5295.0: Wednesday, November 15, 2000 - 5:30 PM

Abstract #16792

Modeling genetic influences on age-related hearing impairment using the Danish National Twin Registry

Kaare Christensen, MD, PhD, DrMed, Epidemiology Department, Institute of Public Health, University of Southern Denmark--Odense University, Sdr. Boulevard 23A, DK-5000 Odense C, Denmark, +45 6550 3049, KChristensen@health.sdu.dk and Howard J. Hoffman, MA, Epidemiology, Statistics and Data System Branch, National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, Executive Plaza South Bldg., Suite 432, 6120 Executive Boulevard, MSC 7180, Bethesda, MD 20892-7180.

Our objective is to estimate the relative importance of genetic and environmental factors to variation in self-reported reduced hearing among the elderly. We conducted a survey among all Danish 75+ year old twins identified in the population-based Danish Twin Registry. Among 3,099 individuals in the study population, interviews were conducted with 77%. In 1997 follow-up contact was made and an additional 779 twins aged 73-76 were included in the study. Reduced hearing was assessed by the same question in both interview waves. Heritability (proportion of population variance attributable to genetic variation) was estimated using structural-equation analyses. The prevalence of self-reported reduced hearing corresponded to previous studies and showed the expected age- and sex-dependence. Concordance rates, odds ratios and correlations were consistently higher for monozygotic twin pairs compared with dizygotic twin pairs in all age and sex categories, indicating heritable effects. Structural-equation analyses revealed substantial heritability for self-reported reduced hearing: 45-52% (depending on the model). The remaining variation could be attributed to individuals' non-familial environments. A recent male twin study reported that genetic influence on variation in hearing ability in the high frequency range decreased with age, however, few persons above the age of 70 were included. We found that genetic factors explain about half the variation in self-reported reduced hearing in both males and females aged 73 or older. Because self-reports of reduced hearing involve misclassification, this estimate is probably conservative. Hence, our study suggests that genetic factors play a major role in reduced hearing among the elderly and oldest-old.

Learning Objectives: After this talk, participants will be able to: 1) describe the high prevalence of hearing impairment among the elderly (75+ years old); 2) recognize that a health questionnaire survey of a population-based twin sample can be used to estimate "heritability" (the proportion of variance attributable to genetic variation); 3) recognize that even age-related hearing loss (presbycusis) has a large genetic component (heritability of about 50%)

Keywords: Genetics, Deaf

Presenting author's disclosure statement:
Organization/institution whose products or services will be discussed: None
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.

The 128th Annual Meeting of APHA