Want to know how long you'll live? How well your sense of smell is might be able to give you a clue.

In a study published in the journal Annals of Neurology, researchers showed that an individual's ability to identify certain scents and odors may impact how long they will live. The study involved 1,200 subjects, 1169 of which were Medicare beneficiaries. All aged 65 years old and above, they were made to identify 40 scents and odors by scratching and sniffing odorant strips and then choosing the best answer to identify what they had smelled from a 4-item list.

A 4-year follow-up period was employed and results showed that 45 percent of those with the lowest scores had already died, compared to the 18 percent mortality rate of those with the highest scores.

According to the researchers, every wrong answer increased the odds of an individual succumbing to an early death. Subjects who logged the lowest scores were found to have 2.5 times more risk of dying early than those with the most correct answers.

Why a poor sense of smell may be an indicator of a short life span is not clear. Davangere Devanand and colleagues, however, suggest that a poor sense of smell brings about early death through a number of reasons.

First, it puts individuals in higher risk of physical danger. Not smelling a gas leak, for instance, poses a lot of threat to life. Kitchen fires have claimed lives that could have been otherwise saved if a gas leak was spotted early.

Second, it doesn't warn people that they may be possibly consuming spoiled food, which can make them sick.

Third, a drop in smelling ability may be indicative of damage to the olfactory nerve, whose health may be a sign of overall health. As such, if the olfactory nerve stops working, the rest of the body and the brain may soon follow.

Lastly, it is possible that pollutants, poisons and infections inhaled first damage the sense of smell before attacking the rest of the body.

"This was a study of older adults [though]," said Devanand, the lead author of the study.

To truly determine if sense of smell can be indicative of life span, further research will have to be carried out including young to middle-aged subjects.

Richard Doty, Richard Mayeux, Yaakov Stern, Arjun Masurkar, Nicole Schupf, Howard Andrews, Jennifer Manly and Seonjoo Lee also contributed to the study.

Photo: Dennis Wong | Flickr

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