Co‐morbidity of sensory loss (hearing, vision, olfaction) in persons with or at risk for dementia: Implications for brain structure and function

Abstract

AbstractBackgroundHearing, vision, and olfactory loss have each independently been associated with cognitive decline and increased risk for dementia. Research has examined their individual relationships with brain structure and function, but these predictors have not been examined together in older adults who vary along a spectrum of risk for dementia. We examined groups who range from relatively low risk (those with normal cognition and no cognitive complaints (NC)), to those with higher risk, namely individuals with subjective reports of cognitive decline (SCD) but normal cognition and those with mild cognitive impairment (MCI).MethodWe used data from the Comprehensive Assessment of Neurodegeneration and Dementia (COMPASS‐ND) study. Hearing loss was assessed with a pure‐tone screening protocol and a speech‐in‐noise test, vision was assessed with the MNRead for visual acuity and the MARS test for contrast sensitivity, and olfaction was assessed with the Brief Smell Identification Test (BSIT). We examined the frequency of sensory deficits in 60 NC (mean age = 69 years; mean education = 16 years), 55 participants with SCD (age = 70; education = 17), 102 with MCI (age = 72; education = 16), and 47 with Alzheimer’s disease (AD, age = 75; education = 15). Participants were matched on age and education, except for AD participants who were older.ResultsThe frequency of having at least one impairment in at least one sensory domain increased across groups (55% NC, 62% SCD, 75% MCI, 96% AD). A deficit in olfaction was the most common single deficit. Sensory deficits became increasing more co‐morbid across the risk spectrum. Hearing loss and olfaction loss were each associated with lower hippocampal volume and hearing loss was associated with alterations in functional brain connectivity in the default mode network.ConclusionThese analyses indicate that sensory loss is highly frequent and co‐morbid in persons with or at risk for dementia. These findings have implications for cognition, brain function, functional activities, and care delivery for persons with or at risk for dementia.