less than 2.99 (%) | 9.3 | 7.9 | 9.8 | 38.3 | < 0.001 |
| 3.00–7.99 (%) | 55.1 | 179.7 | 69.7 | 45.4 | |
| More than 8.00 (%) | 35.6 | 12.4 | 20.6 | 16.3 | |
| Illness history | |||||
| Dyslipidemia (%) | 41.4 | 37.6 | 39.9 | 36.6 | 0.41 |
| Diabetes mellitus (%) | 8.6 | 4.4 | 8.1 | 4.9 | 0.107 |
| Hypertension (%) | 15.9 | 12.7 | 14.3 | 12.7 | 0.298 |
| Laboratory data | |||||
| TG (mg/dL) | 99.0 [66.0, 157.0] | 102.0 [68.0, 152.0] | 105.0 [67.0, 163.0] | 91.5 [64.3, 126.5] | 0.119 |
| LDL-C (mg/dL) | 117.5 (30.5) | 112.3 (28.4) | 112.3 (30.6) | 117.4 (30.5) | < 0.001 |
| HDL-C (mg/dL) | 62.6 (16.1) | 61.4 (16.5) | 59.6 (15.0) | 65.4 (15.6) | < 0.001 |
| HbA1c (%, NGSP) | 5.0 [4.8, 5.2] | 4.9 [4.8, 5.1] | 5.0 [4.8, 5.2] | 5.0 [4.8, 5.2] | < 0.001 |
| Hs-CRP (mg/L) | 0.26 [0.12, 0.62] | 0.22 [0.11, 0.45] | 0.26 [0.12, 0.60] | 0.22 [0.11, 0.48] | 0.13 |
| IL-6 (pg/mL) | 1.40 [0.90, 2.10] | 1.60 [1.00, 2.10] | 1.50 [0.90, 2.10] | 1.70 [1.20, 2.50] | < 0.001 |
| Job stress | |||||
| Effort–Reward Balance | 0.44 (0.15) | 0.50 (0.16) | 0.44 (0.14) | 0.41 (0.15) | < 0.001 |
Note: Data are expressed as mean and standard deviation, or as median with 25th and 75th percentiles, or percentages.
Abbreviations: BMI, body mass index; Hs-CRP, high sensibility C-reactive protein; HDL-C, high-density lipoprotein cholesterol; LDL-C, low-density lipoprotein cholesterol; Log (Hs-CRP), log-transformed Hs-CRP; Log (IL-6), log-transformed IL-6; NGSP, National Glycohemoglobin Standardization Program; TG, triglyceride.