Etiology Of Hearing Impairment Research Articles

A Consolidated Understanding of the Contribution of Redox Dysregulation in the Development of Hearing Impairment.

The etiology of hearing impairment is multifactorial, with contributions from both genetic and environmental factors. Although genetic studies have yielded valuable insights into the development and function of the auditory system, the contribution of gene products and their interaction with alternate environmental factors for the maintenance and development of auditory function requires further elaboration. In this review, we provide an overview of the current knowledge on the role of redox dysregulation as the converging factor between genetic and environmental factor-dependent development of hearing loss, with a focus on understanding the interaction of oxidative stress with the physical components of the peripheral auditory system in auditory disfunction. The potential involvement of molecular factors linked to auditory function in driving redox imbalance is an important promoter of the development of hearing loss over time.

Hearing Outcome and Predictors after Implanting Bone Conduction or Middle Ear Implants in Ears with Refractory Otitis Media.

Bone conduction implants (BCIs) and middle ear implants (MEIs) are promising options for individuals with persistent chronic inflammation of the middle or outer ear. However, the structure of the middle ear is often altered in patients who undergo mastoidectomy or posterior wall removal for refractory otitis media, leaving uncertainty regarding the efficacy of hearing devices. Only a few studies have examined auditory outcomes based on the etiology of hearing impairment. We investigated hearing outcomes, including speech audiometry, in patients who underwent implantation after surgery for refractory otitis media. Our findings indicated that patients who received BCIs or MEIs achieved favorable hearing outcomes. Furthermore, a correlation was observed between the preoperative bone-conduction threshold at 1 kHz in the better ear and the sound-field threshold at 1 kHz with BCIs, whereas no correlation was observed between the preoperative bone-conduction threshold and the sound-field threshold with MEIs. This study highlights the positive impact of BCIs and MEIs in patients who undergo implantation after surgery for refractory otitis media. Additionally, our study identified parameters that predict postoperative efficacy.

ADAMTS1, MPDZ, MVD, and SEZ6: candidate genes for autosomal recessive nonsyndromic hearing impairment

Hearing impairment (HI) is a common disorder of sensorineural function with a highly heterogeneous genetic background. Although substantial progress has been made in the understanding of the genetic etiology of hereditary HI, many genes implicated in HI remain undiscovered. Via exome and Sanger sequencing of DNA samples obtained from consanguineous Pakistani families that segregate profound prelingual sensorineural HI, we identified rare homozygous missense variants in four genes (ADAMTS1, MPDZ, MVD, and SEZ6) that are likely the underlying cause of HI. Linkage analysis provided statistical evidence that these variants are associated with autosomal recessive nonsyndromic HI. In silico analysis of the mutant proteins encoded by these genes predicted structural, conformational or interaction changes. RNAseq data analysis revealed expression of these genes in the sensory epithelium of the mouse inner ear during embryonic, postnatal, and adult stages. Immunohistochemistry of the mouse cochlear tissue, further confirmed the expression of ADAMTS1, SEZ6, and MPDZ in the neurosensory hair cells of the organ of Corti, while MVD expression was more prominent in the spiral ganglion cells. Overall, supported by in silico mutant protein analysis, animal models, linkage analysis, and spatiotemporal expression profiling in the mouse inner ear, we propose four new candidate genes for HI and expand our understanding of the etiology of HI.

Lyme Borreliosis Associated with Sensorineural Hearing Loss: A Case Report

Background: Lyme borreliosis is a tick-borne infection caused by Borrelia species. It has a geographic distribution that makes it more frequent in certain regions like like North America and Europe. It manifests in a wide range of symptoms but is often under-investigated in patients presenting with sensorineural hearing loss (SNHL). Case Report: In this report, we describe a case presenting with SNHL as a manifestation of neuroborreliosis in a female adult patient suffering from Lyme disease, with multiple metachronous symptoms, including arthritis and seizures. Lyme borreliosis (LB) was clinically diagnosed and supported by positive serologic tests, along with Babesiosis. The patient was treated with intravenous (IV) ceftriaxone and azithromycin, in addition to oral atovaquone. Improvement after 4 weeks of IV ceftriaxone was noted in all aspects, including SNHL and arthritis. Conclusion: LB is a possible, but rare, etiology of hearing impairment. It has been documented that if treatment is initiated early, improvement and even complete recovery are possible. Hence, in a patient presenting with SNHL and a high index of suspicion for LB, assessment for LB is warranted.

