Characteristics of the study population
| Work (type of exposure)* | |||
| Rock face stabilisers | Guardrail workers | Other low exposure jobs | |
| (Rock drill exp.) | (Impact wrench exp.) | (Low/no exposure) | |
| n | 51 | 46 | 51 |
| Age, years, mean (SD) | 35.6 (10.7) | 43.5 (10.6) | 39 (15.2) |
| Body mass index, kg m–2, mean (SD) | 25.8 (2.8) | 28.9 (4.4) | 27.4 (3.6) |
| Smoking or tobacco snuffing, n (%)† | 28 (55) | 28 (61) | 26 (51) |
| Vibration exposure level, ms–2‡ | 17 | 7 | 0–7 |
| Vibration exposure, min/day‡ | 47 | 15 | 0–47 |
| Vibration exposure, hours ms–2, mean (SD)§ | 14 140 (19 713) | 2982 (3514) | 1218 (1753) |
| Vibration exposure, years, mean (SD) | 8.3 (10.2) | 11.8 (11.3) | 11.9 (13.3) |
| Increased exposure during follow-up, n (%)¶ | 2 (8) | 1 (5) | 0 |
| Decreased exposure during follow-up, n (%)¶ | 9 (45) | 2 (10) | 0 |
| Finger/hand injuries, n (%)** | 6 (11) | 4 (21) | 6 (11) |
| Hand function, n (%)†† | 4 (8) | 11 (24) | 3 (6) |
| White fingers, n (%)†† | 14 (27) | 5 (11) | 1 (2) |
| Finger numbness, n (%)†† | 23 (45) | 15 (35) | 4 (8) |
| Finger tingling, n (%)†† | 27 (53) | 14 (30) | 8 (16) |
*n=3 subjects in the impact wrench group had in previous work also been exposed to rock drills. One subject in the impact wrench group was unexposed the last 6 years.
†n=3 subjects quit using tobacco during the follow-up period.
‡Estimates of average exposure level and exposure time are based on repeated measurements of typical work processes. Twenty-five workers in the low/no exposure jobs had exposure from impact wrenches, rock drills, mainly from previous work.
§Average cumulative baseline exposure based on measured average exposure from main tool multiplied by lifetime hours of exposure.
¶Subjects were asked about whether they had experienced any notable change in vibration exposure at work during the 4-year follow-up period.
**Finger/hand injuries were injuries which made it impossible to measure vibration perception thresholds (such as missing fingers).
††Subjects were asked about symptoms as well as hand functioning in activities of daily life.