Two studies reported at the Alzheimer’s Association International Conference (AAIC) 2019 in Los Angeles found that experiencing multiple sensory impairments, such as vision and hearing problems, are associated with an increased risk of developing dementia in older adults, the AAIC announced on its website.
Emerging science shows that sensory dysfunction can increase the risk of dementia, and the new research presented at AAIC 2019 further demonstrates the impact of multiple co-occurring sensory impairments.

Research from the University of Washington School of Public Health showed that impairment of either vision or hearing increases the risk of developing dementia, and that impairment in both senses further increases those odds. Meanwhile, researchers at the University of California, San Francisco studied the combined effects of loss of smell, touch, vision, and hearing; they found that even mild impairments in multiple senses were associated with an increased risk of dementia and cognitive decline.

“We’re beginning to learn through these new research findings that sensory impairments, even those that are very mild, may also be associated with increased risk of dementia, especially when there are several of them at the same time,” said Maria C. Carrillo, PhD, Alzheimer’s Association chief science officer. “We need more research to confirm these initial findings and to see if correcting the sensory impairments can reduce dementia risk.”

Combined Visual and Hearing Impairment Increases Risk of Dementia in Older Adults

While recent studies have shown that loss of sensory function increases risk of developing dementia, very little is known about the impact of co-occurring sensory impairments. In order to understand the effect of dual sensory impairment on the development of dementia, Phillip Hwang, MPH, a doctoral epidemiology student at the University of Washington, and colleagues examined the association between hearing and vision impairment and risk of Alzheimer’s or other dementia in 2,051 people from the Ginkgo Evaluation of Memory Study aged 75 or older who did not have dementia at the time of study enrollment.

Baseline sensory impairment was established through self-reported responses to a set of questions on hearing and vision. Over seven years of follow-up, incident dementia was assessed based on clinical diagnosis using DSM-IV criteria, and Alzheimer’s disease was determined using criteria developed by the National Institute of Neurological and Communicative Disorders and Stroke—Alzheimer’s Disease and Related Disorders Association (NINCDS-ADRDA; the ADRDA is now known as the Alzheimer’s Association).

The researchers found that the number of sensory impairments was associated with risk of all-cause dementia and Alzheimer’s disease (both p≤0.01) in a graded fashion. Having either visual or hearing impairment increased the risk of developing dementia by 11% and Alzheimer’s by 10%. Having both visual and hearing impairment raised the risk of developing dementia by 86% and Alzheimer’s by 112%.

“These findings suggest that co-occurring hearing and vision problems in late life are strongly associated with increased risk of all-cause dementia and Alzheimer’s dementia,” said Hwang. “Impairment of more than one sense seems to increase risk of dementia synergistically.”

“Assessment of visual and hearing function may help identify older adults at high risk of developing dementia,” Hwang added.

Even Mild Multisensory Impairment is Associated With Dementia and Cognitive Decline

Willa D. Brenowitz, PhD, MPH, a postdoctoral researcher at the University of California, San Francisco, working with Kristine Yaffe, MD, and colleagues conducted a study of impairments in vision, hearing, smell, and touch to investigate the effect of multisensory impairment on dementia risk.

The researchers studied a group of 1,810 older Americans aged 70-79 from the Health, Aging and Body Composition (ABC) Study who did not have dementia at the time of enrollment. They assessed sight, hearing, touch, and smell to create a summary multisensory function score for each participant. Incident dementia over 10 years was assessed using a combination of hospitalization records, anti-dementia medication prescriptions, and cognitive decline as measured by the Modified Mini-Mental State Exam (3MS).

The researchers found that participants with lower sensory function scores—thus, greater levels of impairment—had significantly increased risk of both dementia and cognitive decline (both p“Depression, Hearing Loss, and Treatment with Hearing Aids” mentions several of these studies.

Original Papers: Hwang P, et al. Dual sensory impairment in older adults and risk of dementia and Alzheimer’s disease. Paper presented at:  Alzheimer’s Association International Conference (AAIC) 2019; July 14-18, 2019; Los Angeles, CA. https://www.alz.org/aaic.

Brenowitz WD, et al. Multisensory impairment and dementia: worsening function in multiple senses is associated with dementia and cognitive decline. Paper presented at: Alzheimer’s Association International Conference (AAIC) 2019; July 14-18, 2019; Los Angeles, CA. https://www.alz.org/aaic.

Source: AAIC