Your ability to detect five scents in old age can predict how long you'll live

Images (clockwise from top left): Ortis, leungchopan, Kazyavka, Top Photo Corporation, juniart/Shutterstock

Older adults who struggle to identify five common smells are more likely to die in the next five years than their peers, according to a new study led by the University of Chicago.

The scientists tested 3,005 men and women aged 57 to 85 on their ability to detect five smells: rose, orange, leather, fish and peppermint.

Almost 40 percent of those who couldn’t identify the simple scents died over the next five years, compared to 10 percent who had a healthy sense of smell and 19 percent who only had moderate smell loss.

This means that the loss of smell is a bigger predictor of death within five years than most chronic diseases, the researchers explain in PLOS ONE, where their results were published.

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

The large-scale study was conducted in people’s homes as part of the US’s National Social Life, Health and Ageing Project (NSHAP), and involved “Sniffin’Sticks” - odour-dispensing devices that look like a felt-tip pen.

The scents were presented in order of difficulty to identify - peppermint, fish, orange, rose and then leather - and the participants had four options to select from.

While the large majority of those tested were able to identify four or five of the odours, 3.5 percent were labelled “anosmic”, which means they could only detect one or none of the scents.

The researchers then followed up with who was still alive five years later. As Nicholas Bakalar explains over at the New York Times:

"They controlled for many factors — age, sex, socioeconomic status, smoking, alcohol intake, education, body mass index, race, hypertension, diabetes, heart attack, emphysema, stroke and diet. But still, people who could not detect the odours were more than three times as likely to die within five years as those who could. The lower their scores on the odour test, the more likely they were to die. Only severe liver damage was a better predictor of death."

Of course, this is not a case of smell-loss causing death, but the scientists are now investigating the link further.

“A decrease in the ability to smell may signal a decrease in the body's ability to rebuild key components that are declining with age and lead to all-cause mortality,” said team leader Martha McClintock in the press release.