Demonstration of presbycusis across repeated measures in a nonhuman primate species.

The progress of age-related hearing loss in three 31-yr-old, two 24-yr-old, and two 9-yr-old rhesus monkeys (Macaca mulatta) was repeatedly examined over a period of 3 yr. Pure-tone audiograms for seven frequencies, .125, .500, 2.000, 4.000, 16.000, 22.667, and 32.000 kHz, were obtained through the use of the psychophysical tracking method. Analysis indicated the presence of presbycusis in the older animals. Animals demonstrating presbycusis showed a progressive decrement in the ability to detect higher frequencies and an overall hearing loss at all frequencies.