**7. References**


**Part 4** 

**Genetics**


**Part 4** 

208 Hearing Loss

Cova LJ, Márquez JJ, Tovar R. (2001). Interpretación Catastrófica de un Análisis de

Cox DR & Snell DJ. (1989). *Analysis of Binary Data*. Chapman & Hall, ISBN 9780412306204,

Ferrite S & Santana V. (2005). Joint Effects of Smoking, Noise Exposure and Age on Hearing

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Godderis L, Deschuyffeleer T, Roelandt H. (2008). Exposure to Metalworking Fluids and

Greenland S. (1994). Alternative Models for Ordinal Logistic Regression. *Statistics in Medicine*, Vol. 13, Nº16, (August 1994), pp. 1665-1677, ISSN 1097-0258 Gwin KK, Wallingford KM, Morata TC, Campen LE van, Dallaire J, Alvarez FJ. (2005).

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*Event Data*. Wiley, ISBN 0471154105, New York, EEUU

14, Nº 10, (October 1999), pp. 645-655, ISSN 1047-322X

de Estadística, Nº 27, ISBN 847133738X, Madrid, España

0161-813X

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Respiratory and Dermatological Complains in a Secondary Aluminium Plant. *International Archives of Occupational and Environmental Health*, Vol. 81, Nº 7, (July

Ototoxic Occupational Exposures for a Stock Car Racing Team: II. Chemical Surveys. Journal of Occupational and Environmental Hygiene, Vol. 2, Nº 8,

Classification of Pure Tone Screening Audiometry Results in Noise Exposed Groups. *Acta Oto-Laryngologica*, Vol. 75, Nº 2-6, (January 1973), pp. 339-340, ISSN 0001-6489 Martín Q y de Paz YR. *Aplicación de las Redes Neuronales Artificiales a la Regresión*. (2007). La Muralla, Col. Cuadernos de Estadística, Nº 35, ISBN 9788471337672, Madrid, España Mizoue T, Miyamoto T, Shimizu T. (2003). Combined Effect of Smoking an Occupational

Exposure to Noise on Hearing Loss in Steel Factory Workers. *Occupational and Environmental Medicine*, Vol. 60, Nº 1, (January 2003), pp. 56-59, ISSN 1097-9212 Morley JC, Seitz T, Tubbs R. (1999). Carbon Monoxide and Noise Exposure at a Monster

Truck and Motocross Show. *Applied Occupational and Environmental Hygiene*, Vol.

Occupational Noise Exposure on Hearing Loss: a Cross-Sectional Study. *BMC Public Health*, Vol. 7, Nº 3, Article Number 137, (July 2007), pp. 137, ISSN 1471-2458

after an Accident Exposure to Welding Fumes. *International Archives of Occupational and Environmental Health*, Vol. 80, Nº 7, (July 2007), pp. 635-641, ISSN 0340-0131 Silva LC y Barroso IM. (2004). *Regresión Logística*. La Muralla / Hespérides, Col. Cuadernos

(2008). Epidemiology of Noise-Induced Hearing Loss in New Zealand. *New Zealand* 

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Rothman KJ. (1986). *Modern Epidemiology*. Little-Brown, ISBN 9780316757768, Boston, EEUU Schaller KH, Csanady G, Filser J, Jüngert B, Drexler B. (2007). Elimination Kinetics of Metals

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Scuola Normale Superiore di Pisa, ISBN 9788876422928, Pisa, Italia

**Genetics**

**11** 

*1Japan 2Iran* 

**Genetics of Hearing Loss** 

Nejat Mahdieh1,2, Bahareh Rabbani1 and Ituro Inoue1

*1Division of Human Genetics, National Institute of Genetics, Mishima, Shizuoka,* 

*2Medical Genetic Group, Faculty of Medicine, Ilam University of Medical Sciences, Ilam,* 

Hearing loss (HL) is the most common sensory defect in human beings, affecting 1.86 in 1000 newborns around the *world* which half of it is due to genetic causes (Morton & Nance, 2006). HL can be syndromic or nonsyndromic. Individuals affected with syndromic form have additional clinical signs whereas nonsyndromic HL is not associated with other clinical signs and symptoms. All Mendelian pattern of inheritance have been observed in nonsyndromic HL (NSHL) including autosomal dominant (AD), autosomal recessive (AR), X-linked inheritance (XL) and mitochondrial inheritance (MT); autosomal recessive is the main form of NSHL, i.e. 75-85 % of NSHL show AR pattern in

As known, ear is the organ of hearing and balance. Hearing is dependent on a series of complex events. The ear has three anatomical parts including outer, middle and inner ear. The external ear which is composed of the auricle, ear canal and eardrum membrane collects sound waves and transmits them to the eardrum. Three tiny bones of middle ear (the ossicles) act as levers and conduct the sounds to the oval window, and finally through the cochlea (a snail-shaped organ) which has the auditory receptors (the organ of Corti) in the inner ear [Raphael & Altschuler 2003]. A collagen-based extracellular matrix, called tectorial membrane on top of the hair cells is vibrated by sound waves [Richardson et al., 2008]. Within the organ of Corti, physical vibrations produce a mechanoelectrical transduction which is detected by hair cells and these cells respond by producing electrical impulses. Nerves transmit these impulses to the brain where they are interpreted. Different sound frequencies stimulate the hair cells in different parts of the organ of Corti and lead to perception of different sound frequencies. Sounds are processed in both sides of the brain but the interpretation of the sounds takes place at the left side of brain. Sounds are heard at normal hearing thresholds between 0-20 dB across the 125-8000 Hz range while loss of more than 20 dB, is said to have hearing loss which is confirmed by measuring pure tone average (PTA) (average hearing sensitivity at 500, 1000

Nearly one hundred and twenty million people suffer from hearing impairment around the world. History of some important events about human hereditary HL is shown in table 1 [Nance & Sweeney, 1975; Wallis et al., 1988; Kimberling et al., 1990; Leon et al., 1992;

**1. Introduction** 

affected pedigrees.

and 2000 Hz).