Retrospective study of cochlear implantations at a single facility focusing on postoperative complications

ObjectiveAlthough cochlear implantation (CI) is a relatively safe operation, postoperative complications sometimes occur. We reviewed the frequency and severity of complications of CI at our hospital. We compared our results with previously reported complications and considered measures to improve patient outcomes. MethodsThis retrospective study examined the medical records of 70 patients who received CI between March 2005 and December 2018. We collected the following data: age at the time of the first surgery, etiology of hearing impairment, date of implantation, type of implanted devices, and complications. Surgical complications were divided by time into perioperative, early, and late, and by severity into major or minor. ResultsRecords of 38 adults and 32 children were analyzed. Bilateral CI was performed in 16 patients, 8 of whom were sequential, and unilateral CI was performed in 54 patients. The total number of operations was 78 for 86 CI. Complications were observed in 15 of 78 operations (19%), and the rates of minor and major complications were 15% and 4%, respectively. Complication rates were 21% (8/39) for children and 10% (4/39) for adults. All of the perioperative and early complications were minor. There were three major complications, all of which were infections presenting with mastoiditis and subcutaneous or subperiosteal abscesses. One case required reimplantation twice because of recurrent mastoiditis and temporal abscess. ConclusionsThere was no significant difference in the incidence of complications between children and adults, but all major complications were infection in pediatric cases. Careful attention is needed to prevent postoperative infection.

Molecular Mechanisms and Biological Functions of Autophagy for Genetics of Hearing Impairment.

The etiology of hearing impairment following cochlear damage can be caused by many factors, including congenital or acquired onset, ototoxic drugs, noise exposure, and aging. Regardless of the many different etiologies, a common pathologic change is auditory cell death. It may be difficult to explain hearing impairment only from the aspect of cell death including apoptosis, necrosis, or necroptosis because the level of hearing loss varies widely. Therefore, we focused on autophagy as an intracellular phenomenon functionally competing with cell death. Autophagy is a dynamic lysosomal degradation and recycling system in the eukaryotic cell, mandatory for controlling the balance between cell survival and cell death induced by cellular stress, and maintaining homeostasis of postmitotic cells, including hair cells (HCs) and spiral ganglion neurons (SGNs) in the inner ear. Autophagy is considered a candidate for the auditory cell fate decision factor, whereas autophagy deficiency could be one of major causes of hearing impairment. In this paper, we review the molecular mechanisms and biologic functions of autophagy in the auditory system and discuss the latest research concerning autophagy-related genes and sensorineural hearing loss to gain insight into the role of autophagic mechanisms in inner-ear disorders.

Анализ мутационного спектра гена SLC26A4 и его вклада в этиологию наследуемой потери слуха у коренного населения Южной Сибири

Мутации в гене SLC26A4 являются частой причиной потери слуха во многих регионах мира. В работе приводятся результаты молекулярно-генетического анализа (с использованием секвенирования по Сэнгеру) последовательности гена SLC26A4, впервые проведенного в выборке пациентов с потерей слуха неустановленной этиологии (n=232) из Республик Тыва и Алтай. Установлены контрастные различия патогенетического вклада мутаций в гене SLC26A4 в этиологию нарушения слуха у коренных жителей этих географически близких регионов: 28,2% - для тувинцев и 4,3% - для алтайцев. Выявлены как уже известные, так и новые патогенные варианты, а также широкий спектр полиморфных вариантов гена SLC26A4. Mutations in the SLC26A4 gene are a common cause of hearing loss in many regions of the world. This paper presents the results of molecular genetic analysis (by Sanger sequencing) of the SLC26A4 sequence, first performed in the sample of patients with hearing loss of unknown etiology (n=232) from the Tyva Republic and the Altai Republic. Contrast differences of the pathogenic contribution of SLC26A4 mutations to the etiology of hearing impairment were revealed in the indigenous peoples of these geographically close regions: 28.2% for Tuvinians and 4.3% for Altaians. Both known and novel pathogenic variants as well as a wide range of polymorphic variants were found in the SLC26A4 gene sequence.

