July 15, 2019
"Sensory impairments are fairly common in older adults and can serve as a potential marker to help identify patients who may be at high risk for developing dementia," Phillip Hwang, MPH, a doctoral student in epidemiology at the University of Washington, Seattle, noted in an interview with Medscape Medical News.
The research was presented here at the Alzheimer's Association International Conference (AAIC) 2019.
Hwang and colleagues examined the association between hearing and vision impairment and risk for Alzheimer disease (AD) or other dementia in 2150 adults in the Ginkgo Evaluation of Memory (GEM) study. At the time of study enrollment, the participants were aged 75 years or older and were free of dementia.
Sensory impairment was determined at baseline using self-reported responses to questions on vision and hearing. Altogether, 1480 participants (72%) had no sensory impairment, 306 (14.9%) had visual impairment, 161 (7.8%) had hearing impairment, and 104 (5.1%) had both visual and hearing impairment. During 7 years of follow-up, 319 participants were diagnosed with dementia, and 219 were diagnosed with AD dementia.
The number of sensory impairments was associated with risk for all-cause dementia and AD in a graded fashion.
Having either visual or hearing impairment increased the risk of developing dementia by 11% (adjusted hazard ratio [aHR], 1.11; 95% confidence interval [CI], 0.86 – 1.44) and AD dementia by 10% (aHR, 1.10; 95% CI, 0.80 – 1.50), compared with having no sensory impairment.
Having both visual and hearing impairment raised the risk of developing dementia by 86% (aHR, 1.86; 95% CI, 1.25 – 2.79; P < .01) and AD dementia by 112% (aHR, 2.12; 95% CI, 1.34 – 3.36; P < .01).
The results were adjusted for age, sex, race, education, income, body mass index, alcohol consumption, smoking status, physical activity, cardiovascular disease, cerebrovascular disease, diabetes, hypertension, treatment status, and apolipoprotein E status.
In related research presented at the conference, Willa Brenowitz, PhD, MPH, a postdoctoral researcher working with Kristine Yaffe, MD, at the University of California, San Francisco, found that sensory impairment across four domains was strongly associated with an increased risk for dementia and faster cognitive decline.
The study population included 1810 adults aged 70 to 79 from the Health, Aging and Body Composition Study who did not have dementia at the time of enrollment.
On the basis of results of tests of vision, hearing, sense of touch, and smell, the researchers created a summary multisensory function score (0 – 12) for each participant. Incident dementia over a 10-year period was assessed using a combination of hospitalization records, antidementia medication prescriptions, and cognitive decline, as measured by the Modified Mini–Mental State Examination.
Individuals with lower sensory function scores (signaling greater levels of impairment) had significantly increased risk for cognitive decline and dementia. Risk for dementia was 6.8 times higher comparing the worst to the best quartile of multisensory function score.
"Sensory function in multiple domains can be measured during routine healthcare visits using noninvasive or minimally invasive tests," Brenowitz told Medscape Medical News. "Our findings suggest that testing for changes in sensory function may help identify those at high risk for dementia."
Detrimental to the Brain
"This research tells us that depriving the brain of sensory information may have detrimental effects," Maria Carrillo, PhD, chief science officer of the Alzheimer's Association, told Medscape Medical News. "We need more research to confirm these findings and to see if preventing or correcting the sensory impairments can reduce dementia risk," she said.
Gayatri Devi, MD, a neurologist specializing in memory disorders at Lenox Hill Hospital, New York City, was not surprised by the findings.
"Lifestyle factors are important in keeping the brain functioning even when there is Alzheimer's-type brain pathology. Patients with hearing and visual loss may be less likely to participate socially, less likely to engage in physical activities, and less able to care for their ongoing medical conditions. Driving to doctors' appointments may be difficult, for example," Devi told Medscape Medical News.
"These may be factors that contribute to higher risk, but the answers are not currently known. The take-away from the studies is that participating as fully as possible in daily activities, social, physical and mental, keeps the brain healthy and prevents dementia," said Devi.
The study by Hwang and colleagues was supported by the National Center for Complementary and Integrative Health. The study by Brenowitz and colleagues was supported by the Alzheimer's Association and the National Institute on Aging. The authors, Devi, and Carrillo have disclosed no relevant financial relationships.