The Laterality of Early Age-Related Hearing Loss and Brain β-Amyloid.

OBJECTIVE

Worse hearing was linked to higher brain β-amyloid, a pathologic hallmark of Alzheimer's disease, in a recent study. We analyze the associations between β-amyloid and early age-related hearing loss in the right versus left ear to explore the laterality of this relationship.

STUDY DESIGN

Cross-sectional analysis of a prospective cohort study.

SETTING

Tertiary referral center.

PARTICIPANTS

Ninety-eight late middle-age adults.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

The primary outcome was whole brain and regional β-amyloid standardized uptake value ratio (SUVR) on positron emission tomography. The exposure was hearing in the right and left ear, measured by pure tone average (PTA) and word recognition score (WRS). Linear regression analyzed the association between β-amyloid and hearing in each ear, adjusting for potential confounders, including age, gender, education, cardiovascular disease, and hearing aid use.

RESULTS

Mean age ± standard deviation was 64.3 ± 3.5 years. Mean PTA was 20.4 ± 8.8 dB. Multivariable regression adjusting for covariates demonstrated that a 10 dB worsening in PTA in the left ear was associated with significantly higher β-amyloid (SUVR) in the bilateral cingulate gyri (right coefficient: 0.029 [95% confidence interval: 0.003-0.054]; left: 0.029 [0.003-0.055]), bilateral frontal lobes (right: 0.024 [0.002-0.047]; left: 0.028 [0.006-0.049]), and the right temporal lobe (0.019 [0.002-0.037]). Consistent results were observed when WRS served as the exposure. No associations were observed between β-amyloid and PTA or WRS in the right ear.

CONCLUSIONS

Worse hearing in the left ear, but not the right ear, was associated with higher β-amyloid. This might relate to asymmetric central auditory processing.