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Abstract
The purpose of the present study was to examine the relative contribution of genetic and environmental effects on the air-conducted hearing threshold levels at low (0.125–0.5 kHz), mid (1–2 kHz), and high (4–8 kHz) frequencies separately for the better and worse hearing ear in older women. We also examined the distribution of audiogram configurations. Data was analysed using quantitative genetic modelling. As part of the Finnish twin study on aging (FITSA), hearing was measured in 103 monozygotic and 114 dizygotic female twin pairs aged 63–76 years. Approximately every third subject had a flat type, and two-thirds a descending type of audiogram configuration. No significant difference was observed in the distribution of audiogram configurations between zygosity groups. In the better ear, additive genetic effects accounted for 64%–74% of the total variance at different frequencies. For the worse ear, environmental effects were larger. Although overall heritability is rather constant across the frequency spectrum, it is noteworthy that at low and high frequencies frequency-specific genetic and environmental effects together accounted for the majority of the total variance.
| Abbreviations | ||
| A | = | Additive genetic effects |
| ARHI | = | Age-related hearing impairment |
| BMI | = | Body mass index |
| C | = | Common environmental effects |
| CI | = | Confidence interval |
| D | = | Non-additive genetic effects |
| DZ | = | Dizygotic twin |
| DNA | = | Deoxyribonucleic acid |
| E | = | Non-shared environmental effects |
| FITSA | = | Finnish twin study on aging |
| ISO | = | International Organization for Standardization |
| MMSE | = | Mini-mental state examination |
| MZ | = | Monozygotic twin |
| PTA | = | Pure-tone average |
| Abbreviations | ||
| A | = | Additive genetic effects |
| ARHI | = | Age-related hearing impairment |
| BMI | = | Body mass index |
| C | = | Common environmental effects |
| CI | = | Confidence interval |
| D | = | Non-additive genetic effects |
| DZ | = | Dizygotic twin |
| DNA | = | Deoxyribonucleic acid |
| E | = | Non-shared environmental effects |
| FITSA | = | Finnish twin study on aging |
| ISO | = | International Organization for Standardization |
| MMSE | = | Mini-mental state examination |
| MZ | = | Monozygotic twin |
| PTA | = | Pure-tone average |
Sumario
El objetivo de este estudio fue examinar la contribución relativa de la genética y el efecto del medio ambiente en los umbrales auditivos por conducción aérea en frecuencias bajas (0.125–0.5 kHz), medias (1–2 kHz), y altas (4–8 kHz) en forma separada para el mejor y el peor oído en mujeres mayores. También examinamos la distribución de las configuraciones del audiograma. Los datos se analizaron utilizando una modelación genética cuantitativa. Como parte el estudio finlandés de envejecimiento en gemelos, la audición fue medida en 103 y 114 pares de mujeres gemelas monocigotas y dicigotas respectivamente con edades entre 63 y 76 años. Aproximadamente un tercio de los sujetos tenían un audiograma de tipo plano y dos tercios de tipo descendente. No se observaron diferencias significativas en la distribución de la configuración de los audiogramas entre los grupos homo o dicigóticos. En el mejor oído el 64–74% del total de la varianza en diferentes frecuencias, fue atribuido al efecto genético aditivo. Para el peor oído el efecto medio ambiental fue mayor. Aun cuando el factor hereditario es bastante constante a través del espectro de las frecuencias, es de notar que en frecuencias específicas altas y bajas, los efectos genético y ambiental en conjunto fueron responsables por la mayoría del total de la varianza.