Association of hearing, vision, and dual sensory impairment and risk of Alzheimer's disease: a nested case-control study.

Background: Hearing impairment is a known risk factor for Alzheimer's disease (AD), although less is known about vision impairment or dual sensory impairment (DSI) as risk factors for AD. We studied the association between diagnosed hearing impairment, visual impairment, or DSI, and the risk of AD.

Method: The Medication use and Alzheimer's disease study (MEDALZ) is a register-based nested case-control study including 70,718 community-dwelling persons diagnosed with incident AD in 2005-2011 in Finland and their 282,845 matched controls. Sensory impairment diagnoses (limited to those that cause irreversible sensory loss designated by medical specialists) at least five years prior to AD diagnosis (or matching date) were obtained from national healthcare registers, including specialized outpatient visits. Associations were studied with cofounder-adjusted conditional logistic regression.

Results: Hearing impairment was associated with an increased risk of AD compared to people without a diagnosed sensory impairment (adjusted odds ratio (aOR) 1.15, 95% confidence interval (CI) 1.11-1.19), while no association was found in people with visual (aOR 1.02, 95% CI 0.99-1.05) or dual sensory impairment (aOR 1.05 (95% CI 0.95-1.15).

Conclusions: Hearing impairment can be a modifiable risk factor for AD, and thus its treatment in the aging population is important. Although we did not observe an association between visual impairment and AD, all sensory impairments decrease functioning and quality of life among older adults. Therefore, they should be treated, also among persons with cognitive decline or cognitive disorder.

Clinical trial number: Not Applicable.