| Risk group classification | All subjects | |||
| Low risk | Intermediate risk | High risk | ||
| Baseline | ||||
| n | 386 | 537 | 418 | 1341 |
| Mean age (years) (range) | 43 (19–60) | 43 (19–61) | 47 (23–60) | 44 (19–61) |
| Sex (female; %) | 19 | 12 | 6 | 12 |
| Blue-collar (%) | 52 | 58 | 78 | 62 |
| Sickness absence | ||||
| None (% within group) | 46 | 49 | 30 | 42 |
| Mean (days) | 5.6 | 5.3 | 18.8 | 9.6 |
| Standard deviation | 13.9 | 10.6 | 36.6 | 23.6 |
| Median (days) | 1 | 1 | 5 | 2 |
| Upper quartile (days) | 6 | 5 | 19 | 9 |
| Maximum (days) | 145 | 72 | 229 | 229 |
| Sum (days) | 2156 | 2827 | 7854 | 12837 |
| Employment terminated during follow-up (%) | 7 | 6 | 8 | 7 |
| 1 year follow-up | ||||
| n | 358 | 505 | 384 | 1247 |
| Sickness absence | ||||
| None (% within group) | 46 | 45 | 27 | 40 |
| Mean (days) | 6.1 | 6.9 | 24.6 | 12.1 |
| Standard deviation | 13.1 | 13.4 | 49.1 | 30.5 |
| Median (days) | 1 | 1 | 6 | 2 |
| Upper quartile (days) | 6 | 7 | 21 | 10 |
| Maximum (days) | 107 | 115 | 365 | 365 |
| Sum (days) | 2181 | 3506 | 9446 | 15132 |
The risk classification predicted sickness absence: 62% of sickness absence days during the 12-month follow-up took place within the high risk group (table 2).