Hearing loss in the elderly and its compensation with hearing aids

Abstract

Hearing loss is common in the elderly, and the degree of loss tends to increase with increasing age. By 70 years of age, the majority of people have a hearing loss sufficient to cause communication problems in everyday life. The loss is typically greatest at high frequencies. The major cause of hearing loss in the elderly is loss of function of the hair cells within the cochlea. Reduced function of the outer hair cells (OHCs) results in loss of sensitivity (elevated absolute thresholds), reduced frequency selectivity, and loudness recruitment. Reduced function of the inner hair cells (IHCs) causes basilar-membrane (BM) vibrations to be transduced less efficiently and may lead to “noisy” transmission of information in the auditory nerve. In extreme cases, the IHCs may be completely non-functioning over a certain region of the BM, leading to a “dead region” in which there is no transduction. Current hearing aids can partially compensate for loss of sensitivity, by providing frequency-selective amplification, and for the effects of loudness recruitment by using compression amplification. This reduces the need to adjust the volume control to deal with different listening situations. The deleterious effects of reduced frequency selectivity on speech intelligibility in noise can be alleviated by various methods for improving the speech-to-noise ratio, although so far only directional microphones have given clear benefits. Hearing aids are usually of limited benefit for people with extensive dead regions, but for those with profound or total hearing loss cochlear implants may be of benefit. Improving the acoustics of meeting places and reducing background sounds in broadcasts could be of considerable benefit to all elderly people, regardless of whether or not they use hearing aids.