Our sense of smell – just like our vision, hearing, and pretty much everything else – is known to get worse with age. However, a new study goes as far as to suggest that an impaired ability to smell in old age could be linked to an increased risk of death.
Recent research by Michigan State University found that older adults with a poor sense of smell have an almost 50 percent increased risk of dying within 10 years. This strange link even seemed to be true among individuals who appeared to be relatively healthy.
These findings might smell a bit fishy, but there’s a growing field of study that’s been looking at the unlikely link between sense of smell and wider health, especially in older people. For example, previous studies have found that an early symptom of Parkinson’s and dementia is a decline in the ability to smell.
Why, exactly, remains a bit of a puzzle, but this new study hopes to edge a little closer to the answer.
"Poor sense of smell becomes more common as people age, and there's a link to a higher risk for death," Honglei Chen, an epidemiologist at Michigan State, said in a statement. "Our study is the first to look at the potential reasons why it predicts a higher mortality."
Reporting in the journal Annals of Internal Medicine, researchers sifted through data on about 2,300 participants between 71 and 82 years old and looked at their ability to detect 12 common smells like chocolate, lemon, onion, and petrol. They then measured their rate of survival 13 years on.
Compared to those with a good sense of smell, people who scored badly on the “smell test” had a 46 percent higher risk of death at 10 years and 30 percent at 13 years. Some of the deaths were related to Parkinson's disease and dementia, as might be expected, but the causes of a large majority of the deaths remain unclear. Respiratory disease and cancer, meanwhile, did not appear to be linked to the sense of smell.
So, what could be behind this link? An editorial to accompany the study notes that the “olfactory nerve is the only cranial nerve that is directly exposed to the environment," suggesting the nose nerves could be especially vulnerable to disruption by health problems and even help doctors to make a diagnosis.
However, the study didn’t look to find a causal link behind the relationship, so the mechanism remains unclear for now. Chances are, there is a whole bunch of other factors at play here. As with any health and epidemiology studies, we should be careful about jumping to conclusions with the findings.
In other words, if your sense of smell isn’t what it used to be, you shouldn’t panic and expect a visit from the Grim Reaper.
“The causation here could be very complicated. One possibility is that poor sense of smell is a sign, perhaps an early sign, of some underlying illness," independent expert Kevin McConway, Emeritus Professor of Applied Statistics at the Open University, commented on the study.
"Another is that poor sense of smell might itself lead to illness, perhaps because poor smell affects how food tastes, and therefore might contribute to poor nutrition which could lead to bad health.
“So should you be concerned about these findings if you feel you have a poor sense of smell? Well, not necessarily," he concluded.