A longitudinal study of finger systolic blood pressure and exposure to hand-transmitted vibration.

OBJECTIVES

To investigate prospectively the relation between vibration-induced white finger (VWF), exposure to hand-transmitted vibration (HTV) and the cold response of digital arteries in users of vibrating tools.

METHODS

Two-hundred and sixteen HTV workers and 133 control men of the same companies underwent initially a medical examination and a standardised cold test with measurement of the change in finger systolic blood pressure (FSBP) after finger cooling from 30 to 10 degrees C. They were re-examined 1 year later. Tool vibration magnitudes were expressed as frequency-weighted and unweighted r.m.s. accelerations. From the vibration magnitudes and exposure durations, alternative measures of cumulative vibration dose were calculated for each HTV worker, according to the expression: Sigma(alpha)(m)(i)(t)(i), where a ( i ) is the acceleration magnitude on tool i, t ( i ) is the lifetime exposure duration for tool i, and m = 0, 1, 2 or 4.

RESULTS

Among the HTV workers, the initial prevalence and the 1-year incidence of VWF were 18.1 and 1.7%, respectively. At the first examination, the HTV workers with moderate or severe score for VWF showed a significantly increased cold reaction in the fingers when compared with the controls and the HTV workers with no vascular symptoms. At the follow-up, the controls, the asymptomatic HTV workers, and the prevalent cases of VWF did not show significant changes in the cold response of digital arteries. A deterioration of cold-induced digital vasoconstriction was found in the incident cases of VWF. In the HTV workers, vibration doses with high powers of acceleration (i.e., Sigma(alpha)(m)(i)(t)(i) with m > 1) were major predictors of the vasoconstrictor response to cold at the follow-up examination.

CONCLUSIONS

The measurement of FSBP after local cooling may be a helpful objective test to monitor prospectively the change in vibration-induced vascular symptoms. The findings of this longitudinal study suggest a dose-effect relationship between cold-induced digital arterial hyperresponsiveness over time and measures of cumulative vibration exposure. In the controls, the cold response of the digital arteries was stable over 1-year follow-up period.