Hearing Impairment Overview in Africa: the Case of Cameroon.

The incidence of hearing impairment (HI) is higher in low- and middle-income countries when compared to high-income countries. There is therefore a necessity to estimate the burden of this condition in developing world. The aim of our study was to use a systematic approach to provide summarized data on the prevalence, etiologies, clinical patterns and genetics of HI in Cameroon. We searched PubMed, Scopus, African Journals Online, AFROLIB and African Index Medicus to identify relevant studies on HI in Cameroon, published from inception to 31 October, 2019, with no language restrictions. Reference lists of included studies were also scrutinized, and data were summarized narratively. This study is registered with PROSPERO, number CRD42019142788. We screened 333 records, of which 17 studies were finally included in the review. The prevalence of HI in Cameroon ranges from 0.9% to 3.6% in population-based studies and increases with age. Environmental factors contribute to 52.6% to 62.2% of HI cases, with meningitis, impacted wax and age-related disorder being the most common ones. Hereditary HI comprises 0.8% to 14.8% of all cases. In 32.6% to 37% of HI cases, the origin remains unknown. Non-syndromic hearing impairment (NSHI) is the most frequent clinical entity and accounts for 86.1% to 92.5% of cases of HI of genetic origin. Waardenburg and Usher syndromes account for 50% to 57.14% and 8.9% to 42.9% of genetic syndromic cases, respectively. No pathogenic mutation was described in GJB6 gene, and the prevalence of pathogenic mutations in GJB2 gene ranged from 0% to 0.5%. The prevalence of pathogenic mutations in other known NSHI genes was <10% in Cameroonian probands. Environmental factors are the leading etiology of HI in Cameroon, and mutations in most important HI genes are infrequent in Cameroon. Whole genome sequencing therefore appears as the most effective way to identify variants associated with HI in Cameroon and sub-Saharan Africa in general.

Prevalence of hearing impairment among primary school children in the Kilimanjaro region within Tanzania

IntroductionHearing impairment is becoming a public health concern and a widespread problem. The World Health Organization estimates that globally there are about 466 million people with hearing impairment, of which 34 million represent children. We examined the prevalence and etiology of hearing impairment among primary school children in the Kilimanjaro region within Tanzania. MethodA cross-sectional study of primary school children aged 6–17 was conducted to determine the prevalence of hearing impairment. Tanzanian primary school children were screened for hearing loss and an otoscopy was performed on those who failed the screening. ResultsThere were 403 children screened from three schools in rural areas of Tanzania. The prevalence of hearing loss was found to be 7.1%, 10.8% and 16.7% in the different schools. Cerumen was proven to be the most common possible cause of hearing impairment. Other possible causes of hearing impairment were found to be (in descending order) otitis (all types), no abnormalities, and perforation of the tympanic membrane. ConclusionsThese results show a need for better identification of hearing impairment in school-going children and implementation of prevention and treatment options in Tanzania and other developing countries. This can further improve children's potential for language development, communication and academic achievement.

Mutation Analysis Using Multiplex Ligation-Dependent Probe Amplification in Consanguineous Families in South India with a Child with Profound Hearing Impairment.

