Objectives: Noise-induced hearing loss (NIHL) is a complex disease resulting from the interaction between external and intrinsic/genetic factors. Based on mice studies, one of the most interesting candidate gene for NIHL susceptibility is CDH23-encoding cadherin 23, a component of the stereocilia tip links. The aim of this study was to analyze selected CDH23 single nucleotide polymorphisms (SNPs) and to evaluate their interaction with environmental and individual factors in respect to susceptibility for NIHL in humans.
Methods: A study group consisted of 314 worst-hearing and 313 best-hearing subjects exposed to occupational noise, selected out of 3,860 workers database. Five SNPs in CDH23 were genotyped using real-time PCR. Subsequently, the main effect of genotype and its interaction with selected environmental and individual factors were evaluated.
Results: The significant results within the main effect of genotype were obtained for the SNP rs3752752, localized in exon 21. The effect was observed in particular in the subgroup of young subjects and in those exposed to impulse noise; CC genotype was more frequent among susceptible subjects, whereas genotype CT appeared more often among resistant to noise subjects. The effect of this polymorphism was not modified by none of environmental/individual factors except for blood pressure; however, the latter one should be further investigated. Smoking was shown as an independent factor determining NIHL development.
Conclusion: The results of this study confirm that CDH23 genetic variant may modify the susceptibility to NIHL development in humans, as it was earlier proven in mice. Because the differences between the 2 study groups were not necessarily related to susceptibility to noise but they also were prone to age-related cochlear changes, these results should be interpreted with caution until replication in another population.