Evaluation of individual susceptibility to noise-induced hearing loss in textile workers in China

The authors applied noise exposure and audiometry information collected on 156 Chinese textile workers to develop a method of identifying individuals susceptible to noise-induced hearing loss. They estimated noise-induced hearing threshold shift (NIHTS) by averaging the adjusted hearing thresholds at 3, 4, and 6 kHz of both ears, and they fitted a quadratic model to describe the dose-response relationship between cumulative noise exposure and NIHTS. The residual between the actual NIHTS and the model-predicted NIHTS indicated susceptibility. A comparison of the 20% of the subjects with the greatest residuals (those who were susceptible to hearing loss) with the 20% of the subjects with the smallest residuals (those who were resistant to hearing loss) revealed that the former had poorer hearing, although the noise exposures were similar. The identified susceptible individuals also had the poorest hearing thresholds within each subgroup of homogenous noise exposures. With their model-based procedure, the authors were able to identify individuals susceptible to noise-induced hearing loss from subjects with heterogeneous noise exposures.