Consanguineous marriage, a common practice in South India, increase the incidence of autosomal recessive diseases such as nonsyndromic hearing loss (NSHL) in offspring. This trend was noted in the children with hearing impairment (HI) who received cochlear implants (CI) at our University hospital in Porur, Chennai, India. To ascertain the genetic etiology of HI in these patients, we performed multiplex ligation-dependent probe amplification (MLPA) analysis. A total of 25 families who had a child with NSHL were included in the study. MLPA screening of GJB2, GJB6, and GJB3 was performed for all the recruited individuals. The pathogenic p.W24X* mutation of GJB2 was detected in 2 patients; both of their parents were heterozygous carriers. Both families had a second-degree consanguineous marriage. This study has important implications for molecular-diagnosis strategy and genetic counseling for families with HI in South India.

Mutation spectrum and hotspots of the common deafness genes in 314 patients with nonsyndromic hearing loss in Heze area, China

Background: Although, half of the childhood deafness is genetically related, the molecular etiology of hearing impairment has not been demonstrated explicitly. In addition, the mutation spectrums of deafness genes vary among different areas and ethnics.Objectives: To know more about the mutation spectrums of deafness genes in China, we tested the mutations of three common deafness genes (GJB2, SLC26A4, and mtDNA12SrRNA) in a particular deafness population from Heze area.Materials and methods: SNPscan technology was utilized to perform mutation screening for these three common deafness genes in 314 nonsyndromic deaf patients from Heze area.Results: 38.21% (120/314) of these 314 patients with nonsyndromic hearing loss from Heze area were related to the genetic defects in these three deafness genes, including 20.06% (63/314) for GJB2, 15.29% (48/314) for SLC26A4, and 2.87% (9/314) for mtDNA12SrRNA. Furthermore, the mutation hotspots in three deaf genes were GJB2 235delC, SLC26A4 c.919-2A > G, and mtDNA12SrRNA 1555A > G, respectively, distinct from hotspots reported in other regions worldwide.Conclusion: Our results disclosed a special and unique mutation spectrum of these three common deaf genes in Heze deaf population.

Language outcome in children with congenital hearing impairment: The influence of etiology

ObjectivesTo investigate the possible association between the etiology of hearing impairment (HI) and language outcome in children with congenital HI after an early medical-technical intervention and three years of AVT. MethodsA retrospective, two-center study was conducted of 53 patients who were divided in four categories of etiology (degeneratio labyrinthi acustici (DLA) congenita hereditaria, DLA congenita non specificata, DLA congenita postinfectiosa and auditory neuropathy). Language outcome was assessed by examining receptive vocabulary (Peabody Picture Vocabulary Test, PPVT-4), receptive language (Reynell test) and productive language (the Danish ‘Viborgmaterialet’). All tests were conducted 1, 2 and 3 years after the children received their hearing device. Test scores were calculated from the child's chronological age. Analysis of possible associations was performed using Fisher's exact test and McNemar's test was conducted to examine possible differences between each year of testing for every speech-language test. Subsequently, univariate analyses were performed to search for other possible covariates associated with language outcome. ResultsNo significant associations were found between the etiology of the HI and the language outcome of children with HI after 1 year of AVT (PPVT, p = 0,234; Reynell, p = 0,845; Viborgmaterialet, p = 0,667), neither after 2 years of AVT (PPVT, p = 0,228; Reynell, p = 0,172; Viborgmaterialet, p = 0,659) nor after 3 years of AVT (PPVT, p = 0,102; Reynell, p = 0,512 Viborgmaterialet, p = 0,580). Some significant associations were found between language outcome and the type of hearing device and between language outcome and additional disabilities, however no strong evidence was found. ConclusionMost children with congenital HI developed a comparable level of speech and language regardless of the etiology of their HI. This study highlights the interest of further research using objective assessments techniques in a larger and more homogeneous population. If the findings from this study will be confirmed in future studies, this will have a clinical and societal impact regarding the diagnostics of HI.

