死亡的味道

How's your sense of smell?

If the answer is "poor" then this might be a bad sign, because a new studyfrom the US has shown that older adults who fail a smell test are significantly more likely to be dead within 5 years compared with less nasally-challenged individuals.

Jay Pinto, from the University of Chicago, tested over 3000 over 55s on their ability to correctly identify rose, leather, fish, orange, and peppermint smells. Following them up, of those who failed the smell test, nearly half were dead 5 years later.

"We think this is the olfactory equivalent of the coalmine canary," says Pinto. "Among the individuals we studied, regardless of their age or sex, 39% of those with a poor performance in our smell test were dead within five years."

The underlying reason for the results, published this week inPLoS One, isn't known. "The smell sense regenerates itself through life from stem cells," explains Pinto. "So the failure of smell discrimination might be a sign that the regenerative and repair capacity of the body as a whole has failed, leading to physiological decline."

The idea is an attractive one, but there are other possible explanations, such as the loss of smell being related to underlying neurological diseases which ultimately kill the patient.

"At the moment we know only that the patients died, and not the cause of death," points out Pinto. "We're going to be looking at whether there are any specific disease associations next."

Asked whether the relationship might be down to something as simple as poor smell sense causing poor food enjoyment and under-nutrition, Pinto dismisses this. "We looked at that. There was no evidence in our interviews with the patients [at the time of the smell test] linking poor smell and poor diet."

The findings are significant since they may offer doctors an early warning sign, just like to coalminer's canary, that a patient's health is in decline and that intervention is needed. "It's a cheap test that takes 3 minutes," says Pinto.