Association between vibration-induced white finger and hearing loss in forestry workers.

The present investigation was a case-referent study in which age and hours of vibrating tool operation were matched for the cases and referents in an effort to confirm the earlier reported difference in hearing loss between workers with vibration-induced white finger (VWF) and those without VWF. Thirty-seven pairs were formed from 51 men with VWF and 228 without it. The greatest hearing loss was at 4 kHz in both the case and reference groups, as is usually found in typical noise-induced hearing loss. The case group had a higher hearing threshold than the reference group at every frequency, and the difference was significant at 4 and 8 kHz and almost so at 2 kHz. As corroboration for this association, the subjects were divided into three groups by recovery rate of skin temperature 5 min after cold provocation at 10 degrees C for 10 min, a procedure which is one of the valid objective tests for VWF. The subjects with the most delayed recovery reached the highest age-corrected median hearing level at 4 kHz, and those with the promptest recovery marked the lowest. The cause of this increased damage of hearing in relation to VWF is not known. However, the association between VWF and hearing loss is interesting in view of the effects of vibration on parts of the body other than the hand and arm.