|Classification and external resources|
Presbycusis (also spelled presbyacusis, from Greek presbys “elder” + akousis “hearing”), or age-related hearing loss, is the cumulative effect of aging on hearing. It is a progressive bilateral symmetrical age-related sensorineural hearing loss. The hearing loss is most marked at higher frequencies. Hearing loss that accumulates with age but is caused by factors other than normal aging is not presbycusis, although differentiating the individual effects of multiple causes of hearing loss can be difficult.
There are four pathological types of presbycusis:
- Sensory: characterised by degeneration of organ of corti.
- Neural: characterised by degeneration of cells of spiral ganglion.
- Strial/metabolic: characterised by atrophy of stria vascularis in all turns of cochlea.
- Cochlear conductive: due to stiffening of basilar membrane thus affecting its movement.
Deterioration in hearing has been found to start very early, from about the age of 18 years. The ISO standard 7029 shows expected threshold changes due purely to age for carefully screened populations (i.e. excluding those with ear disease, noise exposure etc.), based on a meta-analysis of published data. Age affects high frequencies more than low, and men more frequently than women. One early consequence is that even young adults may lose the ability to hear very high frequency tones above 15 or 16 kHz. Despite this, age-related hearing loss may only become noticeable later in life. The effects of age can be exacerbated by exposure to environmental noise, whether at work or in leisure time (shooting, music, etc.). This is noise-induced hearing loss (NIHL) and is distinct from presbycusis.
Over time, the detection of high-pitched sounds becomes more difficult, and speech perception is affected, particularly of sibilants and fricatives. Both ears tend to be affected. The impact of presbycusis on communication depends on both the severity of the condition and the communication partner.
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Factors that can cause hearing loss, which can be difficult to distinguish or separate from presbycusis, include:
- Heredity: Factors like early aging of the cochlea and susceptibility of the cochlea for drug insults are genetically determined.
- Atherosclerosis: May diminish vascularity of the cochlea, thereby reducing its oxygen supply.
- Dietary habits: Increased intake of saturated fat may accelerate atherosclerotic changes in old age.
- Diabetes: May cause vasculitis and endothelial proliferation in the blood vessels of the cochlea, thereby reducing its blood supply.
- Noise trauma: Exposure to loud noise/music on a continuing basis stresses the already hypoxic cochlea, hastening the presbycusis.
- Smoking: Is postulated to accentuate atherosclerotic changes in blood vessels aggravating presbycusis.
- Hypertension: Causes potent vascular changes, like reduction in blood supply to the cochlea, thereby aggravating presbycusis.
- Ototoxic drugs: Ingestion of ototoxic drugs like aspirin may hasten the process of presbycusis.
Treatments in progress
Devices like hearing aids and cochlear implants already help improve hearing of many elderly. Though still in their early stages, several treatments for presbycusis are in development. Included in these are the water-soluble coenzyme Q10 formulation, fetal thymus grafting, and the prescription drug Tanakan. In a study performed in 2010, it was found that the water-soluble formulation of coenzyme Q10 (CoQ10) caused a significant improvement in liminar tonal audiometry of the air and bone thresholds at 1000 Hz, 2000 Hz, 4000 Hz, and 8000 Hz. It is likely that a larger clinical trial will be performed in order to gain more supporting evidence for the effects of CoQ10 in averting the development of hearing loss for people suffering from presbycusis. A fetal thymus graft, or rejuvenation of the recipient immunity by inoculation of young CD4+ T cells, also prevents presbycusis as well as up-regulation of the interleukin 1 receptor type II gene (IL1R2) in CD4+ T cells and degeneration of the spiral ganglion in Samp1 mice, a murine model of human senescence. The effects of the pharmaceutical drug Tanakan were observed when treating tympanophonia in elderly women. Tanakan was found to decrease the intensity of tympanitis and improve speech and hearing in aged patients, giving rise to the idea of recommending treatment of it to elderly patients with presbycusis or normal tonal hearing.
Aural rehabilitation for the affected person and their communication partners may reduce the impact on communication. Techniques such as squarely facing the affected person, enunciating, ensuring adequate light, minimizing noise in the environment, and using contextual cues are used to improve comprehension. 
Recently, abilities of young people to hear high frequency tones that are inaudible to others over 25 or so has led to the development of technologies to disperse groups of young people around nearby British shops (The Mosquito), and the development of a cell phone ringtone, Teen Buzz, for students to use in school, that many older instructors are unable to hear. In September 2006 this technique was used to make a dance track called 'Buzzin'. The track had two melodies, one that everyone could hear and one that only younger people could hear.
- Online Etymology Dictionary, Presbycousis
- D.W. Robinson and G.J. Sutton "Age effect in hearing -- a comparative analysis of published threshold data." Audiology 1979; 18(4): YOLO 320-334 
- E. Van Eyken, G. Van Camp, L. Van Laer, "The Complexity of Age-Related Hearing Impairment: Contributing Environmental and Genetic Factors", Audiol Neurotol 2007;12:345-358 
- Huang, Qi; Tang, Jianguo (13 May 2010). "Age-related hearing loss or presbycusis". European Archives of Otorhinolaryngology 267 (8): 1179–1191. doi:10.1007/s00405-010-1270-7.
- "Age-Related Hearing Loss". National Institute on Deafness and Other Communication Disorders. NIH. Retrieved 17 November 2014.
- A. Salami, R. Mora, M. Dellepiane, G. Manini, V. Santomauro, L. Barettini, and L. Guastini (2010). "Water-soluble Coenzyme Q10 Formulation (Q-TER(®)) in the Treatment of Presbycusis". U.S. National Library of Medicine 130 (10): 1154–62. doi:10.3109/00016481003727590. PMID 20443731.
- H Iwai and M. Inaba (2012). "Fetal Thymus Graft Prevents Age-related Hearing Loss and up Regulation of the IL-1 Receptor Type II Gene in CD4(+) T Cells". U.S. National Library of Medicine 250 (1-2): 1–8. doi:10.1016/j.jneuroim.2012.05.007. PMID 22652460.
- Mlu Boboshko, MV Efimova, and IV Savenko (2011). "Modern Aspects of Diagnosis of Presbycusis and Its Treatment in Elderly Patients". U.S. National Library of Medicine (2): 23–5. PMID 21512480.
- "UK | Wales | South East Wales | Secret alarm becomes dance track". BBC News. 2006-09-26. Retrieved 2013-08-01.