The statistical analysis was performed using the statistical package SPSS 17.0 (SPSS Inc., Chicago, IL, USA). To test theassociation between genotype frequency and hearing loss related to a history of occupational noise exposure, the chis quare test was performed. The Hardy---Weinberg equi-librium was tested in each group using the chi-square test.The odds ratio (OR) with a confidence interval of 95% (95%CI) was calculated. The significance level was set at 5%.