Effects of Aging on Brainstem Responses to Toneburst Auditory Stimuli: A Cross-Sectional and Longitudinal Study in Dogs

Background: It is assumed that the hearing of dogs becomes impaired with advancing age, but little is known about the prevalence and electrophysiologic characteristics of presbycusis in this species. Hypothesis: As in humans, hearing in dogs becomes impaired with aging across the entire frequency range, but primarily in the high‐frequency area. This change can be assessed quantitatively by brainstem‐evoked response audiometry (BERA). Animals: Three groups of 10 mixed‐breed dogs with similar body weights but different mean ages were used. At the start of the study, the mean age was 1.9 years (range, 0.9–3.4) in group I, 5.7 years (3.5–7) in group II, and 12.7 years (11–14) in group III. Methods: In a cross‐sectional study, the BERA audiograms obtained with toneburst stimuli were compared among the 3 groups. In a longitudinal study, changes in auditory thresholds of group II dogs were followed for 7 years. Results: Thresholds were significantly higher in group III than in groups I and II at all frequencies tested, and higher in group II than in group I at 4 kHz. The audiograms in group II indicated a progressive increase in thresholds associated with aging starting around 8–10 years of age and most pronounced in the middle‐ to high‐frequency region (8–32 kHz). Conclusions and Clinical Importance: Age‐related hearing loss in these dogs started around 8–10 years of age and encompassed the entire frequency range, but started and progressed most rapidly in the middle‐ to high‐frequency area. Its progression can be followed by BERA with frequency‐specific stimulation.