Vibration perception thresholds in workers exposed to vibration.

The vibration perception thresholds (VPT) at six frequencies from 16 to 500 Hz were examined in 77 workers exposed to hand-arm vibration and in 77 controls using a limits procedure. A dose-response relationship between VPTs and exposure to vibration was found, and the age-adjusted VPTs at each frequency were higher in workers exposed to vibration than in controls. Carpal tunnel syndrome (at 250 Hz) and consumption of alcohol (at 125 Hz) significantly increased the VPT, but vibration-induced white finger was not correlated with VPT. Indices for low (16 and 32 Hz) and high (63-500 Hz) VPT frequencies were calculated to evaluate the entire vibrogram, which consisted of several frequencies with two numbers. The results showed that hand-arm vibration disturbs first the high frequencies, and that the disturbance spreads thereafter to the low frequencies. The characteristics of the VPT test regarding vibration exposure and the association between VPT and nerve symptoms in the hand support the view that VPT is a useful measure for vibration-induced sensory nerve damage.