Relationship between individual susceptibility to noise-induced hearing loss and vibration-induced white finger and neurological disorders

Carnicelli, Maristela Vendramel Ferreira (1992) Relationship between individual susceptibility to noise-induced hearing loss and vibration-induced white finger and neurological disorders. University of Southampton, Doctoral Thesis.

Abstract

The objective of this study was to investigate the relationship between individual susceptibility to noise-induced hearing loss (NIHL) and vibration-induced white finger (VWF) and neurological disorders. The main hypothesis was that there is not a common individual susceptibility to noise and hand-transmitted vibration. In order to achieve this objective a model of differential damage susceptibiity was adopted. This model has been suggested and applied in previous studies of individual susceptibility to noise. However, it was not known if it could be applied to hand-transmitted vibration. A subsidiary issue was to determine which battery of tests would be suitable to assess and/or convey information on individual susceptibility to vibration-induced white finger and neurological disorders. As there is no specific test or battery of tests available to investigate susceptibility to vibration-induced white finger and neurological disorders, some procedures commonly used in the diagnosis of these diseases were selected based on theoretical inferences that could convey relevant information on susceptibility. The repeatability of these vascular (finger systolic blood pressure and finger rewarming measurements) and neurological (aesthesiometry and vibrotactile thresholds) tests was investigated in two different experiments. Finger systolic blood pressure (FSBP% ₁₅) and vibrotactile thresholds were the procedures which showed less variability of results when applied in different occasions. The hearing and vascular and neurological functions of 61 young healthy subjects were analyzed and no correlations found between test results. This suggests that NIHL and VWF and vibration-induced neurological disorders are independent and a common susceptibility to damage seems to be very unlikely. The hearing threshold levels of VWF and neurological survivors subjects were also investigated. It was found that subjects showed a spread of hearing threshold levels, some subjects presenting normal threshold levels and others with thresholds indicative of noise-induced hearing loss. Therefore, the hand-transmitted vibration survivors were not noise survivors. These findings support the hypothesis that a common individual susceptibility to noise-induced hearing loss and vibration-induced white finger and neurological disorders is unlikely to exist.

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