Heart rate variation and serum dopamine-beta-hydroxylase activity in workers exposed to vibration

Tests of autonomic nervous function were conducted on 38 workers who had been exposed to vibration [16: VWF(+) group, 22: VWF(-) group, VWF: vibration-induced white finger] and 17 workers who had not been exposed to vibration (control group). Measurements were made of R-R interval variation of the electrocardiogram at rest and during deep breathing, and serum dopamine-beta-hydroxylase (DBH) activity during an immersion test of the hand in 10 degrees C water. Heart-rate variation related to respiratory arrhythmia indicates parasympathetic activity, and serum DBH activity is regarded as an indicator of sympathetic activity. The variations in the R-R interval during deep breathing were smallest in the VWF(+) group, followed by the VWF(-) group (P less than 0.05 and P less than 0.01, compared with the control group). The DBH activity of the VWF(+) group was larger than those of the VWF(-) group and the control group, however, the differences were small and not statistically significant. The reduced R-R interval variations in the VWF(+) and the VWF(-) groups support the hypothesis that autonomic nervous function can be affected by exposure to vibration. The change of DBH activity induced by cold exposure may be an unsuitable index of sympathetic tone. Further study of the autonomic nervous function in workers with vibration syndrome is recommended.