Genetic and Environmental Contributions to Age-Related Hearing Loss: Results from a Longitudinal Twin Study.

Over 430 million people worldwide experience disabling hearing loss, a condition that becomes more prevalent with age. Although the genetic component to hearing loss has been well established, there has been less data available regarding changes in the genetic contributions to hearing loss over time. We report the pure tone hearing thresholds across 500, 1,000, 2,000, 4,000, and 8,000 Hz from over 1,000 male twins comprising monozygotic (MZ) and dizygotic (DZ) pairs sampled from the United States-based Vietnam Era Twin Study of Aging (VETSA). Twins were tested during three waves, at an average age of 56 at wave 1, an average age of 62 at wave 2, and an average age of 68 at wave 3. Genetically informed structural equation models were used to calculate the genetic contributions. Genetic factors accounted for between 49.4% and 67.7% of the variance in hearing acuity for all frequencies at all three time points. There was no substantial change in the ratio of genetic versus environmental contributions across the three time points, or across individual acoustic frequencies. The stability of hearing acuity over time was moderate to highly attributable to genetic factors. Change in hearing acuity was better explained by unique person-specific environmental factors. These results, from the largest-scale twin study of hearing acuity to date, replicate previous findings that hearing acuity in late life is significantly determined by genetic factors. The unique contribution of the present analysis is that the proportion of hearing acuity attributed to genetics remains relatively consistent across 12 years.