Sylvia J. W. Kunst

Occupational Noise, Smoking, and a High Body Mass Index are Risk Factors for Age-related Hearing Impairment and Moderate Alcohol Consumption is Protective: A European Population-based Multicenter Study

A multicenter study was set up to elucidate the environmental and medical risk factors contributing to age-related hearing impairment (ARHI). Nine subsamples, collected by nine audiological centers across Europe, added up to a total of 4,083 subjects between 53 and 67 years. Audiometric data (pure-tone average [PTA]) were collected and the participants filled out a questionnaire on environmental risk factors and medical history. People with a history of disease that could affect hearing were excluded. PTAs were adjusted for age and sex and tested for association with exposure to risk factors. Noise exposure was associated with a significant loss of hearing at high sound frequencies (>1 kHz). Smoking significantly increased high-frequency hearing loss, and the effect was dose-dependent. The effect of smoking remained significant when accounting for cardiovascular disease events. Taller people had better hearing on average with a more pronounced effect at low sound frequencies (<2 kHz). A high body mass index (BMI) correlated with hearing loss across the frequency range tested. Moderate alcohol consumption was inversely correlated with hearing loss. Significant associations were found in the high as well as in the low frequencies. The results suggest that a healthy lifestyle can protect against age-related hearing impairment.

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, Zlow and Zhigh, 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.

Bone-anchored hearing aid system application for unilateral congenital conductive hearing impairment: audiometric results.

Objective: To study the audiologic outcome of bone-anchored hearing aid (BAHA) application in patients with congenital unilateral conductive hearing impairment. Study Design: Prospective audiometric evaluation on 20 patients. Setting: Tertiary referral center. Patients: The experimental group comprised 20 consecutive patients with congenital unilateral conductive hearing impairment, with a mean air-bone gap of 50 dB. Methods: Aided and unaided hearing was assessed using sound localization and speech recognition-in-noise tests. Results: Aided hearing thresholds and aided speech perception thresholds were measured to verify the effect of the BAHA system on the hearing acuity. All patients fulfilled the criteria that the aided speech reception thresholds or the mean aided sound field thresholds were 25 dB or better in the aided situation. Most patients were still using the BAHA almost every day. Sound localization scores varied widely in the unaided and aided situations. Many patients showed unexpectedly good unaided performance. However, nonsignificant improvements of 3.0 (500 Hz) and 6.9 degrees (3,000 Hz) were observed in favor of the BAHA. Speech recognition in noise with spatially separated speech and noise sources also improved after BAHA implantation, but not significantly. Conclusion: Some patients with congenital unilateral conductive hearing impairment had such good directional hearing and speech-in-noise scores in the unaided situation that no overall significant improvement occurred after BAHA fitting in our setup. Of the 18 patients with a complete data set, 6 did not show any significant improvement at all. However, compliance with BAHA use in this patient group was remarkably high. Observations of consistent use of the device are highly suggestive of patient benefit. Further research is recommended to get more insight into these findings.

Bone-Anchored Hearing Aids in Patients with Acquired and Congenital Unilateral Inner Ear Deafness (Baha CROS): Clinical Evaluation of 56 Cases:

Objectives We performed an evaluation of the audiological and subjective benefits of the bone-anchored hearing aid (Baha) as a device for transcranial routing of sound (Baha CROS) in 56 patients with unilateral inner ear deafness. Methods We performed a prospective clinical follow-up study in a tertiary referral center. Previously reported results of 29 patients were supplemented with a second series of 30 patients with unilateral inner ear deafness; 3 patients dropped out during the evaluation. Audiometric measurements were taken before and after Baha CROS fitting. Subjective benefits were quantified with 4 different patient questionnaires. Results The sound localization results in a well-structured test setting were not differentiable from chance. The 5 patients with congenital hearing loss showed better scores in the unaided sound localization measurements. Overall, most patients reported some subjective improvement in their capacity to localize sounds with the Baha CROS in daily life. The main effect of the Baha CROS was to alleviate the head shadow effect during the speech-in-noise test. Conclusions Poor sound localization in this larger series of patients confirms the findings of previous studies. Improvements in the speech-in-noise scores corroborated the efficacy of the Baha CROS in alleviating the head shadow effect. The 4 different patient questionnaires revealed subjective benefit and satisfaction in various domains.

Genome-wide SNP-based linkage scan identifies a locus on 8q24 for an age-related hearing impairment trait.

