mortality

Can Sense of Smell Predict Mortality?

The inability to identify scents can be a strong predictor of death within 5 years, says a new study.

“We think loss of the sense of smell is like the canary in the coal mine,” said Jayant M. Pinto, MD, the study’s lead author and an associate professor of surgery at the University of Chicago.
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“It doesn’t directly cause death, but it’s a harbinger—an early warning that something has gone badly wrong and that damage has been done. Our findings could provide a useful clinical test, a quick and inexpensive way to identify patients most at risk,” she said.

In the phase 1 of the study (which is part of the National Social Life, Health and Aging Project), researchers tested 3005 participants (1551women and 1454 men age 57-85) to measure their ability to identify 5 different odors (in order of difficulty): peppermint, fish, orange, rose, and leather. 

After researchers presented participants with the 5 scents, they were asked to choose from 4 possible answers.

The results showed that:

  • Almost 78% were normosmic (having a normal sense of smell) with 45.5% identifying 5 out of 5 odors and 29% identifying 4 out of 5 odors.
  • Almost 20% were hyposmic (moderate loss of smell) and correctly identified 2-3 of 5 odors.
  • The remaining 3.5% were anosmic; 2.4% identified 1 out of 5 odors and 1.1% identified none.

After accounting for the participants’ age, physical and mental health, social and financial resources, education, and alcohol or substance abuse, researchers noticed that performance on the scent test declined with age.

In the second phase follow-up, which took place between 2010 and 2011, the survey team confirmed which participants were still alive. During the 5-year period between study phases, 12.5% or 430 of the original 3005 study participants had died.

Researchers concluded that individuals with greater smell loss when first tested were substantially more likely to have died 5 years later. Further, even mild smell loss was associated with greater risk.

Researchers believe that the decrease in olfactory function could be a sign that a person has an ability to rebuild key components that decline with age.

The complete study is published in the October issue of Plos One.

-Michelle Canales

References:
1.  Pinto JM, Wroblewski KE, Kern DW, et al. Olfactory dysfunction predicts 5-year mortality in older adults. Plos One. 2014 Oct [epub ahead of print] doi: 10.1371/journal.pone.0107541.

2. U Chicago News. Decreased ability to identify odors can predict death. October 2, 2014. http://news.uchicago.edu/article/2014/10/02/decreased-ability-identify-odors-can-predict-death. Accessed October 3, 2014.