A follow up study of vascular disorders in vibration-exposed forestry workers.

OBJECTIVES: To investigate the occurrence of vibration-induced white finger (VWF) and the cold response of digital arteries in a group of forestry workers, most of whom had used anti-vibration (AV) chain saws solely.
METHODS: One hundred and twenty-eight forestry workers underwent initially a medical examination and a standardized cold test with measurement of the change in finger systolic blood pressure after finger cooling from 30 to 10 degrees C (FSBP%(10 degrees )). They were re-examined two or three times over the calendar period 1990-1999. Seventy-one forestry workers were active over the entire follow up period, while 57 retired after 1-8 years from the initial investigation.
RESULTS: The initial prevalence and the cumulative incidence of VWF over the follow up period were 26.6 and 11.7%, respectively. In the retired workers, the new cases of VWF occurred before their retirement, that is when they were still active. There were no significant changes in FSBP%(10 degrees ) in the active forestry workers over the follow up period. A significant increased in FSBP%(10 degrees ) (i.e. improvement) was observed in the retired workers at the end of the follow up. FSBP%(10 degrees ) at the cross-sectional investigation was significantly lower in the forestry workers who developed VWF during the follow up than in those who never experienced finger blanching over the study period.
CONCLUSION: The findings of this follow up study suggest that forestry workers with work experience limited to AV chain saws are still at risk of developing VWF. Cessation of vibration exposure in the retired workers was associated with a beneficial effect on the cold response of digital arteries. Cold-induced digital arterial hyperresponsiveness at the initial investigation was a predictive factor for the onset of VWF over time.