AGE-RELATED HEARING LOSS, LATE-LIFE DEPRESSION, AND RISK FOR INCIDENT DEMENTIA IN OLDER ADULTS

Introduction Age-related hearing loss, late-life depression, and dementia are three prevalent and disabling conditions found in older adults, but the inter-relationships between these disorders remain poorly understood. We aimed to determine whether the presence of hearing loss increases risk for incident depression and dementia, and examine whether depression partially mediates the hearing loss-dementia relationship. Methods Data from the National Alzheimer's Coordinating Center (NACC) Uniform Dataset were used to evaluate Cox proportional hazard models to determine the effect of hearing loss on incident depression and dementia. A total of 8,529 participants aged 60?years or older who were free of dementia or cognitive impairment at their first NACC visit were available for analysis. Hearing categories included no hearing loss, untreated hearing loss, and treated hearing loss. The main outcome measures were incident depression (15-item Geriatric Depression Scale ≥5) and conversion to dementia (as defined by the Alzheimer's Disease Centers Clinical Task Force). Two Cox proportional hazard models were used: Model A included only baseline variables (hearing loss, depression, and demographics) and Model B included time-varying depression in order to evaluate for the direct effect of incident depression on dementia over time. Results Subjects with treated hearing loss had increased risk for incident depression (OR = 1.24, 95% CI 1.02-1.51) and conversion to dementia (HR = 1.27, 95% CI 1.02-1.60). The presence of baseline depression was a strong independent predictor of conversion to dementia (HR = 2.44, 95% CI 1.86-3.21). Development of depression partially mediated the pathway from hearing loss to dementia, accounting for 8% of the direct hearing-dementia relationship (beta = 0.24 [SE 0.12] in Model A to beta = 0.22 [SE 0.12] in Model B). Conclusions Both hearing loss and depression are independent risk factors for eventual conversion to dementia. The development of depression in a hearing-impaired older adult may be an intermediate step in this pathway. Understanding the brain and behavioral mechanisms linking these conditions may facilitate identification and dissemination of interventions (such as treatment for hearing loss and depression) capable of protecting brain health during aging. This research was funded by: None