The distribution of characteristics among the study population
| Variables | Exposed (n=53) | Comparison (n=121) | p Value |
| Age (y, mean (SD)) | 29.89 (7.25) | 29.58 (7.55) | 0.86 |
| Duration of employment (y, mean (SD)) | 2.60 (2.90) | 3.58 (2.82) | 0.03 |
| Body mass index (kg/m2, mean (SD)) | 23.81 (5.31) | 22.45 (3.41) | 0.04 |
| Sex (male, n (%)) | 47 (88.7) | 93 (76.0) | 0.03 |
| Marital status (single, n (%)) | 23 (43.4) | 58 (47.9) | 0.36 |
| Smoking status (smoker, n(%)) | 32 (60.4) | 80 (66.1) | 0.50 |