Marital Structure, Genetic Fitness, and the GJB2 Gene Mutations among Deaf People in Yakutia (Eastern Siberia, Russia)

Autosomal recessive deafness type 1A (DFNB1A) caused by mutations in the GJB2 gene (Cx26) is the main cause of nonsyndromic hearing impairment in many populations worldwide. It is considered that widespread prevalence of DFNB1A can be due to the long tradition of intermarriages between deaf people (assortative marriages) combined with their increased social adaptation and genetic fitness after widespread introduction of sign language. For the first time, the data on mating structure and reproduction of deaf people living in Yakutia (Eastern Siberia, Russia) are presented in comparison with contribution of the GJB2 gene mutations to the etiology of hearing impairment. The relative fertility of deaf people compared to their hearing siblings is 0.78 (mean number of children 1.76 ± 0.10 and 2.24 ± 0.09 to deaf and their hearing siblings, respectively, p = 0.0018). The rate of assortative marriages among deaf people is 77.1% (81 of 105 marriages). Biallelic mutations in the GJB2 gene were found in 42.2% (43 of 102) of examined deaf people, which corresponded to diagnosis DFNB1A for these patients. A comparison of deaf marital partners by GJB2 status revealed a proportion of noncomplementary marriages (24%) in which hearing loss in both partners was caused by the presence of biallelic GJB2 gene mutations resulting in the birth of only deaf children in such couples. Thus, the set of obtained data including a relatively high genetic fitness (expressed as relative fertility) of deaf people in Yakutia in combination with a high rate of assortative marriages among them and high incidence of DFNB1A indicates a possible weakening of selection against such trait as “deafness” and a possible increase in the frequency of GJB2 mutant alleles in subsequent generations.

Public Health Burden of Hearing Impairment and the Promise of Genomics and Environmental Research: A Case Study in Ghana, Africa.

Hearing impairment (HI) is one of the most disabling conditions of major global health burden that contributes adversely to the social and economic development of a country, if not managed properly. A proper assessment of the nationwide burden and etiology of HI is instrumental in the prevention, treatment, and management of the condition. This article sought to perform an expert review of HI in Ghana to determine the present knowledge of its burden and possible causes of the condition. A literature search was conducted in PubMed using the following keywords: "hearing loss" OR "hearing impairment" OR "deafness" AND "Ghana." The literature was scanned until July 20, 2017, with specific inclusion of targeted landmark and background articles on HI. From the search, 18 of out 5869 articles were selected and considered for the review. The results of the search indicated that there were no extensive studies to determine the national burden of HI in Ghana. However, the few studies assessed suggested that the disease is either acquired or inherited. The burden of acquired HI was higher in adults than children, women than men, and people working in a noisy environment. Regarding the genetic cause, specific founder mutations in GJB2 gene (R143W, L79P, V178A, R184Q, A197S, I203K, and L214P) was the only identified genetic cause of HI in Ghana, but the other HI genes were not investigated. There has been some modest effort to study HI in Ghana, but comprehensive studies on the genetic and environmental etiologies (using the "multi-OMICS" approaches), classification, and burden of HI on Ghana are needed.

Hearing Impairment Prevalence and Associated Risk Factors in the Hispanic Community Health Study/Study of Latinos.

