Contribution of the N-acetyltransferase 2 polymorphism NAT2*6A to age-related hearing impairment.

BACKGROUND: Age-related hearing impairment (ARHI) is the most common sensory impairment in older people, affecting 50% of those aged 80 years. The proportion of older people is increasing in the general population, and as a consequence, the number of people affected with ARHI is growing. ARHI is a complex disorder, with both environmental and genetic factors contributing to the disease. The first studies to elucidate these genetic factors were recently performed, resulting in the identification of the first two susceptibility genes for ARHI, NAT2 and KCNQ4. METHODS: In the present study, the association between ARHI and polymorphisms in genes that contribute to the defence against reactive oxygen species, including GSTT1, GSTM1 and NAT2, was tested. Samples originated from seven different countries and were combined into two test population samples, the general European population and the Finnish population. Two distinct phenotypes for ARHI were studied, Z(low) and Z(high), representing hearing in the low and high frequencies, respectively. Statistical analysis was performed for single polymorphisms (GSTM1, GSTT1, NAT2*5A, NAT2*6A, and NAT2*7A), haplotypes, and gene-environment and gene-gene interactions. RESULTS: We found an association between ARHI and GSTT1 and GSTM1 in the Finnish population sample, and with NAT2*6A in the general European population sample. The latter finding replicates previously published data. CONCLUSION: As replication is considered the ultimate proof of true associations in the study of complex disorders, this study provides further support for the involvement of NAT2*6A in ARHI.

Familial aggregation of tinnitus: a European multicentre study.

INTRODUCTION AND AIM: Tinnitus is a common condition affecting approximately 20% of the older population. There is increasing evidence that changes in the central auditory system following cochlear malfunctioning are responsible for tinnitus. To date, few investigators have studied the influence of genetic factors on tinnitus. The present report investigates the presence of a familial effect in tinnitus subjects. METHODS: In a European multicentre study, 198 families were recruited in seven European countries. Each family had at least 3 siblings. Subjects were screened for causes of hearing loss other than presbyacusis by clinical examination and a questionnaire. The presence of tinnitus was evaluated with the question "Nowadays, do you ever get noises in your head or ear (tinnitus) which usually last longer than five minutes". Familial aggregation was tested using three methods: a mixed model approach, calculating familial correlations, and estimating the risk of a subject having tinnitus if the disorder is present in another family member. RESULTS: All methods demonstrated a significant familial effect for tinnitus. The effect persisted after correction for the effect of other risk factors such as hearing loss, gender and age. The size of the familial effect is smaller than that for age-related hearing impairment, with a familial correlation of 0.15. CONCLUSION: The presence of a familial effect for tinnitus opens the door to specific studies that can determine whether this effect is due to a shared familial environment or the involvement of genetic factors. Subsequent association studies may result in the identification of the factors responsible. In addition, more emphasis should be placed on the effect of role models in the treatment of tinnitus.

Longitudinal study of hearing impairment in children.

The aim of this study is to evaluate the frequency of progression in permanent childhood hearing impairment (PHI) and to relate potential specific factors to the eventual progression. A description is made of the true longitudinal hearing thresholds in four groups of children according to different observation periods and being part of a prospective pediatric audiological registry-based study established in 1989. At the time of data collection the registry included 1373 children born after 1/1-1970 with a PHI > 20 dB in either the right or the left ear at any pure tone frequency. The children were subdivided according to the following observation periods: 1-3 years (N=266), >3-5 years (N=148), >5-10 years (N=212) and >10 years (N=62). The differences from the first to the most recent audiometric thresholds were analysed for the right and left ears separately, at the pure tone frequencies 250, 500, 1000, 2000, 4000 and 8000 Hz, for the average of 500, 1000, 2000 and 4000 Hz, for the average of 2000 and 4000 Hz and for the average of 4000 and 8000 Hz. Those showing a progression >15 dB for the average across 500-4000 Hz were analysed for age at onset and aetiology of hearing impairment, showing that genetic factors are predominant in progressive PHI. It was also found that progression in PHI is most frequent in early childhood but found only in 5.7% after the age of 4 years.

Clinical trial of a low-cost, solar-powered hearing aid.

