The main findings of our study were that the risk of developing hearing impairment in middle-aged and elderly subjects is influenced by an interaction between the MTR A2756G and MTHFR C677T gene polymorphisms and that the MTHFR 677T allele is associated with a reduced risk of hearing impairment, but only when the MTR A2756G genotype is a wild-type homozygote (AA). The gene discussed is MTHFR; the disease is hearing loss disorder.