Nose knows when death is imminent, smell study suggests

Sense of smell is the canary in the coalmine of human health, say U.S. researchers, who have found that difficulty identifying particular scents is linked to an increased risk of death.

A new study of more than 3,000 people found that participants with the poorest sense of smell, also called olfactory dysfunction, had a risk of death three times greater than those with a normal sense of smell.

That was even after taking into account other factors, including age, gender, nutrition, mental health status, a history of smoking or alcohol abuse, and other health issues.

Olfactory dysfunction was an independent risk factor for death, stronger than several common causes of death, such as heart failure, lung disease and cancer, the researchers concluded, indicating that this evolutionarily ancient special sense may signal a key mechanism that affects human longevity.

The study was published Wednesday in the journal PLOS One.

For their research, scientists at the University of Chicago studied 3,005 adults between the ages of 57 and 85.

The participants were each asked to identify five scents that had been placed in felt-tip pens: rose, leather, orange, fish and peppermint.

The researchers followed up with the participants five years later.

They found that 39 per cent of older participants with olfactory dysfunction were dead, compared to just 10 per cent who had a normal sense of smell.

The researchers say that the sense of smell is unique compared to other senses in that it relies on stem cell turnover to function properly. A deteriorating sense of smell may indicate a break down in the cell regeneration process, either due to age or the effect of ongoing exposure to environmental toxins.

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Nose knows when death is imminent, smell study suggests