OBJECTIVE: In July 2001 the World Health Organization (WHO) launched their "Guidelines for hearing aids and services for developing countries". The objective of this study was to evaluate the clinical outcome of an analogue, low-cost, behind-the-ear hearing aid (BTE-HA) that met the minimum technical requirements outlined by the WHO. MATERIAL AND METHODS: A total of 25 subjects (17 males, 8 females; median age 74 years; range 50-86 years) were recruited among patients referred for audiological evaluation who consented to participate in the trial. All subjects had a hearing loss of < or = 60 dB HL at 2 kHz, were mobile and mentally unimpaired; 13 were experienced users of HAs, 3 suffered from mixed conductive/sensorineural hearing impairment (HI) and the remainder had pure sensorineural HI. Based on pure-tone, speech and impedance audiometry the BTE-HAs were fitted, using the National Acoustic Laboratories-R (NAL-R) prescription rule, 21 binaurally and 4 monaurally. All fittings were validated by insertion gain measurements, and the immediate benefit was measured by means of the speech recognition score in background noise (SRSN; signal:noise ratio = 10 dB) without and with the HA. After a 6-week trial period a structured interview based on the International Outcome Inventory for Hearing Aids (IOI-HAs) was performed. RESULTS: The results showed that the amplification of the HA deviated significantly from the NAL-R target at all frequencies, giving significantly more amplification at 500 and 1000 Hz despite maximum bass-cut, whenever relevant, and significantly less amplification as required at 2, 3 and 4 kHz. The median SRSN without HA was 48% (range 0-96%), which improved significantly to 80% (range 24-100%) with HA. The median individual difference in SRSN without and with HA was 20% (range 0-72%). The total IOI-HA score with the test HA was 4.1 (range 2.6-4.6), showing that it offered subjectively high satisfaction and reduction in limitations of activity. CONCLUSIONS: The low-cost HA: (i) provides benefit to the hearing-impaired person; (ii) offers poor amplification in the high frequencies; and (iii) gives subjective satisfaction similar to that for modern available HAs.

Provision of hearing aid services: a comparison between the Nordic countries and the United Kingdom.

About one in five adults has some form of hearing impairment. This paper reports on a survey which found significant variation in the provision of hearing aid services across Denmark, Finland, Norway, Sweden and the United Kingdom. Per capita expenditure levels were estimated to vary from under 3 euros in the UK to nearly 10 in Denmark and Norway. Annual figures for the number of people receiving at least one aid varied from around eight per 1,000 in the UK and Denmark to 2.2 in Finland. Over 50% of hearing aid users in Norway and Denmark are estimated to have bilateral aids, compared to under 15% in the UK. Estimates of the number of people who have a hearing aid in these countries are considerably lower than the number who have a hearing impairment. More research is needed to verify the true extent of these differences and their cause.

Is there a relationship between U-shaped audiograms and mutations in connexin 26?

The knowledge about gene mutations causing permanent hearing impairment (HI) is rapidly increasing, offering clinicians the possibility of analysing different gene mutations in relation to various phenotypes. This study examines a possible relationship between U-shaped audiograms and mutations in the GJB2-gene, coding for Connexin 26 (Cx 26). Thirty-eight subjects at a median age of 42 years, range 18-60 years with symmetric U-shaped audiograms classified as sensorineural were included in the genetic investigation. The gender distribution was 13 males and 25 females. No subjects had any indication of syndromic HI, and any possible exogenous factor that might cause HI was excluded. Three subjects had self-reported prelingual HI and 34 subjects had self-reported postlingual HI. Thirty-five subjects had one or more family members with HI. In 19 subjects the entire Cx 26 gene was examined, whereas 19 subjects were investigated for the 35delG mutation only. One female with mild HI and postlingual onset of the HI was heterogeneous for the L9OP-mutation in the Cx 26 gene. In all other subjects no mutations in the Cx 26 gene could be identified. Mutations of the Cx 26 gene are very rare among subjects exhibiting a U-shaped phenotype of the audiogram. However the majority of the investigated subjects (35/38) had a family history of HI and it seems therefore reasonable to ascribe U-shaped hearing deficit to genetic factors which has to be searched for in alternative gene mutations.

Some experiences with hearing disability/handicap and quality of life measures.

