Prevalence, Incidence Proportion, and Heritability for Tinnitus: A Longitudinal Twin Study.

OBJECTIVES: The purpose of this longitudinal twin study was to explore the effect of tinnitus on hearing thresholds and threshold shifts over two decades and to investigate the genetic contribution to tinnitus in a male twin cohort (n = 1114 at baseline and 583 at follow-up). The hypothesis was that participants with faster hearing deterioration had a higher risk for developing tinnitus and there is an underlying role of genetic influences on tinnitus. DESIGN: Male mono- and dizygotic twin pairs, born between 1914 and 1958 were included. Mixed models were used for comparison of hearing threshold shifts, adjusted for age. A co-twin comparison was made within pairs discordant for tinnitus. The relative influence of genetic and environmental factors was estimated by genetic modeling. RESULTS: The overall prevalence of tinnitus was 13.5% at baseline ((Equation is included in full-text article.)age 50) and 34.4% at follow-up ((Equation is included in full-text article.)age 67). The overall incidence proportion was 27.8%. Participants who reported tinnitus at baseline or at both time points were older. At baseline, the hearing thresholds differed between tinnitus cases and controls at all frequencies. New tinnitus cases at follow-up had the greatest hearing threshold shift at the high-frequency area compared with the control group. Within pairs, the tinnitus twin had poorer hearing than his unaffected co-twin, more so for dizygotic than monozygotic twin pairs. The relative proportion of additive genetic factors was approximately 0.40 at both time points, and the influence of individual-specific environment was 0.56 to 0.61. The influence of genetic factors on tinnitus was largely independent of genetic factors for hearing thresholds. CONCLUSIONS: Our hypotheses were confirmed: The fastest hearing deterioration occurred for new tinnitus cases. A moderate genetic influence for tinnitus was confirmed.

Influence of well-known risk factors for hearing loss in a longitudinal twin study.

OBJECTIVE: The aim was to investigate the influence of environmental exposures on hearing loss in a twin cohort. STUDY SAMPLE: Male twins born 1914-1958, representing an unscreened population, were tested for hearing loss at two occasions, 18 years apart. DESIGN: Clinical audiometry and a questionnaire were performed at both time points in this longitudinal study. Noise and solvent exposure were assessed using occupational work codes and a job exposure matrix. Hearing impairment was investigated using two different pure tone averages: PTA4 (0.5, 1, 2, and 4 kHz) and HPTA4 (3, 4, 6, and 8 kHz). RESULTS: Age affected all outcome measures. Noise exposure between time point one and two affected the threshold shifts of PTA4 and HPTA4 more in participants with a pre-existing hearing loss at time point one. Lifetime occupational noise exposure was a risk factor especially for the low-frequency hearing threshold PTA4. Firearm use was a statistically significant risk factor for all outcome measures. CONCLUSIONS: Pre-existing hearing loss can increase the risk of hearing impairment due to occupational noise exposure. An increased risk for NIHL was also seen in the group with exposures below 85 dB(A), a result that indicates awareness of NIHL should be raised even for those working in environments where sound levels are below 85 dB(A).

Reliability in Hearing Threshold Prediction in Normal-Hearing and Hearing-Impaired Participants Using Mixed Multiple ASSR.

BACKGROUND AND PURPOSE: The rapidly evolving field of hearing aid fitting in infants requires rapid, objective, and highly reliable methods for diagnosing hearing impairment. The aim was to determine test-retest reliability in hearing thresholds predicted by multiple auditory steady-state response (ASSRthr) among normal-hearing (NH) and hearing-impaired (HI) adults, and to study differences between ASSRthr and pure-tone threshold (PTT) as a function of frequency in each participant. ASSR amplitude versus stimulus level was analyzed to study ASSR growth rate in NH and HI participants, especially at ASSRthr. RESEARCH DESIGN AND STUDY SAMPLE: Mixed multiple ASSR (100% AM, 20% FM), using long-time averaging at a wide range of stimulus levels, and PTT were recorded in 10 NH and 14 HI adults. ASSRthr was obtained in 10 dB steps simultaneously in both ears using a test-retest protocol (center frequencies = 500, 1000, 2000, and 4000 Hz; modulation frequencies = 80-96 Hz). The growth rate at ASSRthr was calculated as the slope (nV/dB) of the ASSR amplitudes obtained at, and 10 dB above, ASSRthr. PTT was obtained in both ears in 1 dB steps using a fixed-frequency Békésy technique. All of the NH participants showed PTTs better than 20 dB HL (125-8000 Hz), and mean pure-tone average (PTA; 500-4000 Hz) was 1.8 dB HL. The HI participants exhibited quite symmetrical sensorineural hearing losses, as revealed by a mean interaural PTA difference of 6.5 dB. Their mean PTA in the better ear was 38.7 dB HL. RESULTS: High ASSRthr reproducibility (independent of PTT) was found in both NH and HI participants (test-retest interquartile range = 10 dB). The prediction error was numerically higher in NH participants (f ≥1000 Hz), although only a significant difference existed at 1000 Hz. The median difference between ASSRthr (dB HL) and PTT (dB HL) was approximately 10 dB in the HI group at frequencies of 1000 Hz or greater, and 20 dB at 500 Hz. In general, the prediction error decreased (p < 0.001) with increasing hearing threshold, although large intersubject variability existed. Regression analysis (PTT versus ASSRthr) in HI participants revealed correlation coefficients between 0.72-0.88 (500-4000 Hz) and slopes at approximately 1.0. Large variability in ASSRthr-PTT versus frequency was demonstrated across HI participants (interquartile range approximately 20 dB). The maximum across-frequency difference (ASSRthr-PTT) in an individual participant was 50 dB. HI participants showed overall significantly higher amplitudes and slopes at ASSRthr than did NH participants (p < 0.02). The amplitude-intensity function revealed monotonically increasing ASSRs in NH participants (slope 2 nV/dB), whereas HI participants exhibited heterogeneous and mostly nonmonotonically increasing ASSRs. CONCLUSIONS: Long-time averaging of ASSR revealed high ASSRthr reproducibility and systematic decrease in prediction error with increasing hearing threshold, albeit large intersubject variability in prediction error existed. A plausible explanation for the systematic difference in ASSRthr between NH and HI adults might be significantly higher ASSR amplitudes and higher overall growth rates at ASSRthr among HI participants. Across-frequency comparison of PTT and ASSRthr in an individual HI participant demonstrated large variation; thus, ASSR may not be optimal for, e.g., reliable threshold prediction in infants and subsequent fine-tuning of hearing aids.

