Characteristics of the risk cohort at start of the follow-up period for each individual according to cumulative load lifted within the preceding 5 years.
| Cumulative load lifted in a 5-year period expressed in ton-years* | ||||||||
|---|---|---|---|---|---|---|---|---|
| 0 ton-years | >0–1 ton-year | >1–2 ton-years | >2–3 ton-years | >3–4 ton-years | >4–17.5 ton-years | Missing | n Total | |
| n At start of follow-up, (% of total) | 346 073 (22.4) | 303 650 (19.6) | 244 091 (15.8) | 196 789 (12.7) | 121 032 (7.8) | 322 273 (20.9) | 12 079 (0.8) | 1 545 987 (100) |
| Age at start of follow-up, (years), mean, (SD) | 39.1 (11.8) | 31.2 (12.4) | 34.9 (12.5) | 37.0 (11.9) | 36.5 (12.2) | 39.4 (11.1) | 31.9 (12.5) | 36.4 (12.4) |
| Socioeconomic status in 2003, % | ||||||||
| Self-employed | 4.2 | 5.5 | 6.2 | 8.7 | 6.7 | 13.6 | 2.6 | 7.5 |
| Top managers and employees at upper level | 34.0 | 14.5 | 6.9 | 4.2 | 3.4 | 2.0 | 0.0 | 12.8 |
| Employees at intermediate level | 30.1 | 37.7 | 43.9 | 45.8 | 44.4 | 38.8 | 0.0 | 38.5 |
| Employees at basic level | 10.6 | 14.2 | 19.6 | 21.0 | 23.6 | 28.2 | 44.4 | 19.0 |
| Outside labour market or unemployed | 19.0 | 26.5 | 21.7 | 18.6 | 20.3 | 15.7 | 45.8 | 20.5 |
| Missing | 2.1 | 1.5 | 1.7 | 1.7 | 1.7 | 1.6 | 7.1 | 1.8 |
| Standing-years, % | ||||||||
| 0 | 99.7 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 22.3 |
| >0–2 | 0.2 | 85.1 | 38.3 | 21.9 | 24.1 | 10.1 | 0.0 | 29.6 |
| >2–3 | 0.0 | 11.0 | 19.6 | 11.8 | 17.7 | 12.1 | 0.0 | 10.7 |
| >3–4 | 0.0 | 3.4 | 18.6 | 16.5 | 14.7 | 16.2 | 0.0 | 10.2 |
| >4–5 | 0.0 | 0.5 | 17.2 | 26.3 | 21.4 | 46.0 | 0.0 | 17.4 |
| >5–6.1 | 0.1 | 0.0 | 6.4 | 23.6 | 22.1 | 15.6 | 0.0 | 9.0 |
| Missing | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 100.0 | 0.8 |
| Frequent-heavy-lifting-years, % | ||||||||
| 0 | 100.0 | 1.8 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 22.8 |
| >0–10 | 0.0 | 90.5 | 15.4 | 0.1 | 0.3 | 0.0 | 0.0 | 20.2 |
| >10–20 | 0.0 | 7.7 | 64.1 | 29.2 | 2.2 | 0.0 | 0.0 | 15.5 |
| >20–30 | 0.0 | 0.0 | 13.7 | 39.1 | 25.5 | 1.6 | 0.0 | 9.5 |
| >30–40 | 0.0 | 0.0 | 6.8 | 24.9 | 47.7 | 12.1 | 0.0 | 10.5 |
| >40–48 | 0.0 | 0.0 | 0.0 | 6.7 | 24.3 | 86.3 | 0.0 | 20.7 |
| Missing | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 100.0 | 0.8 |
*One ton-year was defined as lifting one ton per day for 1 year—for example, the number of ton-years would be calculated in the following way for a person with a full-time job (37 h/week) for 1 year lifting 5 tons per day, a full-time job for 2 years lifting 5 tons per day, and a part-time job (30 h/week) for 2 years lifting 8 tons per day: 1×1 year×0.5 ton+1×2 years×5 tons+0.75×2 years×8 tons)=22.5 ton-years.