To achieve detailed information on the outcome of hearing rehabilitation in a clinical setting, measurements of hearing disability and hearing handicap have been introduced, and the present study describes the preliminary experiences with these measures in a series of hearing-impaired subjects referred for audiological evaluation. To outline hearing disability/hearing handicap (HD/HH), before continuation or initiation of treatment, the Gothenburg profile and a generic health-related quality of life--the SF-36 questionnaire--were used to evaluate any adverse effects resulting from hearing disorders. The Gothenburg profile and the SF-36 questionnaire were mailed to 634 subjects appointed for audiological examination with a request to complete the questionnaires at home. Three questions were enclosed concerning the capacity to complete the questionnaires, showing that 1.9 per cent were incapable of completing them, 17.5 per cent needed assistance, 43.5 per cent completed the questionnaires, and 37.1 per cent did not respond to them. Thus the response rate was only 55.5 per cent and, in addition, these responses were characterised by missing data. An arbitrary criterion of an average score per question of >3 for the averaged HD and HH items respectively was applied, resulting in 72.7 per cent indicating HD, whereas 30.3 per cent indicated HH according to the items in the profile. Significant differences in hearing levels were found between those experiencing HD and HH having a score >3 and those with a score <3. When analysing the general health status, general perception of health and social functioning, significantly lower scores were found for those experiencing HD/HH, whereas no significant differences were found between the total sample of hearing-impaired subjects and the age-matched population for these parameters. It is concluded that the present procedure cannot be implemented as a routine outcome measure in a clinical setting and alternative outcome measures should be considered.

A randomised controlled trial of screening for adult hearing loss during preventive health checks.

BACKGROUND: Prophylactic strategies to counter acquired hearing impairment may involve routine audiometric screening of asymptomatic working-age adults attending general practice for regular health checks. AIM: To evaluate the effect of adult hearing screening on subsequent noise exposure and hearing. DESIGN OF STUDY: A randomised controlled population-based study of health checks and health discussions in general practice. SETTING: The project was initiated in the district of Ebeltoft, Aarhus county, Denmark. METHOD: Intervention group participants' hearing thresholds were determined audiometrically at 0.5, 1, 2, 3, and 4 kHz in each ear. Participants were advised to get their ears checked if the average hearing loss exceeded 20 dB hearing level (dBHL) in either ear. Noise avoidance was emphasised when thresholds exceeded 25 dBHL bilaterally at 4 kHz. Follow-up included questionnaires and audiometry. RESULTS: Hearing loss was observed among 18.9% of the study sample at baseline. At the five-year follow-up we recorded no significant differences between the control and the intervention groups regarding subjective or objective hearing, or exposure to occupational noise. However, there was a tendency towards reduction in exposure to leisure noise among intervention participants (P = 0.045). Approximately 20% reported hearing problems; 16.5% reported tinnitus-related complaints; 0.8% used hearing aids; 35.0% reported frequent noise exposure; and occluding wax was suspected in 2.1%. CONCLUSION: Preventive health checks with audiometry did not significantly affect hearing, but leisure noise exposure tended to become less frequent. The poor effect may be ascribed to inadequate audiological counselling or a higher priority to other advice, e.g. on cardiovascular risk or lifestyle.

[Users' experiences with modern hearing aids. An audit]. / Brugernes erfaringer med moderne høreapparater. En audit.

INTRODUCTION: The aim of the study was to evaluate satisfaction with use and manipulation of hearing aids (HA), and to compare these parameters for analogue (A-HA), programmable (P-HA), and digital signal processing aids (DSP-HA). METHOD: An audit was made of data on users' experiences, as indicated in a questionnaire posted 3-4 months after the HA fitting. MATERIAL: Questionnaires were posted to 18,702 persons, who, during the period 1997-1999, had been provided with a HA at a median age of 77 years (range 18-98), 41.8% of whom were men, and 58.2% women. Responses were returned by 12,866 (68.8%), and, as there were no differences between the respondents and non-respondents with respect to age, gender, and distribution of HA type, the responses were considered representative. RESULTS: According to the replies, 71.5% were very satisfied/satisfied with their HA; 89% used the instrument daily/weekly, and 75% were able to manipulate the HA without problems. However, 10.7-12.7% said they never used the fitted HA. A significantly higher proportion were satisfied with A-HAs as compared to P-HAs and DSP-HAs, whereas there was no significant difference in use as a function of type. A significantly higher number of the users fitted with a DSP-HA could manipulate them, but 36.5% of these needed follow-up in contrast to 25.5% fitted with a P-HA, and 21.6% fitted with an A-HA. A significantly smaller proportion of the elderly were able to manipulate the HA. CONCLUSION: The users of modern HAs are satisfied with them, use them, and most are able to manipulate the HA without problems. The new technology has raised unrealistic expectations in the users, and the DSP-HAs account for larger costs to the national health services, because they are more expensive and the need for staff resources is greater.

