Multisensory Impairment Is Associated With Risk of Dementia

LOS ANGELES—Among older adults, the presence of a greater number of sensory impairments is associated with an increased risk of dementia, according to research presented at the 70th Annual Meeting of the American Academy of Neurology.

Sensory impairments are common among older adults and are associated with dementia, but no study has examined multisensory impairment and risk of dementia by incorporating measures of hearing, vision, smell, and touch, said Willa D. Brenowitz, PhD, MPH, a researcher in the Department of Epidemiology and Biostatistics at the University of California, San Francisco, and colleagues.

To evaluate whether the presence of multiple sensory impairments is associated with a greater risk of dementia, compared with a single or no sensory impairment, Dr. Brenowitz and colleagues studied 1,843 participants from the Health, Aging, and Body Composition Study. Participants were ages 70 to 79 and did not have dementia at baseline.

Investigators used sensory assessments that were conducted during the study years 3–5 to determine whether participants had visual impairment (ie, visual acuity ≤ 20/40 or log contrast sensitivity < 1.55), moderate to severe hearing loss (> 40 decibels hearing level based on pure tone average at 500 Hz, 1,000 Hz, 2,000 Hz, and 4,000 Hz), poor smell (lowest tertile of 12-item Cross Cultural Smell Identification Test), or impaired touch (peripheral nerve insensitivity based on a 10-g monofilament test or vibration detection threshold).

Investigators followed participants for up to 10 years. Incident dementia was based on hospitalization records, dementia medications, or a decline in Modified Mini-Mental State Exam of 1.5 standard deviations or greater. The researchers evaluated the association between number of sensory impairments and risk of dementia using Cox proportional hazard models adjusted for demographics and health conditions.

Sensory impairments were common, the researchers said. In all, 28% had visual impairments, 35% had hearing loss, 22% had poor smell, 12% had peripheral nerve insensitivity, and 25% had multiple impairments. An increasing number of impairments was associated with risk of dementia in a graded fashion. Compared with no sensory impairment, having one sensory impairment was associated with a 50% greater risk of dementia, two impairments was associated with a twofold greater risk of dementia, and three or four impairments was associated with a 2.8-fold greater risk of dementia.

“It is possible that sensory impairment, especially multiple [impairments], could limit an older adult’s engagement in protective lifestyle factors such as cognitive, physical, and social activity, thereby increasing dementia risk,” Dr. Brenowitz and colleagues said.

Clinical assessment of sensory function may help identify patients at high risk of dementia. Further studies are needed to determine whether multisensory impairment is a risk factor for dementia or an indicator of neurodegeneration, the researchers said.

—Jake Remaly