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Demographic characteristics of the study participants (N = 982).
| n (%) | Mean (SD) | |
| Age (year) | 39.8 (11.3) | |
| Gender | ||
| Men | 501 (51.0) | |
| Women | 481 (49.0) | |
| Marriage | ||
| Yes (including co-habitant) | 496 (50.5) | |
| No | 486 (49.5) | |
| Education | ||
| Collage or lower | 488 (49.7) | |
| University or higher | 494 (50.3) | |
| Occupation | ||
| White collar | 817 (83.2) | |
| Blue collar | 165 (16.8) | |
| Shift work | ||
| No | 873 (88.9) | |
| Yes | 109 (11.1) | |
| Working hours/week | 40.3 (18.7) | |