Clinical study of hearing instruments: a cross-sectional longitudinal audit based on consumer experiences.

The objective of the present audit was to document improvements/changes in hearing instrument (HI) benefit in terms of use and satisfaction throughout the 1990s and compare the benefit in consumers fitted with analogue (A), programmable (P), and digital signal processing (DSP) HIs. The audit data are based on a questionnaire mailed to subjects fitted with HIs 3 to 4 months after the fitting, including questions concerning satisfaction with the HI, use of the HI, ability to manage the HI, and satisfaction with the overall services in the department. Information was obtained from 32,694 subjects (i.e., 71.2 per cent of those fitted with HIs throughout the last decade), with a median age at fitting of 78 years (range, 18-102), with a preponderance of females. No significant differences in age, gender distribution, and hearing instrument distribution were found between the respondents and non-respondents. The audit shows that there are no significant differences in any of the benefit parameters throughout the decade, irrespective of the introduction of P-HIs in 1995 and of the DSP-HIs in 1998. Thus, from the consumers' perspective, no changes have appeared in the last decade. A comparative analysis of the A-HIs, P-HIs, and DSP-HIs shows that among those provided with P-HIs and DSP-HIs, only 69.6 per cent (CI 68.1-71.0) and 65.5 per cent (CI 60.2-78.8), respectively, were very satisfied/satisfied with the HI, which is significantly less than the 73.5 per cent (CI 72.4-74.5) in those fitted with A-HIs. The daily/weekly use of all three types of HIs was similar. However, the group fitted with DSP-HIs was significantly less satisfied with the general services compared with those fitted with A-HIs and P-HIs, respectively. Based on these audit data, it is concluded that, according to the consumers, the outcome from HIs has not changed over the last decade, and a comparison between the traditional A-HIs with both P-HIs and DSP-HIs is in favour of the traditional A-HIs.

Two families with phenotypically different hereditary low frequency hearing impairment: longitudinal data and linkage analysis.

Two families with low frequency hearing impairment have been described previously. Family A (Danish) presented a sensorineural hearing impairment most pronounced for frequencies below 2 kHz and a pedigree typical for an autosomal dominant trait with complete penetrance (Königsmark type). Family B, originating from the Faroe Islands, showed conflicting audiological test results, making a valid classification impossible. The pedigree suggested autosomal dominant inheritance with incomplete penetrance. The objectives of the present study are to acquire longitudinal audiometric data, to clarify the mode of transmission, and to localize the mutant gene by reevaluation of the two families. The methods used are evaluation of the family history, audiological examination and linkage analysis. In family A, update of the pedigree fitted the assumption of an autosomal dominant mode of transmission. In six examined subjects audiological data were available from the previous study. The median progression over a 13-21-year period was 13.8 dB HL for the thresholds, averaged across 0.5, 1, 2 and 4 kHz and 17.5 dB HL for the thresholds, averaged across 2 and 4kHz. In family B, the probable mode of transmission is autosomal dominant with reduced penetrance. In this family no progression of the hearing impairment was found. Linkage analysis of family A showed a lod score of 3.53, indicating significant linkage to the loci DFNA6 and DFNA14 on chromosome 4, previously found to be involved in low frequency hearing impairment. Family B was not linked to the region on chromosome 4, further adding to the genetic heterogeneity in low frequency sensorineural hearing impairment.

Age-related hearing impairment and B vitamin status.

The aim of this study was to examine, in elderly subjects, a possible association between age-related hearing impairment and vitamin B12 or folic acid status. Ninety-one consecutive subjects with pure age-related hearing impairment, 35 males and 56 females, with a median age of 78 years, range 67-88 years, were included in the investigation. All subjects underwent a thorough evaluation, including pure-tone, speech and impedance audiometry. Blood samples were drawn for determination of B12, folic acid and homocysteine and analysed by routine laboratory measurements. No significant differences in the blood parameters as a function of gender could be demonstrated and no correlations were found between B12 or folic acid and hearing levels averaged across the range 0.5-4 kHz. A weak correlation between hearing levels and homocysteine (r = 0.03; correlation coefficient 0.004) was found; however, a comparison of the hearing levels between those with increased and normal homocysteine failed to show any significant differences. In addition, no association between B12 and the speech recognition score could be found. This investigation therefore fails to demonstrate any association between hearing level and vitamin B12 or folic acid in elderly subjects.

A five-year longitudinal study of hearing in a Danish rural population aged 31-50 years.

