Autonomic and peripheral nervous system dysfunction in workers exposed to hand-arm vibration: a study of R-R interval variability and distribution of nerve conduction velocities

To assess the effects of vibrating-tool operation on the autonomic and peripheral nervous system, we measured the variability in the electrocardiographic R-R interval (CVRR) and the distribution of nerve conduction velocities (DCV) in 24 men who were vibrating-tool operators and in 17 healthy adult men (control group). Of the 24 tool operators, 13 had a history of vibration-induced white finger [VWF(+) group] and 11 had no such history [VWF(−) group]. Two components of CVRR, i.e. C-CVRSA and C-CVMWSA, which have been considered to reflect parasympathetic and sympathetic activities, respectively, were also examined. Both the CVRR and the C-CVRSA in the VWF(+) group and the CVRR in the VWF(−) group were found to be significantly depressed as compared with the control values; moreover, a significant difference in the C-CVRSA was observed between the VWF(+) group and the VWF(−) group. The faster DCVs and the sensory median nerve conduction velocity were significantly slowed in the VWF (+) and VWF(−) groups. The C-CVMWSA was significantly correlated with most of the DCV parameters and with the median nerve conduction velocities in all 24 vibrating-tool operators. These data suggest that operation of vibrating tools, which involves exposure to combined stressors of local vibration, heavy work, climate, and noise, affects both the faster myelinated nerve-fiber activity and the parasympathetic activity; the sympathetic activity at rest in workers exposed to hand-arm vibration may be related to depression of peripheral nerve conduction.