The authors define the term presbycusis and discuss the prevalence of hearing loss in elderly people, its etiology, and methods of diagnostics (anamnesis, evaluation of the peripheral and central parts of the hearing system). The authors emphasize that central auditory processing disorder (CAPD) significantly impairs speech perception in elderly people and makes difficult the rehabilitation of patients with presbycusis. The possibility of improving speech intelligibility by using auditory

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... ng is considered. Improved functioning of the central auditory pathways in hearing aid (HA) users with moderate to moderately severe chronic sensorineural hearing loss (SNHL) and symptoms of CAPD was shown after the auditory training with the use of two approaches ("bottom-up" and "top-down"). The algorithm of the auditory training was designed based on distinction between nonverbal and verbal stimuli of varying complexity, as well as tasks to improve memory (e.g., memorizing poetry). The benefits of the auditory training in the rehabilitation of HA users with low speech intelligibility were demonstrated. Improvement of speech intelligibility in elderly patients with SNHL proves that plasticity of the auditory regions of the brain remains possible throughout the life. Options of the presbycusis prophylaxis are summarized. Different authors sometimes interpret this term differently. Some researchers meant (imply under this term) age-related hearing disorders caused by involutional changes only in the cochlea, and others meant that changes involve all parts of the auditory system [1, 2] . Presbycusis is considered to be one of the forms of progressive SNHL, which is associated with age-related involutional changes of different parts of the hearing system and is presented by symmetric pure tone audiogram with flat loss toward high-frequency range (less steep than 20 dB/oct) [3] . Numerous studies are dedicated to anatomical and functional risk factors of the presbycusis [4] [5] [6] [7] [8] [9] . The significance of the presbycusis problem is determined by its social importance, lack of data about its etiology, and need for clinical practice to accurately determine an impaired area of auditory system and to identify the presbycusis genesis. Prevalence Presbycusis is a rather common disorder. According to the World Health Organization (WHO), more than 5% of global population (about 328 millions of adults) suffers from any degree of hearing loss, while among people older than 65 years of age, the prevalence of hearing loss exceeds 30% [10]. Its prevalence increases every year that may be due to the general trend of increased life duration-much more adults reach aged (from 60 to 74 years old according to the WHO classification) and senile (75 years old and more) periods. The world population is rapidly aging. At the period between 2000 and 2050, the proportion of the world's population over 60 years will double from about 11 to 22%. The absolute number of people aged 60 years and over is expected to increase from 605 million to 2 billion over the same period. The number of people aged 80 years or older will have almost quadrupled between 2000 and 2050 to 395 million [11] . Approximately one in three people in the United States between the age of 65 and 74 has hearing loss, and nearly half of those older than 75 have difficulties in hearing. Having trouble hearing can make it hard to understand and follow a doctor's advice, respond to warnings, and hear phones, doorbells, and smoke alarms. Hearing loss can also make it hard to enjoy talking with family and friends, leading to feelings of isolation. Etiology There are many causes of age-related hearing loss. Most commonly, it not only arises from changes in the inner ear as we age but can also result from changes in the middle ear, or from multiple changes that occur along the nerve pathways directed toward the brain from the inner ear. Associated medical conditions and some medications may also exert an influence. Many factors can contribute to hearing loss as you get older. It can be difficult to distinguish age-related hearing loss and hearing impairment caused by other reasons, for example, noiseinduced hearing loss. Noise-induced hearing loss is caused by long-term exposure to sounds that are either too loud or last too long. This kind of noise exposure can damage the sensory hair cells of the inner ear and is responsible for hearing loss. Once these hair cells are damaged, they do not grow back, and the ability to hear is diminished. Gerontology 64 Gerontology 66 Characteristics of Hearing in Elderly People http://dx.doi.org/10.5772/intechopen.75435 77 Gerontology 80