Decreasing sense of smell can predict death

Whether flowers, baked bread or fresh ground coffee, a decent sense of smell is more than sensory pleasure

Christian Gressner

Realizing that the loss of a sense of smell can act as a bellwether of Alzheimer’s, Parkinson’s and other diseases of the brain, Drs Jayant Pinto and Martha McClintock of the University of Chicago set out to investigate if olfaction is an omen of five-year mortality in their paper Olfactory Dysfunction Predicts 5-Year Mortality in Older Adults.

They asked 3,005 participants aged 57-85 from the National Social Life, Health and Aging Project, a nationally representative sample of older US adults, to identify five commonly recognized scents encased on the tips of felt-tipped pens: fish, leather, orange, peppermint and rose.Five years later, the Olfactory Research Group ran the test again. They found that 39% of adults who had the lowest scores had passed away, compared with 19% with moderate smell loss and just 10% with a healthy sense of smell.

Even after adjusting for age, gender, socioeconomic status and race, the correlation still held true. Nutrition could not explain the findings. Nor could smoking or alcohol use. Even when they controlled for specific diseases, like heart failure, cancer, strokes and diabetes, the relationship between not being able to smell and being more likely to die in five years remained consistent. Only severe liver damage was a stronger predictor of death. The next round of results is due.

SMELL OF DEATH

The declining sense of smell of those tested did not directly cause death but acted an early warning sign, says Pinto, an associate professor of surgery at the University of Chicago and a specialist in sinus and nasal diseases, including olfactory dysfunction. Olfaction acts as “the canary in the coalmine of human health,” he told PROJECT M.

Olfaction is a primal sense connected to ancient, evolutionary parts of the brain. And it is a strong indicator of overall health as it is linked to diverse physiological processes. “Smell is a marker of overall brain function,” says Pinto.

A reduced ability to sniff out odors may signal less regeneration or repair of cells in the body overall, as a healthy sense of smell depends partly on a continual turnover of stem cells (from which other sorts of cell develop) that line the nose. “Olfaction is a marker of cellular resilience. When stem cells stop regrowing, your body is probably becoming obsolete,” says Pinto.

And a worsening sense of smell may serve as a mirror for a lifetime’s exposure to pollution and bugs, he adds.

Moreover, there appears to be link between a limited sense of smell and mortality when other clinical signs of neurogenerative disease aren’t present, says Robert S. Wilson, Rush Alzheimer’s Disease Center in his study Odor Identification and Mortality in Old Age, which found that those older adults with an impaired sense of smell were about 36% more likely to die than those with a relatively good sense of smell.

Smell is probably the most underappreciated of our five senses. Maybe a “smell test” should become as routine as an annual eye or hearing test, particularly if this ancient sense can sniff out impending death. Meanwhile, stop and smell the roses.

Decreasing sense of smell can predict death

Whether flowers, baked bread or fresh ground coffee, a decent sense of smell is more than sensory pleasure

Christian Gressner

Decreasing sense of smell can predict death

Whether flowers, baked bread or fresh ground coffee, a decent sense of smell is more than sensory pleasure

Christian Gressner

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