Incidence of hearing decline in the elderly

Pure-tone audiometry was done on 1475 persons on two occasions 6 years apart by the same audiologist in the same facility. The age of the subjects ranged from 58 to 88 years at the initial testing and 63 to 95 at the second. The average 6-year threshold change ranged from 1 to 8 dB at 250-6 kHz and 10-15 dB at 8 kHz. The differences in thresholds fell into two patterns, one for low frequencies (250-1 kHz) and the other for high frequencies (4-8 kHz). For the lows, thresholds worsened at an increasing rate with increasing age independent of the initial hearing level, and women's thresholds worsened more than men's. For the highs, the rate of threshold change decreased with age and with the initial threshold at rates that did not differ between genders. Using a change in PTA (0.5, 1, 2 kHz) of greater than 10 dB as a criterion, significant worsening occurred in the right ear in 8.5%, in the left ear in 13.5%, and in both ears of 4.1% of the subjects over the 6 year period. The rate of significant worsening increased with age. Although hearing loss increased with age, age alone accounted for less than 10% of the variance. Therefore, factors that co-vary with age may be responsible. The difference in phenomena between the low frequencies and the highs suggests that two different processes are occurring. Hair-cell degeneration is the most likely cause for the change in the high frequencies. Strial atrophy or other intracochlear processes may be the cause of the low frequency changes.