This paper aims to report changes in hearing sensitivity over five years in a rural population aged 31-50 years and to identify risk factors associated with hearing deterioration. The study is prospective and based on data from pure tone audiometry and questionnaires in the Ebeltoft Health Promotion Project in Denmark. A representative sample of 705 subjects had a complete follow-up, including audiometry. The median hearing deterioration was 2.5 dB at 3-4 kHz and 0 dB at 0.5-2 kHz. There was a high degree of individual variability in deterioration. The overall deterioration of hearing sensitivity of the population was largely predicted from the cross-sectional findings reported previously. In the analysis of risk factors, hearing deterioration was defined as an average deterioration 10 dB/5 years at 3-4 kHz in at least one ear. Deterioration was present in 23.5% of the sample. The 41-50-year-olds had a relative risk of deterioration of 1.32 (95% CI 1.01-1.73) compared with the 31-40-year-olds. Males had a relative risk of 1.35 (1.03-1.76) compared with females. The risk was not significantly elevated for a range of other possible risk factors confirmed by logistic regression analysis. In conclusion, deterioration in hearing sensitivity on population level can be predicted on the basis of cross-sectional findings. Hearing sensitivity deteriorated mainly at 3-4 kHz. The deterioration increased with age and was higher in males than in females. Other risk factors were not found. The present study does not support the hypothesis that hypertension or tobacco smoking is associated with deterioration in hearing.

Inherited sensorineural low-frequency hearing impairment: some aspects of phenotype and epidemiology.

This contribution forms part of the HEAR project. It describes some phenotypes of inherited low-frequency sensorineural hearing impairment (LFSHI) and estimates the prevalence of this inherited hearing impairment (HI) based on a clinical series. During a 10-year period (1987-1996), 418 subjects (134 males and 284 females), with a median age of 68 years (range 4-98), had been examined with LFSHI, defined as hearing loss most pronounced in the low frequencies (i.e., 250 and 500 Hz > 20 dB HL with better hearing, i.e., > or =15-dB difference at 1 and/or 2 and/or 4 kHz with an air-bone gap <15 dB for the average of 0.5, 1, and 2 kHz). The 418 subjects comprising 0.6 per cent of the total number of subjects examined (N=69,309) were subdivided into four categories: category I positive genetic subjects (N=69); category II, probably genetic (N=339); category III, uncertain genetic (N=6); and category IV, subjects with contradictory audiological findings (N=4). The phenotype in category I demonstrated a symmetrical LFSHI, with a pattern of progression showing a slow deterioration in the high frequencies (i.e., 2, 4, and 8 kHz as a function of age)--the progression comprising 40-45 dB. In the low frequencies (i.e., 250, 500, and 1,000 Hz), a deterioration of 15-25 dB could be demonstrated from the youngest to the oldest age group. In category II, a symmetrical LFSHI was found in 179 subjects, showing the same pattern of progression as in category I. However, in the age group 20-39 years, a significantly poorer hearing was found in the low frequencies compared to category I, implying that several phenotypes may be present in LFSHI. A subgroup (A) in category II exhibited normal hearing in one ear with LFSHI in the opposite ear with the same pattern of progression as in category I. Three other subgroups with LFSHI and flat/sloping audiogram in the opposite ear and asymmetrical LFSHI also showed the same type of progression in the ear with LFSHI as in category I. A prevalence of 0.18/1,000 (95 per cent CI 0.13-0.22) of LFSHI was estimated based on the background population with a fairly constant prevalence throughout life. It is concluded that inherited nonsyndromal LFSHI is a rare disease and that the many different phenotypes of LFSHI probably are associated with pronounced genetic heterogeneity.

Hearing screening--aspects of epidemiology and identification of hearing impaired children.

Mass screening of hearing in children is based on the concept of secondary prevention. In recognition of the importance of an early identification and intervention in children with congenital or early-acquired (i.e. neonatal period) hearing disability, numerous hearing screening programs have been introduced throughout the world. The devastating consequences of a congenital/early acquired hearing disability upon the speech, language, and social development of a child, and the estimated prevalence rates of at least 1-1.5/1000 live births of congenital permanent hearing impairment, represent an important health problem. The increase in the estimated prevalence of permanent hearing impairment in childhood, reaching at least 3.6-8.2% of live births at 5-9 years of age further emphasizes the importance of the problem. The delayed identification of children with congenital/early acquired hearing disability should result in the implementation of universal neonatal hearing screening, and the negative impact on the learning processes during school age from hearing impairment acquired throughout childhood seems to justify the introduction or maintenance of a hearing screening at school entrance. Implementation of efficient hearing screening programs throughout the neonatal period, infancy, or childhood should result in secondary prevention of this important health problem.

