Vibration Syndrome in the Etiology of Occupational Hearing Loss

Abstract

The connection of noise-induced permanent threshold shift (NIPTS) and the vasospastic component of vibration syndrome was studied. The purpose of the longitudinal study was to detect whether vibration-induced circulatory disturbances (VWF) in the fingers are generalized and whether VWF indicates increased hearing loss in lumberjacks. The lumberjacks studied (N = 72 in 1972; 203 in 1978) were classified according to history of VWF, exposure time, age and the use of ear protectors. The hearing level at 4,000 Hz was used to indicate NIPTS. The personal exposure to noise was L_eq 96–103 dB (A). A statistically significant hearing difference was found between lumberjacks with and those without VWF. The findings indicate that circulatory disturbances in the fingers are connected to occupational hearing loss; thus, the harmful effects of local vibration are not restricted to the hand-arm system. The proposed etiological mechanism for NIPTS may be similar to the one proposed for VWF: chronic overexcitation of the sympathetic nervous system.