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 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.
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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."
SOURCE: http://bit.ly/2vrDJkP Annals of Internal Medicine, online
April 29, 2019.
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