The role of genetic factors for hearing deterioration across 20 years: a twin study.

BACKGROUND: Hearing deterioration at advanced ages is associated with environmental exposures (eg, to noise and solvents) and genetic influences may also be important. Little is known about the role of genetic influences on hearing when evaluated longitudinally. We sought to investigate longitudinal hearing loss in a cohort of adult male twins to evaluate the importance of genetic and environmental factors for hearing deterioration over time. METHODS: Hearing using conventional clinical audiometry was assessed in 583 male twins (128 monozygotic twin pairs and 111 dizygotic twin pairs) aged 34-79 at baseline and again two decades later. The hearing thresholds at two time points were compared at each frequency and in two different frequency regions. Genetic analyses were based on structural equation models. Bivariate Cholesky decomposition was used for longitudinal analysis. RESULTS: The prevalence of hearing loss increased over time in better and worse ear. The hearing threshold shift was more pronounced in the high-frequency region, especially at 8000 Hz. Genetic influences were moderate (heritability: 53%-65%) for pure-tone averages at both lower and higher frequencies, and were of equal magnitude at baseline and follow-up. In contrast, environmental influences were of substantial importance (55%-88%) for rate of change of the hearing threshold over the 18-year period. CONCLUSIONS: Genetic factors are of considerable importance for level of hearing acuity, but environmental factors are more important for rate of change over an 18-year period.

Prevalencia de defectos del desarrollo del esmalte en los incisivos permanentes de escoalres: un estudio fotográfico en el Sur de Brasil

El objetivo de este estudio fue evaluar la prevalencia y distribución de diferentes tipos de problemas de desarrollo del esmalte (DDE) en los incisivos de los escolares de una población de la pequeña ciudad del sur de Brasil. Examinamos a todos los niños y olescentes que asistieron, del 5 al 8 º grado de educación en las escuelas públicas en la ciudad de Camboriu - SC, cuyas escuelas y cuyos padres aceptaron de forma individual y dieron su consentimiento para su participación. Fueron incluidos en el estudioaquellos que presentaban incisivos con al menos tres cuartas partes de la corona en erupción y en condiciones de ser examinados (sin aparatología ortodontica, fractura, lesión cariosa o restauración extensa, n = 223). Dos evaluadores, previamente capacitados utilizaron los criterios clínicos del "FDI World Dental Federation" parael diagnóstico de DDE, a través de proyección de imágenes de fotografías de los incisivos. Análisis descriptivo y test de Chi-cuadrado. 1728 dientes se clasificaron de acuerdo a la presencia de DDE. La prevalencia de DDE fue del 34,1 por ciento para los escolares, siendo que 10,3 por ciento de los dientes examinados presentaron algún tipode DDE. La prevalencia de las diferentes alteraciones en los incisivos examinados fueron: opacidad difusa (6,6 por ciento), opacidad demarcada (3,4 por ciento)e hipoplasia (0,4 por ciento) y las clasificaciones mas frecuentes fueron la opacidad difusa lineal (3,7 por ciento), seguido por opacidad blanca demarcada (3 por ciento) yopacidad difusa irregular (2,8 por ciento). Hubo una asociación estadísticamente significativa (p <0,001) entre la presencia de DDE y la arcada dentaria,siendo los incisivos superiores más afectados. Los incisivos centrales fueron estadísticamente más afectados (p <0,001) que los laterales. Losincisivos inferiores mostraron una prevalencia similar de DDE entre sí. No hubo diferencias estadísticamente significativas en la prevalencia de DDE en función del género y el lado del diente. Se concluye que la presencia de DDE en losincisivos permanentes de los escolares en el sur de Brasil fue alta, es importante que el cirujano dentista sea capaz de diagnosticar e identificar los posibles factores etiológicos. (AU) FONTE olution,