LOS ANGELES—Impairment of multiple senses is associated with a significantly increased risk of dementia, according to findings presented here at the Alzheimer's Association International Conference.
Researchers said the findings suggest that even mild sensory impairments, when considered together, were associated with cognitive decline, highlighting the importance for more research on the topic.
The investigators examined data from the National Institutes of Health's Health, Aging and Body Composition (Health ABC) study, which includes white and African-American people, ages 70 to 79 at enrollment. A total of 1,818 participants, who had sensory assessments at baseline, were followed for about 11 years, said Willa Brenowitz, PhD, MPH, a post-doctoral fellow at the University of California, San Francisco.
In Health ABC, the researchers assessed vision, smell, hearing, and touch with a battery of tests. Patients in the best performing quartile of each domain were scored as 0 for that domain, the next quartile of impairment were scored as 1, and so on. Then the scores were added up, ranging from 0 to 12, with 12 as the most impaired.
The researchers used the Modified Mini-Mental State Examination and Digit Symbol Substitution test to assess dementia. Incident dementia was based on hospitalization records, dementia medications, and at least a 1.5-point standard deviation decline on the Modified Mini-Mental State Examination.
About 80 percent of those who had the least sensory impairment—those who had scores of 0 to 4 out of 12—were dementia-free at 10 years, researchers found. Each quartile of worse impairment had a lower percentage of dementia-free study participants than the quartile before. In the group with the most sensory impairment—those with scores of 9 to 12—only 60 percent were dementia-free at 10 years, investigators found.
Each 4-point difference in sensory score meant an annual rate of decline of 0.3 points on the 0- to 100-point Modified Mini-Mental State Examination and on the 0- to 91-point DSS, Dr. Brenowitz said.
"Each sensory impairment might have a different etiology that explains its association with dementia, but I think there's this evidence that combining them has a strong association, which hasn't been researched much," Dr. Brenowitz said. "So I think it's an interesting area. The biggest question that remains is whether sensory impairments are potentially modifiable and could impact risk of dementia or whether it's just a pre-clinical indicator of dementia."
She said she and her colleagues, including senior author Kristine Yaffe, MD, are continuing to examine the data. Among other things, they'll be looking at whether there are particular combinations of impairments that are especially important for increased risk of dementia.
David A. Bennett, MD, director of the Rush Alzheimer's Disease Center, said there is a lot of research interest in sensory impairment and dementia; however, much of it is focused on smell, hearing, and vision, but not on touch, which this study incorporates.
"This is a new twist to add them up but the results are not surprising," he said.
"What we don't know from the abstract but would hope to see addressed in the paper is whether these are four relatively unrelated factors that simply have additive effects or whether they are correlated and represent a group of interrelated factors suggesting some common underlying biology."
The findings might be useful broadly but not necessarily for individual care, he said.
"This is a large longitudinal study that has relevance for public health and research," Dr. Bennett said. "The effects are too small to be actionable at the individual level."
Drs. Brenowitz and Bennett reported no disclosures.
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Regan J, Frison E, Collin F, et al. Individualised sensory intervention to improve quality of life in people with dementia and their companions (SENSE-Cog trial): Study protocol for a randomised controlled trial. Trials 2019; 20(1):80.