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 Table of Contents  
ORIGINAL ARTICLE
Year : 2014  |  Volume : 3  |  Issue : 4  |  Page : 191-194

Hearing loss prevalence and risk factors among Iranian deaf children: The first report from Iran


1 New Hearing Technologies Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran
2 Chemical Injuries Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran
3 Behavioral Sciences Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran

Date of Web Publication14-Nov-2014

Correspondence Address:
Mohammad Ajalloueyan
New Hearing Technologies Research Center, Baqiyatallah University of Medical Sciences, Mollasadra St, Vanak Sq, Tehran
Iran
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2249-4847.144748

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  Abstract 

Background: There are many regional variations in the rate and predisposing factors of hearing loss and these could vary over time. The aim of this study was to describe the characteristics and possible etiology of severe to profound bilateral sensorineural hearing loss (SNHL) among Iranian children who were a candidate for cochlear implantation. Materials and Methods: We designed a cross-sectional study to evaluate children with profound SNHL referred to Baqiyatallah Cochlear Implantation Center from all over the country of Iran. Among 471 referred children, 310 cases with diagnosis of bilateral profound SNHL ranging in age from 6 months to 4 years between 2005 and 2011 were enrolled.
Results: The mean (±standard deviation) age of individuals and the mean age of diagnosis was 3.50 ± 1.23 and 164 (53%) were male. Considerable risk factors for SNHL in 218 patients (70.3%) were obvious. A total of 103 (33%) children had one or more close relatives with deafness in their family, so they were considered to be hereditary deafness cases, followed by prematurity 32 (10.3%), syndromic etiology 25 (8%), maternal toxoplasmosis, rubella, cytomegalovirus, herpes infection 12 (3.9%), severe hyperbilirubinemia 9 (3%), eruptive infections 9 (3%), meningitis 8 (2.6%), asphyxia 6 (2%), and oto-toxic drug 6 (2%). Our data showed the prevalence of 65% consanguineous marriage among parents of deaf children. Conclusion: This is the first attempt to describe the risk factor of SNHL in Iran. Among the identifiable causes of severe to profound SNHL in Iranian population, the consanguineous marriage was the most common risk factor. Further analytical studies focusing on the relation between etiology and demographic factors were recommended.

Keywords: Children, cochlear implant, consanguineous marriage, risk factors, sensory neural hearing loss


How to cite this article:
Amirsalari S, Saburi A, Radfar S, Yousefi J, Nouhi S, Hassanalifard M, Hosseini MJ, Ajalloueyan M. Hearing loss prevalence and risk factors among Iranian deaf children: The first report from Iran. J Clin Neonatol 2014;3:191-4

How to cite this URL:
Amirsalari S, Saburi A, Radfar S, Yousefi J, Nouhi S, Hassanalifard M, Hosseini MJ, Ajalloueyan M. Hearing loss prevalence and risk factors among Iranian deaf children: The first report from Iran. J Clin Neonatol [serial online] 2014 [cited 2021 Sep 21];3:191-4. Available from: https://www.jcnonweb.com/text.asp?2014/3/4/191/144748


  Introduction Top


Sensorineural hearing loss (SNHL) due to hereditary and environmental causes affects 1-3 of every 1000 children born in the developed countries [1],[2] and the rate is probably higher in the developing world. [3] In most of the cases, the HL is nonsyndromic, and the child is otherwise healthy. In fact, deafness disturbs appropriate communication and learning, necessary for the normal development and maturation of a child. The deaf child receives little or no access to environmental sounds; this lack of access arrests or disrupts normal auditory development. [4],[5],[6]

Epidemiologic surveys of HL in various parts of the world and among different ethnic groups with widely varying marital habits, socioeconomic status and environment not only help in understanding the frequency of the HL in specific areas, but also contribute to the general knowledge about the predisposing factors of the deafness. [5],[6],[7]

