Table 1

Characteristics of the study population

Work (type of exposure)*
Rock face stabilisersGuardrail workersOther low exposure jobs
(Rock drill exp.)(Impact wrench exp.)(Low/no exposure)
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–21770–7
Vibration exposure, min/day‡47150–47
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.