Distribution of potential confounders across levels of cumulated exposure
| Cumulated angular velocity | Level 1*(lowest) | Level 2* | Level 3* | Level 4* | Level 5* (highest) | Total |
| Person years | 4 051 052 | 4 054 683 | 4 052 995 | 4 044 577 | 4 032 033 | 20 235 440 |
| Men, % | 47.9 | 50.8 | 51.7 | 53.4 | 66.2 | 53.4 |
| Women, % | 52.1 | 49.2 | 48.3 | 46.6 | 33.8 | 46.6 |
| Mean age (IQR) | 31.8 (24.4–37.3) | 36.6 (29.8–41.8) | 41.4 (35.2–46.7) | 46.9 (40.2–53.3) | 51.2 (44.5–58.0) | 41.6 (32.7–49.9) |
| Lumbar disc herniation, cases | 5672 | 8112 | 9659 | 10 323 | 10 436 | 44 202 |
| Men, % | 49.5 | 53.4 | 53.8 | 54.8 | 68.2 | 56.8 |
| Women, % | 50.5 | 46.6 | 46.2 | 45.2 | 31.8 | 43.2 |
| Lumbar disc herniation, IR | 14.0 | 20.0 | 23.8 | 25.5 | 25.9 | 21.8 |
Shown for angular velocity.
*Based on quintiles of cumulative exposure in the study population.
IR, incidence rate.