A fading sense of smell as we age may be an indicator of our remaining lifespan, researchers say, with those having a poor sense of smell more likely to die within 5 years.

A study involving 3,000 older American adults discovered those who could not detect odors such as peppermint, oranges, roses or leather were around three times as likely to die in coming years as compared to those who still retained a sharp sense of smell.

During the 5 years after they were surveyed, 39 percent of people with poor sense of smell died, versus 19 percent of those with moderate smell loss and 10 percent of those who retained an intact sense of smell.

The failure to sense odors, known medically as anosmia, proved to be a better predictor of approaching death than did major diseases including heart or lung disease or cancers, the researchers reported in the journal PLOS One.

"We were pretty surprised it was such a strong predictor," says study leader Dr. Jayant Pinto, a University of Chicago specialist in nasal disorders.

Exactly how smell, or the lack of it, is linked to lifespan is unclear, the researchers say.

It's possible a reduced sense of smell could be evidence of the body's declining ability to regenerate or repair cells generally, they suggest.

A declining sense of smell could also indicate a lifetime of exposure to pollution, toxins and disease, they add.

"We think loss of the sense of smell is like the canary in the coal mine," Pinto says.

"It doesn't directly cause death, but it is a harbinger, an early warning system that shows damage may have been done."

A loss of the ability to smell is not necessarily a reason to panic, he says, since many conditions such as allergies, a severe cold or sinus problems can also negatively impact the nose's ability to detect odors.

"People shouldn't be too worried, but if problems persist they should speak to their physicians," he says.

Pamela Dalton, a scientist at the nonprofit Monell Chemical Senses Center in Philadelphia, who was not involved in the study, agrees that people shouldn't get too anxious about a loss of smell.

"There's no need for people to be scared," she said, but did acknowledge the findings are significant, agreeing with Pinto that smell detection problems can in some cases be a warning of health issues to come.

Still, Pinto says, it underlines how important our sense of smell is in our lives, even if we don't give it much thought.

"Of all human senses," he said, "smell is the most undervalued and underappreciated -- until it's gone."

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