Some previous study estimated that about half of deaf individuals affected as infants or children have hereditary deafness. [7],[8] Moreover, one-third to one-half of cases detected in infancy have an environmental cause that in various countries, the cause of HL have been reported differently, with the most common cause being congenital cytomegalovirus infection. Congenital rubella syndrome, pharmacologic ototoxicity, neonatal asphyxia, and prematurity are other common causes. [1],[6],[7],[8],[9]

There may be regional variations in the rate and predisposing factors of HL and these could vary over time. [7],[8] Furthermore, there are many identified or unidentified risk factor in Iranian population for congenital or noncongenital deafness such as the higher rate of consanguineous marriage. The rate of consanguineous marriage in Iran was reported as 38.6%, which is more than many other countries. [10],[11] In order to determine the etiology and rate of deafness, studies on the prevalence and causes of deafness have to be done over several time periods in the different geographical area. [1] The main aim of this study was to demonstrate the causes of profound bilateral severe SNHL among Iranian children who were a candidate for cochlear implantation.


  Materials and methods Top


Our cross-sectional study was designed to collect information about profound hearing impaired cases referred from all over the country through the ear, nose, and throat (ENT) services to Baqiyatallah Cochlear Implantation Center. Among 471 children ranging in age from 6 months to 4 years with diagnosis bilateral profound hearing impairments that were referred to Baqiyatallah Cochlear Implantation Center, 310 cases were finally admitted to this study. The SNHL in all cases was confirmed by using auditory brain response and otoacoustic emission assessment test. The degree of profound HL should be defined in terms of dB. A uniform questionnaire was used for all the hearing impaired cases. All the details were filled up by the ENT surgeon himself and could be considered reliable from the otolaryngological examination point of view. The study included the cases collected between January 2005 and April 2011. The form included the demographic details and the other details relevant to the problem of hearing impairment; information about them was obtained from the parents, instructors and individual records. Data including a complete medical and family history as well as prenatal, natal, and postnatal risk factors were collected. Nongenetic environmental factors such as congenital rubella (prenatal), prematurity, birth asphyxia, kernicterus (perinatal), meningitis, head injury, consumption of ototoxic drugs and other infectious conditions (postnatal) causing hearing impairment were taken note of. A complete clinical examination was performed including general and systemic examination to rule out any congenital abnormality.

A careful physical examination involving systemic, otologic, and neuropsychiatric evaluation was carried out. Audiological investigations were conducted to evaluate and document the degree and type of HL; children needed brainstem evoked response audiometry, auditory brainstem response for confirmation of hearing impairment. If there were no risk factors and the child had deaf close relatives, the cause of deafness was decided as hereditary. This study was approved by Ethic Committee of Baqiyatallah University of Medical Sciences.

Using SPSS version 16 and frequency, percentage to analysis the data and Chi-square test was used to show whether there was any statistical difference between the incidence of marital consanguinity of parents in deaf patients and that rate in the normal population.


  Results Top


From 310 patients, 164 (53%) were male, and 146 (47%) were female. The mean (±standard deviation) age of individuals and the mean age of diagnosis of SNHL were 36.25 ± 21.53 and 17.65 ± 5.11 months. In 203 (65%) patients, parents had consanguineous marriages and 107 (35%) of parents marriages were not consanguineous.

A total of 103 (33%) out of 310 children had one or more close deaf relatives in their family, so they were considered to be hereditary deafness. A total of 203 (65%) of those 310 children had parents married with their relatives, whereas a marital consanguinity was noted among the parents. From the 203 (65%) patients parents that had consanguineous marriages 132 parents were first cousins that includes the children of two brothers (patrilateral parallel cousins) 37 (11.8%), the children of two sisters (multilateral parallel cousins) 38 (12.2%), or children of a brother and a sister (cross-cousins) 57 (18.3%), 54 (17.4%) of parents were second-cousins and the remains 17 (5.2%) parents were beyond second-cousins. The mean proportion of consanguineous marriages in Iran was 38.6%, ranging from 15.9% in the Northern Provinces to 47.0% in the Eastern Provinces. [10],[11] That was statistically different with our patients family (P = 0.01).

