According to the Oxford English Dictionary, the nose is “the part projecting above the mouth on the face of a person or animal, containing the nostrils and used for breathing and smelling.” And the description admittedly doesn’t sound very special. But this central facial feature does so much; it can even potentially sniff out life-threatening health conditions that you didn’t know you have.
Before 2014 scientists had estimated that the human nose could discern about 10,000 scents. However, researchers held onto a feeling that the sniffer could actually distinguish many more than that; they just needed a testing method to prove the theory. So in 2014 a team presented their research, which had been conducted with the help of odorous molecules, and it revealed something spectacular about our noses.
After all, it turns out that the human nose can decipher many, many more than just 10,000 scents. The updated research found that that figure was closer to one trillion smells, at least. Indeed, the study’s co-author Andreas Keller told Nature that the research proved a common conception about humans to be untrue. “My hope is that this helps to dispel the myth that humans have a bad sense of smell,” he said.
Beyond that stunning statistic, though, the nose has a slew of other remarkable abilities that revolve around its sense of smell. Namely, it can sniff out potentially dangerous health conditions. And the research has shown, for starters, that a struggling sense of smell can be a signifier for premature death.
More specifically, a study by the National Social Life, Health and Aging Project brought in more than 3,000 study subjects, all of whom were between the ages of 57 and 85. Researchers had these participants identify five common scents: leather, orange, peppermint, fish and rose. And the more that a person wrongly labeled, the more they seemed to be suffering from a reduced sensitivity to scents.
Then, five years after that exercise, researchers caught up with their study’s participants to see if they would do the five-scent smell test one more time. But since the start of their study, 430 people – or 12.5 percent of their initial research pool – had passed away. When the team looked at those people’s results from the first exam, they realized that 39 percent of them had failed.
On top of that, the researchers’ data showed that only 10 percent of the deceased had passed their original smell test. And with that result in mind – as well as the fact that nearly 40 percent of the dead failed – experts could say that those who lost the ability to smell were four times more likely to die within five years than their more discerning counterparts.
The research team also found that one’s inability to smell proved to be a more accurate predictor of death than serious health diagnoses, including cancer, lung disease or even heart failure. Severe liver damage was the only other condition as accurate as smell loss in predicting a fatality, in fact.
And as for why this phenomenon presented itself, researchers first noted that smell loss doesn’t directly cause death. It could, however, indicate one of two issues that show that a person’s health is in decline. First, the olfactory nerve houses all the body’s receptors for smell, and it’s also the sole part of the nervous system that refreshes itself with stem cells throughout a person’s life.
So when a person starts to lose their sense of smell later in life, it may be because their olfactory nerve has stalled in its production of new cells that can discern between odors. And, once this happens, it may signify a turning point for a person’s body – that can no longer repair and regenerate itself.
And another potential reason for the link between smell and early death is the fact that the olfactory nerve comes in contact with outside air – and it’s the only piece of the nervous system to do so. Hence, a loss of smell could indicate that a poisonous substance or pathogen has made its way toward the brain and will later cause death.
What’s more, a separate Harvard Medical School study found links between an inability to smell and a more specific diagnosis: Alzheimer’s. The disease eventually causes memory loss and severe behavioral changes, and it can go on to cause dementia. Before that, though, a person might notice their sense of smell fading away.
And Harvard researchers linked the patients’ inability to smell back to one of the triggers of Alzheimer’s itself. According to the Alzheimer’s Association, “Scientists believe [the] disease prevents parts of a cell’s factory from running well.” They still do not know the cause of this malfunction, but dysfunctional cells eventually die off and damage the brain irreparably.
Two structures appear in a person’s brain with the onset of Alzheimer’s – plaques and tangles – and both have the potential to destroy cells. And a type of protein called beta-amyloid makes up the plaque, which fills up gaps between nerves. Meanwhile, tangles build up inside of the cells, and a protein called tau comprises their twisted form.
According to the Harvard Medical School study, though, it’s the amyloid plaque that has a direct link to a person’s sense of smell. Namely, study subjects who performed poorly on a smell-identification test had more of the plaque present in their brains than their healthier counterparts. And they also had more destroyed cells within the organ too.
Therefore, researchers believed, the plaque had damaged cells, including the ones responsible for a person’s sense of smell. And as those particular cells got destroyed by plaque, Alzheimer’s patients would lose the ability to identify aromas. Consequently, that lack of smell could precede the onset of the disease.
Alcoholism stands as another disease that can beget a lack of smell over time, although it comes as an offshoot of another alcohol-related diagnosis. And Korsakoff’s syndrome affects alcoholics, typically causing them to feel severely disoriented and to suffer from memory loss as well.
Research completed as long ago as the 1970s found links between Korsakoff’s syndrome and problems with the olfactory system. And more recent research showed that the same problems exist in those with Korsakoff’s syndrome who do not have further complicating factors, such as amnesia or dementia.
Clinical neuropsychologist and first author of the University Clinics of Innsbruck’s study, Claudia I. Rupp, tested both alcohol-dependent and healthy subjects with odor-dispensing devices, one nostril at a time. She told EurekAlert, “A large number of patients, 57 percent, had hyposmia, a diminished sense of smell.”
And Rupp added that other causes had been ruled out. Only alcohol could have caused the diminished sense of smell. “Impairments in odor sensitivity, discrimination and identification abilities were not related to age, gender, or duration of abstinence from alcohol; nor were they attributable to smoking habits or general cognitive abilities. Rather, the deficits appear to be alcohol related,” she said. Alcoholism could, therefore, cause the deterioration of one’s sense of smell. So if you or a loved one loses the ability to discern different scents, it could indicate a heavy dependence on booze.
