The Grapevine

Longevity Measured By Sense Of Smell Spells Bad News For The Noseblind

smell
Mounting evidence points to your sense of smell as the most reliable indication that death may be drawing near. Photo courtesy of Shutterstock

Your hearing and vision are bound to dull at some point, but few of us discuss the age-related woes of losing our sense of smell. Now scientists have evidence we probably should, as a new study finds the risk of death increases substantially as the nose loses its ability to detect unique smells.

Sense of smell is gaining traction not just as a reliable predictor of mortality, but of other precious bodily functions, such as female fertility and memory. For various reasons, ranging from the changing preferences of a woman in search of a mate to the brain’s inability to process sensory information in similar regions associated with mental disorder, researchers are finding the olfactory system leaves much to be understood.

In the latest piece of nose-related science, a team from Columbia University looked at data from 1,169 Medicare beneficiaries, who were asked to smell 40 strips laced with different odorants. After each whiff, they were tasked with answering a multiple-choice question identifying the scent.

Results showed people who performed the worst on the 40-question tests had a mortality rate of 45 percent. Those in the highest-scoring bracket had only an 18 percent mortality rate. To the investigators, this upheld prior findings that suggest something specific about olfaction: Even after controlling for mental burden and dementia, the loss of smell remained a consistent predictor of early death.

There are some limitations to studying death via a failing nose. At least in terms of the recent study, says Dr. Davangere Devanand, lead author and professor of psychiatry at Columbia, the age group they tested still leaves room for uncertainty. “This was a study of older adults — the question that remains is whether young to middle-aged adults with impaired smell identification ability are at high risk as they grow older,” Devanand said in a press release.

More generally, scientists can only infer that the nose has predictive powers; it doesn’t wield a causal influence. Sense of smell is more like the canary in the coal mine, who dies first because it is more sensitive to some other, generally more worrisome, cause of death.

But as the tools for analyzing brain science sharpen, researchers will likely have more power in determining the mechanism that gives the nose its unique ability. More importantly, they’ll be able to use that information to effect change, potentially even delaying death.

Source: Devanand D, Lee S, Manly J, et al. Olfactory identification deficits and increased mortality in the community. Annals of Neurology. 2015.

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