Interleukin-1 Alpha Gene Polymorphism (IL-1α) and Susceptibility to Tinnitus in the Elderly

CONTEXT: To investigate the association between the single nucleotide polymorphism in the position-889 (C/T) of the promoter region of the IL-1α gene and the susceptibility to tinnitus. METHOD: This was a case-control study with a sample of 108 independent elderly people over 60 years of age. Information on exposure to occupational noise and tinnitus was obtained by interviews. The genetic polymorphism was analyzed by polymerase chain reaction followed by cleavage with restriction enzyme NcoI. Data were analyzed using the Chi-square test, with the significance level set at 5%. For the statistical analysis all individuals with tinnitus on the right ear were eligible. RESULTS: Among elderly with tinnitus, 42.9% had a history of exposure to occupational noise. There was statistically significant association between IL-1α gene polymorphism and tinnitus in subjects without a history of exposure to occupational noise (P = 0.006 and χ(2) = 10.39). The elderly with the T allele were less likely to have tinnitus due to occupational noise exposure when compared to those carrying the C allele. CONCLUSION: This study suggests an association between the IL-1α gene polymorphism with susceptibility to tinnitus in individuals without a history of exposure to occupational noise. The present study demonstrated that allele T of IL-1α is a protective factor for presence and severity of tinnitus in the elderly and allele C contributes to the pathogenesis of the inflammatory response. The present observation implied the signaling IL-1α is involved in ear aging.