Association of genetic risk for Alzheimer disease and hearing impairment

To test the hypothesis that incipient AD may adversely affect hearing and that hearing loss may adversely affect cognition we evaluated whether (1) genetic variants that increase AD risk also increase problem hearing and (2) genetic variants that increase hearing impairment risk do not influence cognition. UK Biobank participants without dementia aged 56+ with Caucasian genetic ancestry completed a Digit Triplets Test of speech-in-noise hearing (n = 80,074), self-reported problem hearing and hearing with background noise (n = 244,915) and completed brief cognitive assessments. A genetic risk score for AD (AD-GRS) was calculated as a weighted sum of 23 previously identified AD-related polymorphisms. A genetic risk score for hearing (hearing-GRS) was calculated using 3 previously identified polymorphisms related to hearing impairment. Using age-, sex-, and genetic ancestry-adjusted logistic and linear regression models, we evaluated (1) whether the AD-GRS predicted poor hearing and (2) whether the hearing-GRS predicted worse cognition. Poor speech-in-noise hearing (>-5.5 dB speech reception threshold; prevalence = 14%) was associated with lower cognitive scores (ß = -1.28; 95% CI: -1.54, -1.03). Higher AD-GRS was significantly associated with poor speech-in-noise hearing (OR = 1.06; 95% CI: 1.01, 1.11) and self-reported problems hearing with background noise (OR = 1.03; 95% CI: 1.00, 1.05). Hearing-GRS was not significantly associated with cognitive scores (ß = -0.05; 95% CI: -0.17, 0.07). Genetic risk for AD also influences speech-in-noise hearing. We failed to find evidence that genetic risk for hearing impairment affects cognition. AD disease processes or a shared etiology may cause speech-in-noise difficulty prior to dementia onset.

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