Hearing impairment is common in adults, but few studies have addressed it in the US Hispanic/Latino population. To determine the prevalence of hearing impairment among US Hispanic/Latino adults of diverse backgrounds and determine associations with potential risk factors. The Hispanic Community Health Study/Study of Latinos (HCHS/SOL) is a population-based sample of Hispanics/Latinos in four US communities (Bronx, New York; Chicago, Illinois; Miami, Florida; and San Diego, California). Examinations were conducted from 2008 through 2011. The HCHS/SOL examined 16,415 self-identified Hispanic/Latino persons aged 18 to 74 years recruited from randomly selected households using a stratified 2-stage area probability sample design based on census block groups and households within block groups. Hearing thresholds were measured by pure-tone audiometry. Hearing impairment was defined as a pure-tone average (PTA) of thresholds at 0.5, 1, 2, and 4 kHz greater than 25 dB hearing level. Bilateral hearing impairment required a PTA greater than 25 dB hearing level in both ears. Multivariable analyses included adjustments for sociodemographic and lifestyle variables, body mass index, and medical conditions. The prevalence of hearing impairment was 15.06% (SE, 0.44%) overall, and 8.24% (SE, 0.33%) had bilateral hearing impairment. The prevalence of hearing impairment was higher among people 45 years and older, ranging by Hispanic/Latino background from 29.35% to 41.20% among men and 17.89% to 32.11% among women. The multivariable-adjusted odds of hearing impairment was greater for participants of Puerto Rican background compared with Mexican background (odds ratio [OR], 1.57 [95% CI, 1.10-2.25]). The odds of hearing impairment were lower with more education (OR, 0.71 [95% CI, 0.59-0.86] for at least high school) and higher income (OR, 0.58 [95% CI, 0.36-0.92] for >$75,000 vs ≤$10,000). Noise exposure (OR, 1.35 [95% CI, 1.07-1.70]), diabetes (OR, 1.57 [95% CI, 1.27-1.94]), and prediabetes (OR, 1.37 [95% CI, 1.12-1.67]) were associated with hearing impairment. Hearing impairment is a common problem for older Hispanics/Latinos in these communities and is associated with socioeconomic factors, noise exposure, and abnormal glucose metabolism. Longitudinal studies are needed to determine whether these factors are involved in the etiology of hearing impairment and to identify ways to prevent or delay age-related changes in hearing.

Childhood hearing impairment in northern Finland, etiology and additional disabilities

ObjectivesThe purpose of this study was to determine the prevalence and etiology of hearing impairment (HI) in Finnish children and to evaluate the frequency and type of additional disabilities among children with HI. MethodsSubjects consisted of 214 children with mild to profound HI ascertained until the age of 10 years. They belonged to the birth cohort spanning the years 1993–2002 in northern Finland. The clinical data were collected from the electronic patient records of the Oulu University Hospital. Age at ascertainment, degree and type of HI and audiogram configuration were determined. Risk factors and etiology of HI and co-existing disabilities were recorded. ResultsThe prevalence of childhood HI was 2.3/1000 live births (95% CI; 2.0, 2.7). The etiology of HI was genetic in 47.2%, acquired in 16.4% and unknown in 36.4% children. Among the 214 children with HI, 101 (47.2%) had other minor or major disabilities. The frequency of additional disabilities did not differ between children with mild HI and those with moderate or severe HI (p=0.78). Additional disabilities were more common (65.7%) in children with acquired HI than in children with genetic or unknown HI (43.6%) (p=0.035). ConclusionThe prevalence of childhood HI has remained unchanged in northern Finland as compared to previous studies. Genetic causes were the most common (47%) etiology of childhood HI. Among acquired causes of HI, perinatal risk factors were more common than previously. The frequency of additional disabilities was similar among children with different degrees of HI. Because almost 40% of children had one or more additional disabilities affecting development or learning, it is important to take them into consideration in rehabilitation.

Etiology of Hearing Impairment in Children and Adolescents of a Reference Center APADA in the city of Salvador, state of Bahia