As it has shown in [Table 1], risk factors were shown in 218 (70.3%) of all patients with profound HL, but it was unknown in 92 (29.7%) patients [Table 1].{Table 1}

As it has shown in [Table 1], 103 (33%) children had one or more close deaf relatives in their family, so they were considered as hereditary deaf patients, followed by prematurity 32 (10.3%), syndromic cases 25 (8%), maternal toxoplasmosis, rubella, cytomegalovirus, herpes (TORCH) infection 12 (3.9%), hyperbilirubinemia 9 (3%), eruptive infections 9 (2.9%), meningitis 8 (2.6%), asphyxia 6 (2%), and ototoxic drug consumption 6 (2%). A total of 84 (32%) children were noticed by their families and seen by the doctors before the age of 1-year. Between the age of 12 and 30 months, 105 (40%) children were diagnosed, while 73 (28%) of all cases could not be identified by the age of 30 months.


  Discussion Top


This study is the first attempt of this kind in our country. As it shown in our result risk factors were obvious in 218 (70.3%) of all patients with profound HL, but it was unknown in 92 (29.7%) patients. Hereditary cause was identified as the most common cause that followed by prematurity, syndromic causes, maternal TORCH infections, severe hyperbilirubinemia, and eruptive infectious, meningitis, asphyxia, and ototoxic drugs.

Our data showed the prevalence of 65% consanguineous marriage among parents of deaf children. The overall rate of consanguineous marriages in our patients is much higher than the rate in the normal population. These findings showed the importance of consanguinity as a predisposing factor for the child's deafness. The mean proportion of consanguineous marriages in Iran was 38.6%. [10],[11]

Hereditary causes have been reported with various rates ranging from 10.2% in Olusanya and Newton study [12] to 66.1% in the study from Middle East in Saudi Arabia reported by Zakzouk et al. [13],[14] This relatively high-incidence of hereditary deafness may be explained by an increase of hereditary deafness cases due to consanguinity or of the improvement of detecting genetic deafness. [14]

Another study in our area was the study by Bener et al. from Qatar that in this study Parental consanguinity was more common among HL cases compared with nonHL (60.5% vs. 25.3%).

The effect of consanguinity on the genetic origin of deafness has been demonstrated in other parts of the world. [15]

32 (10.3%) of cases had prematurity, severe hyperbilirubinemia in 9 (3%) of cases and Asphyxia in 6 (2%) of cases that contains 15.3% of cases in our study. In a study conducted in schools for deaf in Elango et al., perinatal causes were identified in 19%. [16] In Dereköy study, identified perinatal causes in 12% of his cases. [17]

The syndromic HL was demonstrated in 25 (8%) of our cases. In other studies, the syndromic HL was identified in 1.3% [16] in Elango study in Malaysia, 3.8% in Dias and Andrea study, [18] and 30% in Reardon study [19] ototoxicity related hearing impairment is seen in 2% of our patients. It contributes to a significant degree in some other developing world. [16],[17],[20],[21]

That seems there are ways to prevent part of the environmental and hereditary deafness in a population by the prevention of specific diseases and by genetic counseling, but the problem of differentiating the prenatal from the perinatal causes remains a challenge. The higher is the age at diagnosis the more are chances of a case falling into the group of undiagnosed cases and in spite of the comprehensive evaluation, the search for etiology remains inconclusive in 30-40% of the cases. [6]

