(Reuters Health) – Older adults with a poor sense of smell may die sooner than their counterparts who have keen olfactory abilities, a U.S. study suggests.
Researchers asked 2,289 adults, ages 71 to 82, to identify 12 common smells, awarding scores from zero to as high as 12 based on how many scents they got right. When they joined the study, none of the participants were frail: they could walk a quarter mile, climb 10 steps, and independently complete daily activities.
During 13 years of follow-up, 1,211 participants died.
Overall, participants with a weak nose were 46 percent more likely to die by year 10 and 30 percent more apt to pass away by year 13 than people with a good sense of smell, the study found.
“The association was largely limited to participants who reported good-to-excellent health at enrollment, suggesting that poor sense of smell is an early and sensitive sign for deteriorating health before it is clinically recognizable,” said senior study author Dr. Honglei Chen of Michigan State University in East Lansing.
“Poor sense of smell is likely an important health marker in older adults beyond what we have already known about (i.e., connections with dementia, Parkinson’s disease, poor nutrition, and safety hazards),” Chen said by email.
People who started out the study in excellent or good health were 62 percent more likely to die by year 10 when they had a poor sense of smell than when they had a keen nose, researchers report in the Annals of Internal Medicine.
But smell didn’t appear to make a meaningful difference in mortality rates for people who were in fair to poor health at the start of the study.
With a poor sense of smell, people were more likely to die of neurodegenerative and cardiovascular diseases, but not of cancer or respiratory conditions.
Poor sense of smell may be an early warning for poor health in older age that goes beyond neurodegenerative diseases that are often signal the beginning of physical or mental decline, the results also suggest.
Dementia or Parkinson disease explained only 22 percent of the higher death risk tied to a poor sense of smell, while weight loss explained just six percent of this connection, researchers estimated. That leaves more than 70 percent of the higher mortality rates tied to a weak nose unexplained.
The connection between a poor sense of smell and mortality risk didn’t appear to differ by sex or race or based on individuals’ demographic characteristics, lifestyle, and or chronic health conditions.
One limitation of the study is that the older adult participants were relatively functional, making it possible results might differ for younger people or for frail elderly individuals, the study team writes.
Researchers also only tested smell at one point in time, and they didn’t look at whether changes in olfactory abilities over time might influence mortality. Researchers also lacked data on certain medical causes of a weak nose such as nasal surgery or chronic rhinosinusitis that are not related to aging.
“The take-home message is that a loss in the sense of smell may serve as a bellwether for declining health,” said Vidyulata Kamath of the Johns Hopkins University School of Medicine in Baltimore, co-author of an accompanying editorial.
“As we age, we may be unaware of declining olfactory abilities,” Kamath said by email. “Given this discrepancy, routine olfactory assessment in older adults may have clinical utility in screening persons at risk for illness, injury or disease for whom additional clinical work-up and/or intervention may be warranted.”
Lisa Rapaport APRIL 29, 2019
SOURCE: bit.ly/2vrDJkP Annals of Internal Medicine, online April 29, 2019.
www.reuters.com
Humans Smell With Their Tongues, Scientists Discover
The receptors that dot our noses and help us to smell also populate our tongues, according to a new study. Researchers at the Monell Chemical Senses Center have discovered working olfactory (smell) receptors in the taste-sensing cells on the papillae of the tongue. The findings were published in the journal Chemical Senses.
It is thought that the systems that enable us and other mammals to taste and smell are separate, and our brains combine this information so we can experience flavor. While the tongue deals with whether food is salty, sweet, sour, bitter, or umami, our noses provide more detail from smells.
As such, the study calls into question whether the mixing of smell and taste first happens in the brain. Instead, it provides evidence suggesting the process that creates flavor may first happen in the tongue.
However, Dr. Mehmet Hakan Ozdener, senior study author and a cell biologist at Monell Chemical Sense Center, stressed to The Guardian: “I am not saying that [if you] open your mouth, you smell.”
He said in a statement: “Our research may help explain how odor molecules modulate taste perception. The presence of olfactory receptors and taste receptors in the same cell will provide us with exciting opportunities to study interactions between odor and taste stimuli on the tongue.”
To arrive at their conclusion, scientists used genetic and biochemical tests to study human taste cells in a lab. They also used calcium imaging, which showed taste cells react to smells similarly to cells which pick up odor.
Ozdener was inspired to carry out the research after his 12-year-old son asked him if snakes waggle their tongues out of their mouths to smell.
The team hopes the research could help to combat the obesity epidemic, by creating flavor without the need for heaps of delicious yet unhealthy ingredients.
“This may lead to the development of odor-based taste modifiers that can help combat the excess salt, sugar, and fat intake associated with diet-related diseases such as obesity and diabetes,” he said.
The team also hopes their work will shed light on the little-understood olfactory system, which contains around 400 different receptors which enables us to smell.
Earlier this week, a separate team published a study showing humans use their sense of smell to navigate space. The scientists behind the study published in the journal Neuron created a “smellscape” in a room featuring the scent of pine and banana, which participants moved around.
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