Older adults who have trouble distinguishing common scents could be more susceptible to death within the next five years of their life, as compared to their peers who can stop and smell the roses. Literally.

The results of a new study on olfactory dysfunction shows that adults in their later years who cannot tell the difference between smells such as peppermint, fish and leather were three times more likely to die in the next five years.

The researchers say that anosmia, or the inability to decipher different smells, is not a cause of death. Rather, it is one of the strongest predictors of death -- far more accurate than the existence of cancer, heart disease or lung problems, they say.

"We think loss of the sense of smell is like the canary in the coal mine," says lead researcher Jayant Pinto of 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."

The researchers gathered data from the National Social Life, Health and Aging Project, which surveyed 3,005 men and women aged 57 to 85 on their ability to smell. Participants were given five felt-tip pens that carried five different scents: rose, leather, orange, fish and peppermint. They were then asked to identify the smells. The participants were grouped according to their scores, with the "low" group getting only one smell correct, the "moderate" group scoring two to three, and the "healthy" group getting all or almost all scents right.

Five years later, the investigators conducted a second survey and found that 39 percent of those in the "low" group had died, as opposed to the 19 percent and 10 percent in the "moderate" and "healthy" groups. The researchers also accounted for other risk factors, such as smoking, drinking, major diseases and the participants' cognitive skills, and they found that subjects who had anosmia still had the greatest risk.

"The sense of smell is a little underappreciated -- it plays a very important part in everyday life," Pinto says. "Our findings could provide a useful clinical test, a quick inexpensive way to identify patients most at risk."

The researchers have no explanation as to what causes the link between a deteriorating sense of smell and longevity, but Pinto offers the theory that anosmia could be caused by the human body's diminishing ability to regenerate new cells in the nose. He also said that it could signal years of exposure to harmful chemicals that pollute the air.

Insight into the sense of smell and longevity was published in PLOS ONE.