In our study, the search for etiology remains inconclusive in 92 (29.7%) patients. This finding is in line with different study in this matter the Derekoy's Study in Turkey reported that the cause of deafness was unknown in 33% of the children. [16] This rate of unknown causes was similar to that of Das [27] of 34%, and more than the 20% observed by Parving, [22] 21% observed by  Egeli et al., [23] and 22% observed by Vartiainen et al. [24] in moderate to severe deaf children. In fact, the group ''unknown'' is the challenge for most of the investigators. There is a constant effort to reduce the size of this group. However, it still forms a large portion in most of the studies. Several authors assume that the majority of the unknown group represents autosomal recessive HL, others are believe that silent infections like cytomegalovirus are to be blamed for a significant part of this group. [1],[6],[16]

In our study, history of maternal TORCH infection was obtained in 3.9% of cases. However, it is hard to know whether the infection is congenital or acquired in a deaf child.

On the other hand, the diagnosis of congenital TORCH syndrome is often difficult and made on history and clinical findings. Martin [25] described rubella as being the most common identifiable cause of congenital SNHL in children. Janzen and Schaefer [26] determined 33 maternal rubella cases (19%), as Das [27] in his study, found congenital rubella infection in 18 children (5.3%) and reported that the number of congenital rubella cases continued to decrease. We had no any maternal rubella case as a deafness cause.

In this study, the incidence of meningitis and eruptive Infections such as measles was found to be 2.6% and 2.9% of our cases, meningitis and measles are the other important diseases which cause hearing impairment. The studies from Turkey showed a rate from 4.8% to 23.4%. In a study conducted in Malaysia by Elango et al., [16] have reported that 20 children (12.1%) had meningitis, as 5.3% was found by Gray in Madras. [21] In another study, Holborow et al. [26] reported that an incidence of 18% was noted following meningitis and 19% following measles.

In our study, deafness in 8 (2.6%) cases was attributed to eruptive infections. This rate was 6% in the study from Turkey. Minja [20] in his study found that the cause was meningitis in 23.9% while measles in 4.1% in Tanzania. In Robarts School for the deaf, the incidence was 8% for meningitis and 2% for measles. [18]


  Conclusion Top


Hereditary factor was the major causes of deafness in this study. The high-incidence of the consanguineous marriage among the parents of deaf children showed a genetic origin. Decreasing the prevalence rate of consanguineous marriage will be helpful to prevent hereditary deafness. To comparison with some other studies that conducted in European and American countries.

Similar to many similar studies, there are some limitations for this study. First and the main limitation; it is a cross-sectional study and for the evaluation of the relationship between risk factors and outcome (SNHL) a stronger method such as cohort study is needed. Many of these risk factors were reported by mothers or other relevant and it is relatively unreliable.


  Acknowledgment Top


The authors would like to thank parents of children for their kindly cooperation.[28]

 
  References Top

1.Smith RJ, Bale JF Jr, White KR. Sensorineural hearing loss in children. Lancet 2005;365:879-90.  Back to cited text no. 1
    
2.Olusanya BO, Newton VE. Global burden of childhood hearing impairment and disease control priorities for developing countries. Lancet 2007;369:1314-7.  Back to cited text no. 2
    
3.Lee DS, Lee JS, Oh SH, Kim SK, Kim JW, Chung JK, et al. Cross-modal plasticity and cochlear implants. Nature 2001;409:149-50.  Back to cited text no. 3
    
4.Sharma A, Dorman MF, Kral A. The influence of a sensitive period on central auditory development in children with unilateral and bilateral cochlear implants. Hear Res 2005;203:134-43.  Back to cited text no. 4
    
5.Kral A, Hartmann R, Tillein J, Heid S, Klinke R. Delayed maturation and sensitive periods in the auditory cortex. Audiol Neurootol 2001;6:346-62.  Back to cited text no. 5
    
6.Al Khabori M. Causes of severe to profound deafness in Omani paediatric population. Int J Pediatr Otorhinolaryngol 2004;68:1307-13.  Back to cited text no. 6
    
7.Russ SA, Rickards F, Poulakis Z, Barker M, Saunders K, Wake M. Six year effectiveness of a population based two tier infant hearing screening programme. Arch Dis Child 2002;86:245-50.  Back to cited text no. 7
    
