Vibration exposure and disease in a shipyard: A 13-year revisit

Background: In a 1988 study of shipyard workers, a progressive association was observed between cumulative exposure to vibration and the vascular and neurological symptoms of the hand-arm vibration syndrome (HAVS). In 2001, after a decade of exposure reduction and ageing of the workforce, a second study at the same site was initiated. Methods: In 2001, 214 subjects were selected; they represented four current weekly vibration exposure time intervals-0 hr, >0 < 5 hr, ≥5 < 20 hr, ≥20 hr. The 1988 and 2000 cross-sectional populations were compared on the basis of exposure duration and current symptoms. Results: In 2001, the study population was 9.6 years older than the 1988 group. Current weekly exposure hours were similar in the low and medium exposure groups 2001 and 1988, but exposure was reduced by an average of 9.7 hr per week in the highest exposure group (≥20 hr) in 2001. Symptom severity was regressed polychotomously on estimated exposure (log cumulative hours); the OR was weaker in 2001 than in 1988 for sensorineural symptoms-1.44 [CI 1.04-1.98] versus 2.35 [CI 1.48-3. 73]. This was also true for vascular symptoms-1.70 [CI 1.06-2.71] versus 3.99 [CI 2.27-7.01]. Vascular symptoms were more prevalent in the highest lifetime vibration exposure group in 1988 (68.7 vs. 43.2% in 2001); sensorineural symptoms were more prevalent in the least vibration exposed group in 2001 (52.6 vs. 20.7% in 1988). Conclusions: The prevalence of vascular symptoms associated with cumulative vibratory exposure was significantly greater in 1988, but neurological symptoms were more common at lower exposure levels in 2001. The presumption that reducing exposure duration alone is sufficient, in the absence of change in vibration magnitude, is not supported by the results: of this study.