Loss of Smell: an Accurate 'Harbinger of Death'

For aging adults, losing sense of smell is more of a tell that the grim reaper will be paying a visit very soon than any other symptom. That's according to a new study that explains how and why sense of smell is such a crucial indicator of mortality.

The study, recently published in the journal PLOS One, details how being unable to identify smells generally means an elderly patient only has up-to five more years to live.

"Olfaction is a critical, if underappreciated, component of human physiology," the authors of the study wrote.

They explain that our sense of smell is tied to a great number of functions extremely necessary in order to go on with life, including the maintenance of adequate nutrition through appetite and food preferences. Smell also enables the detection of environmental hazards and pathogens, is associated with memory, emotions and intimate social relationships, and is closely linked with key parts of the nervous system.

When a body's sense of smell disappears, it could be argued that the body, if not the mind, has lost its will to live, or just simply understands that the time has finally come to throw in the towel.

But to defend this theory, you need hard facts. That's where the National Social Life, Health and Aging Project (NSHAP), an ongoing home-study of social relationships and health of participants 57 to 85 years old, comes in.

Through NSHAP, the researchers interviewed 3,005 participants and assessed their ability to correctly identify five common odors. A second round of interviews were conducted again in 2010 and 2011 on the 2,565 subjects still living.

Strikingly, of the participants who had failed the first smelling test (failing to identify four to five of the odors), 39 percent had died before the follow-up. In contrast, 19 percent of participants with moderate smell loss and 10 percent of those with a good sense of smell died within the same five years.

The study also assed the reliability of mortality indicators like cancer, heart failure, and breathing difficulty. Amazingly, only damage of an aptly named organ, the liver, proved more accurate than olfactory system failure.

"We believe olfaction is the canary in the coalmine of human health, not that its decline directly causes death," the authors are quick to add. "Olfactory dysfunction is a harbinger of either fundamental mechanisms of aging, environmental exposure, or interactions between the two."