A declining sense of smell among older adults may predict death in five years' time, says a new study published Wednesday in the journal, PLOS One.

A study involving 3,005 older American adults found out that failure to pass a simple smelling test makes a person three times more likely to die within five years than those who showed a healthy sense of smell.

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Participants were tracked for five years, in which time 39 percent that showed decreased ability to identify odors died compared to the 19 percent that presented only moderate smell loss and 10 percent that had a completely healthy sense of smell.

The test involved identifying five different common odors, namely fish, peppermint, rose, orange and leather. Participants were also checked for their age, mental and physical health, education, social and financial status, and history of substance abuse.

As was expected, performance in the test declined with age. 

Even a mild loss of the sense of smell was associated with lower life expectancy. Of those tested, 430 or 12 percent were confirmed dead five years after the initial testing.

The inability to sense odor proved to be a better indicator of approaching death than did other major diseases such as lung disease, cancer or heart failure, researchers said. 

For those already diagnosed with these conditions, a poor sense of smell more than doubled the risk of death in the coming years.

But experts say this is no cause for panic.

"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," said Jayant M. Pinto, MD, the study's lead author and an expert in nasal disease treatment.

The findings may provide a quick and easy clinical test to identify people at risk, he said.

The research was part of the National Social Life, Health and Aging Project (NSHAP) which looks into health and social relationships using a nationally representative sample of men and women between ages 57 to 85.

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