Experimental Models for Drug Evaluation in Noise-Induced Hearing Loss and Age-Related Hearing Impairment

The contributions of noise and aging to hearing loss are distinct, yet interrelated. Noise-induced hearing loss (NIHL) is one of the leading – but preventable – causes of hearing loss worldwide. NIHL is usually characterized by an elevation in the hearing threshold, and the area of damage is most pronounced one-half octave above the frequency of noise exposure. A significant body of evidence suggests that NIHL damage results from noise-induced free radical production (Oishi and Schacht 2011). Age is an independent risk factor for acquired hearing loss, although its effects may be difficult to distinguish from those of noise exposure in the clinical setting. The mechanism underlying age-related hearing loss (presbycusis) is heavily influenced by an individual’s genetic susceptibility, and there is thus dramatic variation. Four-way cross animal models allow a longitudinal examination of these factors in relation to age and hearing loss.