Vibration-induced white finger as a risk factor for hearing loss and postural instability

Effect of vibration-induced white finger (VWF) on the hearing was examined in 289 Japanese forest workers. From 51 subjects suffering from VWF and 228 with no history of VWF, 37 pairs were formed, matched for age and hours of noise exposure. The cases with VWF had a significantly higher hearing threshold at 4 and 8 kHz than their matched controls. This result was corroborated by the follow-up study which showed significant deterioration of hearing at 2 and 4 kHz only in subjects with VWF during five-year follow-up period. The possible effects of VWF on the postural stability were investigated in 71 Finnish forest workers. Postural stability was evaluated by an average velocity of the body-sway (ASV) measured with a force platform technique. Neither age nor exposure duration to chain saw noise and vibration correlated with ASV. A significant positive correlation was found between ASV and hearing level at 4 kHz after allowing for the effects of the exposure. Multiple regression analysis of ASV on age, exposure hours, hearing level at 4 kHz and prevalence of VWF showed that the hearing level and VWF had significant and almost significant effects on ASV, respectively. Thus, the workers suffering from VWF developed greater hearing loss and the hearing loss correlated with ASV. VWF explained some variance of ASV in the regression analysis. VWF seemed to play some role in hearing deterioration and possibly in genesis of balance disorder.