Loss of smell may be predictor of death in older adults

Being unable to smell the roses may be far more dire than simply missing out on one of life's pleasures.

In older adults, it could be a predictor of increased risk of death within five years.

In a study of more than 3,000 people aged 57 to 85, 39 per cent of subjects who failed a simple smelling test died within five years, according to results published in the journal PLOS One.

That compared with a 19 per cent death rate within five years for those with moderate smell loss, and 10 per cent for those deemed to have a healthy sense of smell.

"Compared to a person with a normal sense of smell, a person with an absent sense of smell has three times greater risk of dying within a five-year span," says the study's lead author Dr Jayant Pinto of the University of Chicago .

"What this tells us is your sense of smell is a great indicator of your overall health," says Pinto, who specialises in genetics and treatment of olfactory and sinus disease.

He likens the loss of smell to a canary in a coal mine.

"It doesn't cause death, but it's an early warning that something has gone badly wrong."

The smell test was conducted in 2005 using 'Sniffin' Sticks', which resemble felt-tip pens, that were loaded with five different odours: peppermint, fish, orange, rose or leather.

Nearly 78 per cent of those tested were able to identify at least four of the five scents and so classified as having normal sense of smell. Almost 20 per cent got two or three of the scents right, while the remaining 3.5 per cent could correctly identify one or none of the five, the researchers report.

The researchers conducted interviews to adjust for variables and risk factors, such as age, smoking, alcohol use, overall health and socioeconomic status.

In 2010 and 2011, the team confirmed which participants were still alive. During the five years, 430 of the 3005 subjects, or 12.5 per cent, had died.

Those with greater smell loss when first tested were substantially more likely to have died five years later.

"It predicted it quite strongly," says Pinto.

In fact, olfactory dysfunction was better at predicting mortality than a diagnosis of heart failure, cancer or lung disease. Only severe liver damage was a more powerful predictor of death, they found.

The researchers note that a healthy olfactory system has stem cells that self-regenerate.