Association between polymorphism of interleukin-6 in the region -174G/C and tinnitus in the elderly with a history of occupational noise exposure

Abstract

Tinnitus is a symptom usually related to cochlear change that may arise from noise exposure and induces expression of proinflammatory cytokines including interleukin-6 (IL6). This study aimed to evaluate the association between the polymorphism of the IL6 gene in the region 174G/C and tinnitus in elderly with history of occupational noise exposure.

Settings and design: This was a cross-sectional study with a sample of 179 independent elderly individuals aged >60 years. Information on exposure to occupational noise was obtained by interviews. Audiological evaluation was performed using pure tone audiometry and genotyped through polymerase chain reaction by restriction fragment length polymorphism (PCR-RFLP). Data were analyzed using the chi-square test and the odds ratio (OR), with the significance level set at 5%. Among the study subjects, 24.6% were homozygous for the G allele, 39.7% were homozygous for the C allele, and 35.8% were heterozygous for IL6 (P > 0.05). Of these, 33.5% reported noise exposure history, with 42.5% having tinnitus. We found significant association between the genotype and allele frequencies of the IL6 -174 gene (rs1800795) and tinnitus among the elderly with history of exposure to occupational noise (P = 0.03). The elderly with the C allele were less likely to have tinnitus associated with history of exposure to occupational noise [OR = 0.167, confidence interval (CI) 95% 0.167-0.749; P = 0.004] when compared to those carrying the G allele. This study suggests that there is an association between polymorphisms in the IL6 gene at region - 174G/C and susceptibility to tinnitus.