In another research study, scientists relied on a similar smelling test to see if a different disorder could cause the same effect. And this time around, researchers brought in 136 people without health issues and 54 who had schizophrenia. Yes, they wanted to see if the latter group had any differences in their olfactory system traceable to their disorder.
So each participant took an exam that featured 40 scratch-and-sniff scents with a multiple-choice list of answers for each aroma. Those with schizophrenia could not identify multiple scents on the exam that the control group could. And this consequently made an out-of-tune sense of smell a potential sign of the disorder.
Perhaps more interestingly, though, schizophrenics could easily discern the smell of pizza, clove and wintergreen. And these are aromas that typically baffle test-takers with Parkinson’s disease. Nevertheless, those with Parkinson’s and schizophrenia still miss the same amount of answers on the test.
To researchers, this meant that both the mental health disorder and the neurodegenerative disorder caused cognitive deficits that affected a person’s ability to smell. And a change in this sense could indicate the start of schizophrenia too. Separate research has shown that smelling and tasting things differently are precursors to the disorder.
Another scent-related precursor to schizophrenia and other serious health issues is phantosmia. A person suffering from phantosmia typically picks up on an unpleasant aroma, although the occasional case will feature a nice-smelling, albeit unreal, scent. And the most common odors include burning rubber, cigarette smoke, mold, rot and burnt toast.
In most cases, phantosmia fades away by itself, so it’s not a huge cause for concern. And in other cases, though, picking up on an illusory scent can signal that something worse is happening. On the one hand, phantosmia can mean that the nasal cavity or the nose has a problem ranging from nasal polyps to allergies to chronic sinus infections. It can also point to something more serious, such as a tumor.
Alternatively, these seemingly non-existent aromas could arise because of a brain-related issue. It may be that the organ may not be properly understanding or processing smells. Hence, a person may have suffered or continue to suffer from schizophrenia. And other possibilities include trauma to the head, Parkinson’s disease or depression.
And in terms of the latter, doctors – including the University of Nebraska Medical Center’s Donald Leopold – have found that phantosmia can cause depression and even suicide when the illusive scents become too pervasive. “Approximately half of my patients… have at one time considered suicide because of the hopelessness of living a life where all food smelled like spoiled meat or worse,” he wrote in Chemical Senses.
There’s also an ongoing link, at least informally, between phantosmia and stroke. And some call it the “burnt toast rumor,” according to Iran Daily. General practitioner Dr. Adam Simon said, “There’s a popular myth that smelling burnt toast is a sign… that you’re having a stroke. This isn’t true.”
And Simon did, however, say that because a stroke can “affect any area of your brain… it’s possible that your sense of smell can be affected.” Therefore, the potential of a phantom burnt-toast smell arising is possible, but it’s not the only potential pre-stroke scent out there as far as phantosmia is concerned.
Similarly, nonreal scents can waft in the build-up to a migraine, too. Regular sufferers of these moderate to severe headaches know that before the pain strikes they can experience auras. Typically, an aura is solely a visual side-effect: a person might see lights flashing, or they may notice that they have blind spots.
And an aura might also manifest as numbness or a tingling in the body. Some people even notice that they cannot understand others who speak to them, or the aura makes it difficult for them to talk. These sensory changes affect roughly 30 percent of people who have migraines regularly.
Surprisingly, an aura can also bring with it phantosmia, although such a side-effect had gone unrecognized before 2011. And in that year, a study by New York’s Montefiore Headache Center revealed a small-but-present link between the olfactory hallucinations and an impending migraine. Senior researcher Matthew S. Robbins told Reuters that “the most common was of the burning or smoke variety.”
Second to that, affected migraine sufferers reported smelling something like garbage or sewage – the scents of decomposition, apparently. And a few patients did report that they picked a more pleasant aroma, including coffee and oranges. Additionally, there was a single case of a person smelling foie gras pre-migraine.
And according to Robbins, auras occur because of something called cortical spreading depression. In this process, you see, the brain’s nerve activity slows after a period when it’s boosted. But why do more people have vision-related symptoms than smellable ones? That’s because the brain devotes much more space to vision centers than it does to the olfactory nerve.
Fortunately, this link does provide some solace to those who experience a phantosmia. Not every unexpected aroma is the sign of a serious health condition, mind you. If a migraine precedes the smell-based symptoms, Robbins said, then a person might not need “extensive medical workups.” But he did reiterate that olfactory hallucinations arising sans headache did require a check-up.
And although much of our bodies’ nose-based detective work relies on a sense of smell – or lack thereof – some people can uncover an issue based on the health of the nose itself. For example, there’s a link between hypertension, or high blood pressure, and nosebleeds. People typically consider more obvious causes when it comes to nosebleeds, including trauma or inflammatory diseases.
Nonetheless, the cause and effect of hypertension and nosebleeds aren’t what they seem, though. One study found that patients with nosebleeds suffered from more attacks if they had high blood pressure. But scientists could not hone in on a definite link between the two afflictions. Plus, in some cases, nosebleeds cause hypertension – not the other way around.
And in the latter scenario, those who suffer from regular nosebleeds start to feel stress awaiting the next one. That tension, in turn, causes blood pressure to spike. Therefore, doctors can assuage the effects with therapy to reduce stress, lower blood pressure and shift focus from nosebleeds.
With all of this in mind, it’s clear that the nose is more than just a facial feature. That’s right: it can pick up on phantom scents that signify an underlying health issue. And its inability to sniff out different aromas can tell us the same information. So, next time you smell something strange, think twice about ignoring it – as your nose could be telling you something vital about your health.