Clinical otosclerosis, prevalence estimates and spontaneous progress.

This retrospective study was performed in order to estimate the prevalence of clinical otosclerosis as a function of age and gender, characterize the hearing level in otosclerosis and describe the spontaneous progress of the disease as a function of age. Clinically based samples were obtained from an audiological department, including 556 subjects: n = 166 (30%) males and n = 390 (70%) females with a median age of 75 years (range 22-95 years) at the time of examination. A subdivision of the sample into 3 age-bands, 20-39 years (n = 39), 40-59 years (n = 78) and > or = 60 years (n = 439), was performed. The overall prevalence estimate of clinical otosclerosis in the area in question was 1.41/1,000 [95% confidence interval (CI) = 1.3-1.5/1,000] with an estimate of 0.9/1,000 (95% CI = 0.8-1.0/1,000) in males and 1.85/1,000 (95% CI = 1.7-2.1/1,000) in females, with an increase in the prevalence as a function of age from 0.22/1,000 (95% CI = 0.15-0.29/1,000) to 3.53/1,000 (95% CI = 3.2-3.86/1,000) in the elderly. The estimates should be considered underestimates, as not all clinical otosclerosis in the area was included. No significant differences in the better and worse ear hearing levels averaged across 0.5-4 kHz (BEHL/WEHL 0.5-4 kHz) were found as a function of gender, and in general the impairment in the BEHL 0.5-4 kHz was fairly moderate until the age of 60 years. In ears previously subjected to surgery a significantly better hearing level of median 63 dB (range 24-119 dB) was found than in the no-surgery ears, with a median hearing level of 71 dB (range 5-120 dB). An estimate of the progress showed an increment in the hearing level in the elderly > or = 60 years of 30 dB over 30 years in non-operated ears, fairly similar to the 40 dB progress in operated ears. It was concluded that a significantly higher prevalence of clinical otosclerosis is present in females than in males, that the overall hearing level in otosclerosis is fairly moderate until the age of 60 years, and that previously operated ears have significantly better hearing than non-operated ears.

Prevalence of hereditary hearing impairment in adults.

This contribution, part of an EU-Concerted Action on the genetics of hearing impairment (H.E.A.R.), describes the preliminary estimated prevalence of hereditary hearing impairment based on retrospective data from a clinical series. Of 27,692 subjects examined in the period 1987-91, we sampled 1265 suffering from unilateral or bilateral hereditary hearing impairment, which is roughly 5% of those examined (n = 384 (31%) male; n = 881 (69%) female). Median age of the subjects is 70 years (range 22-98). Subdividing them into 10-year birth cohorts and applying the local annual population statistics, the prevalence of an overall age-related hereditary hearing impairment was roughly estimated to be 3.2/1000, reflecting prevalences as a function of age from 0.8 to 9.4/1000--prevalence in females being significantly more than in males (4.1/1000 and 2.1/1000, respectively). Overall, a moderate hearing impairment of median 51 dB in the better hearing ear was found, averaged across 0.5-4 kHz, this being fairly constant up to the age of 60, when a significant reduction in hearing sensitivity developed. No significant differences are present as a function of gender, except for the birth cohorts 1910-19 and 1920-29. The most frequent type of hereditary hearing impairment in this sample is otosclerosis, comprising 2% of the total clinical series with a rough population prevalence estimate of 1.4/1000. It is concluded that the established database may be of importance in the aggregation of very rare diseases, and for providing the inspiration for future prospective population studies, resulting in knowledge on the epidemiology of hereditary hearing impairment in adults.

The need for universal neonatal hearing screening--some aspects of epidemiology and identification.

The devastating consequences of a congenital/early-acquired hearing disability on the speech language and social development of a child and the estimated prevalence rates of at least 1-1.5/1000 live births of congenital permanent hearing impairment are important health problems. Universal neonatal hearing screening programs have provided the opportunity to detect neonates with permanent congenital hearing loss, and thus initiate auditory rehabilitation before the age of 3 mo. Universal neonatal hearing screening represents secondary prevention of hearing impairment/deafness, and the world-wide documented delayed identification of children with congenital/early-acquired hearing impairment will no doubt be improved with the implementation of universal neonatal hearing screening programs.