SummaryHearing represents the main source for acquisition of language and speaking skills in childhood. In the first months of life, the hearing impaired child is deprived of sound stimulation in the most important period of development, and consequently, might present emotional, social and linguistic disorders. Therefore, it is of utmost relevance to learn about the main etiological factors that cause the auditory damage to trace a reliable nosological profile, and to take the appropriate measures to prevent and guide the family on the repercussions of hearing impairment in childhood.AimTo characterize the etiology profile of hearing impairment in a reference center for hearing impaired children and adolescents.MethodologyWe performed interviews, speech and hearing screening and analyses of medical charts of 87 hearing impaired children that were part of Associação de Pais e Amigos dos Deficientes Auditivos do Estado da Bahia (APADA-BA), trying to define etiology, gender distribution, age at diagnosis, level of hearing loss, age at hearing aid fitting, and rehabilitation.ResultsAmong the 87 children and adolescents who had undergone speech and hearing screening, we select a sample of 53 subjects, whose parents had come for three sessions of anamnesis and assessment. The main responsible etiological factor for hearing loss in the evaluated population was maternal rubella, amounting to 32% of the cases of deafness, followed by pyogenic meningitis with 20%, idiopathic cause with 15%, prematurity with 9%, heredity (deaf father or mother) and neonatal jaundice, which also presented 6% incidence; chronic otitis media represented 4%, use of misoprostol in the gestation, measles, ototoxicity and mumps, each factor with 2%.ConclusionThe present study demonstrated the heterogeneity of factors that cause hearing impairment, and the two main causes (rubella and pyogenic meningitis) still present high incidence in the studied population. We believe that preventive measures must be taken, especially in the prophylaxis of maternal rubella and extended vaccination of neonates and infants against bacterial meningitis.

An epidemiological study on children with syndromic hearing loss

To study the epidemiological factors in children with syndromic hearing loss. Interview based prospective study. Govt. ENT Hospital, AYJNIHH, NIMH-SEC, and Schools for the Deaf-in Hyderabad and SecunderabadPatients: Children aged below 14 years, with hearing loss, their parents/guardians. The study revealed type and degree of hearing impairment. In high risk groups genetic counseling was offered. Epidemiological studies were carried out in 743 children below 14 years with hearing impairment and 138 (18.57%) were found to have syndromic deafness. Majority of the children with hearing loss have an association of ocular abnormality (22.46%, n=31) followed by skeletal anomalies 14.49% (n=20) and dental anomalies (10.86%). We observed 24 cases (3.21%) with genetically well recognized syndromes. Data is generated on epidemiological and etiology of Hearing Impairment. Hearing Impairment is due to both environmental and genetic causes. Environmental factors in 17 (13.77%), genetically inherited 21 cases (15.22%) and the cause is not known in the remaining cases. Such a data is required in order to offer genetic counseling to reduce the genetic burden.

Prevalence and etiology of unilateral sensorineural hearing impairment in a Finnish childhood population

A retrospective study was undertaken on the prevalence and etiology of unilateral sensorineural hearing impairment (>25 dB at 0.5–4 kHz, including mixed hearing impairments with bone conduction thresholds≥25 dB) among children born between 1972 and 1986 in a province of eastern Finland. Only patients who had been diagnosed before the age of 10 years were included. A total of 84 children with such an unilateral hearing loss were identified, with prevalence of 1.7 per 1000 live births. A significant decline from the prevalence of 2.2 per 1000 in the 1970s to the prevalence of 1.2 per 1000 in the 1980s was observed, which was mainly due to the disappearance of hearing losses caused by mumps and measles in the 1980s and the decrease in cases attributed to otitis media. In agreement with some previous studies, a considerable male predominance was present. Thirty-five percent of the hearing losses were profound (>95 dB) and 15% were severe (71–95 dB). Etiology of the hearing impairment was estimated as genetic in 2%, congenital non-genetic in 12%, delayed-onset non-genetic in 35% and remained unknown in 51%.

Incidence, Prevalence and Etiology of Hearing Impairment in Children in the County of VÄsterbotten, Sweden

During the period 1964-83, 63,463 children were born in the county of Västerbotten, Sweden. Of these children, 160 had a hearing impairment greater than or equal to 30 dB HL mean hearing loss for the frequencies 0.5, 1.0 and 2.0 kHz in the better-hearing ear. The mean annual incidence of hearing impairment was 2.5 per 1,000 and the prevalence was 2.6 per 1,000. Hereditary factors were present in 46% and no etiology could be established in 34% of the cases. The incidence of hearing impairment was greater than has been presented in studies from other areas in Europe.