Kelly Demeester

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.

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.

Audiometric shape and presbycusis

The aim of this study was to describe the prevalence of specific audiogram configurations in a healthy, otologically screened population between 55 and 65 years old. The audiograms of 1147 subjects (549 males and 598 females between 55 and 65 years old) were collected through population registries and classified according to the configuration of hearing loss. Gender and noise/solvent-exposure effects on the prevalence of the different audiogram shapes were determined statistically. In our population ‘Flat’ audiograms were most dominantly represented (37%) followed by ‘High frequency Gently sloping’ audiograms (35%) and ‘High frequency Steeply sloping’ audiograms (27%). ‘Low frequency Ascending’ audiograms, ‘Mid frequency U-shape’ audiograms and ‘Mid frequency Reverse U-shape’ audiograms were very rare (together less than 1%). The ‘Flat’-configuration was significantly more common in females, whereas the ‘High frequency Steeply sloping’-configuration was more common in males. Exposure to noise and/or solvents did not change this finding. In addition, females with a ‘Flat’ audiogram had a significantly larger amount of overall hearing loss compared to males. Furthermore, our data reveal a significant association between the prevalence of ‘High frequency Steeply sloping’ audiograms and the degree of noise/solvent exposure, despite a relatively high proportion of non-exposed subjects showing a ‘High frequency Steeply sloping’ audiogram as well.

Hearing disability measured by the speech, spatial, and qualities of hearing scale in clinically normal-hearing and hearing-impaired middle-aged persons, and disability screening by means of a reduced SSQ (the SSQ5).

Objectives: The goals of the present study were twofold: in the first part, the prevalence and profile of hearing disability in healthy, middle-aged persons were determined by the speech, spatial, and qualities of hearing scale (SSQ). In the second part of this study, the number of SSQ items was reduced to five to make this questionnaire available for routine usage in clinical settings and for screening purposes. Methods: SSQ responses derived from 103 normal-hearing 18- to 25-year-old persons were compared with the SSQ responses of 24 clinically normal-hearing (all thresholds between 125 and 8000 Hz ⩽25 dB HL) and 109 healthy, 55- to 65-year-old persons with age-related hearing impairment to determine the prevalence and profile of hearing disability. The 45 items of the SSQ were reduced to five by cluster analyses and binary logistic regression analyses. The robustness of this five-item version (SSQ5) was determined in three control populations: an adult 25- to 55-year-old population (n = 159), an ENT-patient population (n = 60), and a population of hearing aid candidates (n = 50). The feasibility of the SSQ5 for screening was compared with the feasibility of the simple question “Do you have hearing loss?” by determining, respectively, the sensitivity, specificity, and maximum achievable discriminatory power for predicting hearing status according to speech-in-noise performance. Results: Prevalence numbers showed data of healthy, middle-aged persons with significant disability, despite minimal impairment (25%) versus data of middle-aged persons with significant impairment and nevertheless, minimal disability (61%). The profile of hearing disability seemed similar in all normal-hearing and hearing-impaired subgroups (i.e., most problems with understanding speech especially in noise conditions, and least problems with sound quality). Compared with the single question: “Do you have hearing loss?” the use of the SSQ5 had 37% more maximum discriminatory power for determining hearing status category based on speech-in-noise performance in 55- to 65-year-old persons. In addition, the SSQ5 seemed robust in adult populations of different ages (89.6% correlation between the answers of the SSQ5 and SSQ45), as well as in ENT-patient populations (93.7% correlation) and hearing aid candidate populations (79.2% correlation). Conclusions: The results of this study suggest that disability measures and measures for hearing impairment cannot replace each other, but are complementary. Therefore, it is advised to implement both disability measures and impairment measures in screening and referral policies for hearing loss. To get a first impression of hearing disability, our results suggest that it is useful to ask five disability questions (SSQ5) instead of one general question like “Do you have hearing loss?”

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.