Genetic and environmental influences on hearing in older women.

BACKGROUND This study examined the relative contribution of genetic and environmental effects on the air-conducted hearing threshold level (0.5-4 kHz) and speech recognition threshold level of the better ear as well as self-reported hearing in older women. METHODS Hearing was measured as a part of the Finnish Twin Study on Aging in 103 monozygotic (MZ) and 114 dizygotic (DZ) female twin pairs aged 63-76 years. Audiometric measured hearing was tested using standardized methods in soundproof conditions. Self-reported hearing was assessed by a structured question. Quantitative genetic modeling was used for data analyses. RESULTS No significant differences in age, exposure to noise, hearing-aid use, auditory diseases or accidents, or number of self-reported chronic conditions or prescription medicines were observed between the MZ and DZ twins. A genetic component in common accounted for 75% (95% confidence interval [CI], 67%-81%) of the variance in the better ear's hearing threshold level and 54% (95% CI, 43%-64%) in the better ear's speech recognition threshold level, according to a bivariate genetic analysis. In addition, 10% (95% CI, 4%-15%) of the variance in the better ear's speech recognition threshold level was explained by its specific genetic component. CONCLUSION Individual differences in audiometrically measured air-conducted hearing threshold level (0.5-4 kHz) and speech recognition threshold level in the better ear were largely accounted for by genetic differences between individuals. In contrast, self-reported hearing appears to be accounted for solely by environmental factors.