Losing your sense of smell could be an early warning sign that you will die within five years, say US scientists.
Almost 40% of older people who failed a smelling test died during that period compared to 10% of those with a healthy sense of smell.
Amazingly, a poor sense of smell predicted mortality better than a diagnosis of heart failure or cancer.
The study, in the journal PLOS ONE, was part of the US National Social Life, Health and Ageing Project looking at men and women aged 57 to 85.
Researchers first surveyed 3,000 people in 2005-06, assessing their ability to identify five distinct common odours one at a time from a set of four choices.
The five odours, in order of increasing difficulty, were peppermint, fish, orange, rose and leather.
In the second survey in 2010-11, the team confirmed which participants were still living.
During that five-year gap, 430 (12.5%) of the original 3005 study subjects had died and 2,565 were still alive.
Thirty-nine per cent of study subjects who failed the first smelling test died before the second survey, compared to 19% of those with moderate smell loss and just 10% of those with a healthy sense of smell.
For those already at high risk, lacking a sense of smell more than doubled the probability of death.
Precisely how smell loss contributes to mortality is unclear but the researchers say olfactory dysfunction is 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.
“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, associate professor of surgery at the University of Chicago.
“It doesn’t directly cause death, but it’s a harbinger, an early warning system, that something has already 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.”
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