Age-related hearing impairment (ARHI), or presbycusis, is a very common multifactorial disorder. Despite the knowledge that genetics play an important role in the etiology of human ARHI as revealed by heritability studies, to date, its precise genetic determinants remain elusive. Here we report the results of a cross-sectional family-based genetic study employing audiometric data. By using principal component analysis, we were able to reduce the dimensionality of this multivariate phenotype while capturing most of the variation and retaining biologically important features of the audiograms. We conducted a genome-wide association as well as a linkage scan with high-density SNP microarrays. Because of the presence of genetic population substructure, association testing was stratified after which evidence was combined by meta-analysis. No association signals reaching genome-wide significance were detected. Linkage analysis identified a linkage peak on 8q24.13-q24.22 for a trait correlated to audiogram shape. The signal reached genome-wide significance, as assessed by simulations. This finding represents the first locus for an ARHI trait.

Bone-anchored hearing aid in patients with moderate mental retardation: impact and benefit assessment.

Objective: To assess the impact and the subjective benefit of Bone-anchored Hearing Aid (BAHA) implementation in patients with hearing impairment combined with moderate mental retardation. Study Design: Case control study using two validated patient-oriented instruments. Setting: Tertiary referral center. Patients: Twenty-two patients with moderate mental retardation and conductive or mixed hearing loss. Intervention: Rehabilitative. Main Outcome Measures: Subjective benefit, listening and learning capabilities. Results: BAHA implementation in patients with moderate mental retardation, by using the Glasgow Childrens Benefit Inventory and the Listening Inventory for Education, showed a subjective benefit, which was comparable with that of the control group and was consistent with the results of earlier studies. Conclusion: The use of BAHA proved beneficial in most patients with hearing impairment and moderate mental retardation. Extending the indications for BAHA application to this special patient group shows to be a very valuable option.

Rehabilitation of patients with conductive hearing loss and moderate mental retardation by means of a bone-anchored hearing aid.

Objective: To evaluate whether the bone-anchored hearing aid (BAHA) can be applied successfully to patients with conductive hearing loss and moderate mental retardation. Study Design: Retrospective clinical evaluation. Setting: Tertiary referral center. Patients: Twenty-two patients with congenital moderate mental retardation and conductive or mixed hearing loss were selected to receive a BAHA at the University Medical Centre Nijmegen, the Netherlands. Four of them were fitted despite a limited air-bone gap. Intervention: Rehabilitative BAHA application. Main Outcome Measures: Implantation results, skin reactions, and audiological data were evaluated during a mean follow-up of 36 months. Results: All the patients were still using the BAHA 7 days a week and for more than 8 hours a day after a follow-up period between 5 and 96 months. Two implants (9%) were lost due to insufficient integration but were reimplanted successfully. With the BAHA, mean free-field thresholds showed a clear mean improvement of 9 dB compared with the previous hearing aid. Considerable improvements in daily activities were seen in at least five patients. Conclusion: Moderate mental retardation should no longer be considered as a contraindication for BAHA application. Although implant loss was low, extra attention may be required from the personal care providers to maintain the percutaneous implant. The BAHA was well-accepted by the patients with moderate mental retardation and was being used for most of the day. Implementation of the BAHA as hearing aid treatment in patients with moderate mental retardation proved to be sufficiently effective and may have strongly positive effects on activities at school or at work.

Familial aggregation of pure tone hearing thresholds in an aging European population.

Objective To investigate the familial correlations and intraclass correlation of age-related hearing impairment (ARHI) in specific frequencies. In addition, heritability estimates were calculated. Study Design Multicenter survey in 8 European centers. Subjects One hundred ninety-eight families consisting of 952 family members, screened by otologic examination and structured interviews. Subjects with general conditions, known to affect hearing thresholds or known otologic cause were excluded from the study. Results We detected familial correlation coefficients of 0.36, 0.37, 0.36, and 0.30 for 0.25, 0.5, 1, and 2 kHz, respectively, and correlation coefficients of 0.20 and 0.18 for 4 and 8 kHz, respectively. Variance components analyses showed that the proportion of the total variance attributable to family differences was between 0.32 and 0.40 for 0.25, 0.5, 1, and 2 kHz and below 0.20 for 4 and 8 kHz. When testing for homogeneity between sib pair types, we observed a larger familial correlation between female than male subjects. Heritability estimates ranged between 0.79 and 0.36 across the frequencies. Discussion Our results indicate that there is a substantial shared familial effect in ARHI. We found that familial aggregation of ARHI is markedly higher in the low frequencies and that there is a trend toward higher familial aggregation in female compared with male subjects.