8.Levi H, Tell L, Cohen T. Sensorineural hearing loss in Jewish children born in Jerusalem. Int J Pediatr Otorhinolaryngol 2004;68:1245-50.  Back to cited text no. 8
    
9.Kral A, Hartmann R, Tillein J, Heid S, Klinke R. Delayed maturation and sensitive periods in the auditory cortex. Audiol Neurootol 2001;6:346-62.  Back to cited text no. 9
    
10.Saadat M, Ansari-Lari M, Farhud DD. Consanguineous marriage in Iran. Ann Hum Biol 2004;31:263-9.  Back to cited text no. 10
    
11.Akrami SM, Montazeri V, Shomali SR, Heshmat R, Larijani B. Is there a significant trend in prevalence of consanguineous marriage in Tehran? A review of three generations. J Genet Couns 2009;18:82-6.  Back to cited text no. 11
    
12.Olusanya BO, Newton VE. Global burden of childhood hearing impairment and disease control priorities for developing countries. Lancet 2007;369:1314-7.  Back to cited text no. 12
    
13.Zakzouk S, El-Sayed Y, Bafaqeeh SA. Consanguinity and hereditary hearing impairment among Saudi population. Ann Saudi Med 1993;13:447-50.  Back to cited text no. 13
    
14.Zakzouk S. Consanguinity and hearing impairment in developing countries: A custom to be discouraged. J Laryngol Otol 2002;116:811-6.  Back to cited text no. 14
    
15.Bener A, Eihakeem AA, Abdulhadi K. Is there any association between consanguinity and hearing loss. Int J Pediatr Otorhinolaryngol 2005;69:327-33.  Back to cited text no. 15
    
16.Elango S, Chand RP, Purohit GN. Childhood deafness in Malaysia. Int J Pediatr Otorhinolaryngol 1992;24:11-7.  Back to cited text no. 16
    
17.Dereköy FS. Etiology of deafness in Afyon School for the deaf in Turkey. Int J Pediatr Otorhinolaryngol 2000;55:125-31.  Back to cited text no. 17
    
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19.Reardon W. Genetic deafness. J Med Genet 1992;29:521-6.  Back to cited text no. 19
    
20.Minja BM. Aetiology of deafness among children at the Buguruni School for the Deaf in Dar es Salaam, Tanzania. Int J Pediatr Otorhinolaryngol 1998;42:225-31.  Back to cited text no. 20
    
21.Gray RF. Causes of deafness in schools for the deaf in Madras. Int J Pediatr Otorhinolaryngol 1989;18:97-106.  Back to cited text no. 21
    
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23.Egeli E, Ciçekci G, Silan F, Oztürk O, Harputluolu U, Onur A, et al. Etiology of deafness at the Yeditepe School for the deaf in Istanbul. Int J Pediatr Otorhinolaryngol 2003;67:467-71.  Back to cited text no. 23
    
24.Vartiainen E, Kemppinen P, Karjalainen S. Prevalence and etiology of bilateral sensorineural hearing impairment in a Finnish childhood population. Int J Pediatr Otorhinolaryngol 1997;41:175-85.  Back to cited text no. 24
    
25.Martin JA. Aetiological factors relating to childhood deafness in the European community. Audiology 1982;21:149-58.  Back to cited text no. 25
    
26.Janzen VD, Schaefer D. Etiology of deafness in Robarts School for the Deaf. J Otolaryngol 1984;13:47-8.  Back to cited text no. 26
    
27.Das VK. Aetiology of bilateral sensorineural hearing impairment in children: A 10 year study. Arch Dis Child 1996;74:8-12.  Back to cited text no. 27
    
28.Holborow C, Martinson FD, Anger N. A study of deafness in West Africa. International Journal of Pediatric Otorhinolaryngology 1982; 4: 107-132.  Back to cited text no. 28
    



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