title: The role of genetic factors for hearing deterioration across 20 years: a twin study.
abstract: 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.
authors: Department of Clinical Science, Intervention and Technology, Section of Audiology, Karolinska Institutet, Huddinge, Sweden.
authors: Renata
authors: R
authors: Bogo
authors: Public Health Agency of Sweden, Stockholm, Sweden.
authors: Ahmed
authors: A
authors: Farah
authors: Department of Clinical Science, Intervention and Technology, Section of Audiology, Karolinska Institutet, Huddinge, Sweden.
authors: Ann-Christin
authors: AC
authors: Johnson
authors: Department of Audiology and Neurotology, Karolinska University Hospital, Huddinge, Sweden.
authors: Kjell K
authors: KK
authors: Karlsson
authors: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors: Nancy L
authors: NL
authors: Pedersen
authors: Department of Occupational and Environmental Medicine, Uppsala University, Uppsala, Sweden.
authors: Magnus
authors: M
authors: Svartengren
authors: Department of Clinical Science, Intervention and Technology, Section of Audiology, Karolinska Institutet, Huddinge, Sweden. Department of Audiology and Neurotology, Karolinska University Hospital, Huddinge, Sweden. asa.skjonsberg@ki.se.
authors: Åsa
authors: Å
authors: Skjönsberg
mesh_terms: D000368:Aged; D000375:Aging / Q000235:genetics*; D001301:Audiometry, Pure-Tone; D005260:Female; D034381:Hearing Loss / Q000453:epidemiology / Q000235:genetics*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic
keywords: Aging; Genetic; Hearing loss; Pure-tone average; Threshold shift; Twins.