Good sense of smell may indicate lower risk of dementia in older adults: study

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“Stop and smell the roses” may actually be important when it comes to detecting your risk for dementia and getting early treatment for the condition, according to a new study.

A study out of the University of California San Francisco found that older Americans who can identify odors like roses, lemons, onions, paint-thinner, and turpentine may have half the risk of developing dementia compared to those with significant sensory loss, according to researchers performing the study.

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“The olfactory bulb, which is critical for smell, is affected fairly early on in the course of the disease,” said first author Willa Brenowitz, Ph.D., of the UCSF Department of Psychiatry and Behavioral Sciences and the Weill Institute for Neurosciences, in a statement. “It’s thought that smell may be a preclinical indicator of dementia, while hearing and vision may have more of a role in promoting dementia.”

Researchers at UCSF investigated the effects of multiple declining senses such as seeing, hearing, touching, and smelling on impaired cognition.

According to the study published this month in Alzheimer's and Dementia: The Journal of the Alzheimer's Association, the investigators followed 1,794 adults aged 70 to 79 for a period of 10 years to see if there was a correlation between their sensory function and the presence of dementia. At the time of enrollment, none of the participants were diagnosed with dementia, but throughout the period of the study, 328 (18 percent) developed the condition.

The researchers told Fox News that the participants’ sensory functions involving smell, vision, hearing, and touch were measured and their sensory level scores were placed into three categories: good, middle, and poor. That score was then evaluated with the presence of any associated dementia.

Those participants whose sensory level function ranked in the poor range had double the risk of dementia compared to those in the good range, the study authors said.

"Individuals with worse function in multiple senses may be at higher risk for dementia," Brenowitz said. (iStock)

"Individuals with worse function in multiple senses may be at higher risk for dementia," Brenowitz told Fox News. "We don’t know exactly why [a] multisensory function is associated with dementia but there could be several reasons, such as being a marker for early stages dementia or some senses could affect dementia."

Of the senses studied, the authors said the loss of smell is likely more of a marker for dementia compared to the other senses. One reason, Brenowitz hypothesized, is "because the brain region important for smell is affected in Alzheimer’s disease."

The cause of impaired senses, the researchers explained, could be due to disease processes like a stroke or underlying neurological degeneration.

“Alternatively, sensory impairments, particularly hearing and vision, may accelerate cognitive decline, either directly impacting cognition or indirectly by increasing social isolation, poor mobility, and adverse mental health," according to the study's news release.

“Even mild or moderate sensory impairments across multiple domains were associated with an increased risk of dementia, indicating that people with poor multisensory function are a high-risk population that could be targeted prior to dementia onset for intervention," said Senior Author Dr. Kristine Yaffe, of the UCSF departments of Psychiatry and Behavioral Sciences, Epidemiology and Biostatistics, and Neurology.

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"In the context of dementia, loss of smell is more lasting and likely progressive. Hearing and vision though offer more promise as they can be corrected and may affect social engagement and physical mobility which are also linked to a reduced risk of dementia," Brenowitz added.

Both authors hope this study will foster further research in the area of early detection and intervention for signs of dementia.