By Andrea Hargraves 
Barry Smith was diagnosed with Parkinson’s disease at the age of 50-18 years before that, however, he developed very strange and permanent symptoms.
One day, he discovered “a strong smell of smoke, like burning wires,” he said. Since then, he has not smelled anything.
At the time, Smith’s doctor was disappointed, and attributed the loss of smell to scuba diving, because deep diving can sometimes cause problems with the sense of smell.
I hope the doctor is right.
Loss of smell can have more serious causes beyond scuba diving, and in Smith’s case, this was proven to be true.
In today’s world, most people automatically attribute loss of smell to Covid-19 disease, but it is also a common symptom of neurodegenerative diseases, including multiple sclerosis, Parkinson’s disease and Alzheimer’s disease.
A survey found that up to 38% of people with multiple sclerosis and about half of older adults diagnosed with dementia showed signs of loss of smell before five years. In Parkinson’s disease, between 45% and 96% of patients have an impaired sense of smell.
For years, loss of smell – or loss of smell, as it is also known – has been largely ignored as a marker of diseases like Parkinson’s, but now some scientists believe that using it as a diagnostic tool can have major advantages.
Diseases like Parkinson’s appear in the olfactory region of the brain long before other regions, and this is thought to be the reason why Smith lost his sense of smell 18 years before his first tremor.
An accurate smell test could have identified the disease nearly two decades before its official diagnosis, and it could have given it more time to slow its progression.
Several initiatives are developing tests that can use scent to help diagnose neurodegenerative diseases.
Predict-PD is one of those initiatives. Alastair Noyce, clinical professor at Queen Mary University in London who is leading the project, has developed a scent test called Scratch and Sniff.
A study in the elderly showed a relationship between a person’s olfactory ability and life expectancy – Image: FABRICE / GETTY IMAGES by BBC
It’s a quick test that presents a patient with six odors we typically encounter throughout the day, based on a broader list of 40 scents.
The hope is that the data collected can be used to predict who will develop Parkinson’s disease, which could lead to new early treatments that could either prevent or slow disease progression.
And with a percentage of 0.45% to 3.4% of individuals (depending on the test) seemingly unaware of their loss of smell, tools like Predict-PD can help people recognize it.
The problem is that these tests are currently very expensive.
“A standard odor test costs 25 pounds (191 RUB), but only a few cents are produced,” says Noyce.
While the cost may not be a barrier to the many private clinics that use olfactory tests as a diagnostic tool, it does restrict their usefulness to public health systems with limited resources.
It is clear that the decreased sense of smell does not only develop as a result of neurodegenerative diseases. About 19% of the population suffers from some type of olfactory dysfunction, with 0.3% losing their sense of smell (anosmia) and 19.1% having an impaired ability to detect smell (decreased sense of smell).
Recent studies have shown that loss of smell may be related to mental health conditions, such as depression, schizophrenia, and dystonia, a movement disorder in which a person’s muscles contract uncontrollably.
A 2016 study found that men (not women) who had depressive symptoms also tended to have a foul odor, while those who felt lonely were not generally good at identifying different scents.
Other research has linked a decreased sense of smell to an increased mortality rate, indicating that it may be a “warning sign” of aging or disease.
A study of more than 2,200 people between the ages of 71 and 82 showed that those who had a bad smell had a 46% higher risk of death in a ten-year period compared to those with a normal odor.
But how can smell have such a strong link to our health?
Carl Philpott, professor of rhinology and olfaction at the University of East Anglia, UK, thinks there may be a relationship with what we eat.
According to his research, “a third of patients with loss of smell eat too much, and another third of patients eat little,” he said.
Since healthy eating is one of the pillars of good health, it is easy to see why the death rate has increased.
Philpott says that “our sense of smell accounts for more than 70%” of the flavors we experience (although the exact percentage is disputed), which may explain why losing this sense affects a person’s appetite.
This fits with the personal experiences of Clara O’Brien, a freelance clinical neuropsychologist who assists individuals diagnosed with neurological diseases and traumatic brain injuries.
“Smell plays an important role in a patient’s life, and many people lose the pleasure of activities that are an essential part of their daily routine,” she says, explaining that people close to their patients who suffer from loss of smell report that they have changed their behavior, becoming more intrusive, upset or withdrawn.
Honglei Chen, a professor of epidemiology and biostatistics at Michigan State University in the USA, identified another reason why odor leads to an increased mortality rate – that a decreased sense of smell is associated with increased exposure to adverse environments.
If you have a sense of smell, think of times when you were on the road when you smelled the smoke from the car exhaust, and pressed your stride to get away. In this case, the person unable to smell continues to inhale the toxic smoke.
Smith recounts how he once spent hours in his room, filled with smoke from the neighbors’ fireplace, but did not notice until his wife entered.
At the nervous level, a lack of sense of smell can lead to permanent changes in the formation of the brain.
The areas of the brain involved in the sense of smell, such as the olfactory bulb and the piriformis cortex, are contracted, as are the less visible areas, such as the anterior cingulate cortex, which is important for motor control and rational thinking, and the limbic cortex, which is central to emotional processing.
The good news is that areas of the brain that shrink due to loss of the sense of smell can grow back if the person regains that sense.
When this happens, the olfactory bulb, piriform cortex, anterior cingulate cortex, and limbic system expand, and a person’s diet improves.
This means that odor restoration treatments can be a very effective technique. Currently, researchers are developing technologies that will allow this.
Thomas Hamill, who directs the Smell and Taste Clinic at the University of Dresden in Germany, invented a technique called “smelling training”.
Smell patients predict the harmony of scents, combining scents from four scent classes, usually rose, clove, eucalyptus and lemon.
The patient should smell the harmony for 10 minutes, twice a day for three months.
Although this technique does not work for everyone, it has been shown to be effective in improving olfactory capabilities in 40% of patients.
Treatments like Hummel target people who experience loss or odor loss due to a number of conditions, be it Coronavirus 19 or neurodegenerative diseases.
There are also medications available to restore your sense of smell, but they are not common, as these drugs can have side effects, and scent training is not.
However, new treatments are needed for the 60% of patients who do not respond to olfactory training.
There are other treatments being developed for those who have lost their sense of smell. One of them is electrical stimulation: stimulation of a specific area of the brain using electrodes placed on the surface or surgically implanted.
These electrodes lead to changes in brain activity, which in turn can improve a patient’s sense of smell.
For example, electrical stimulation in the nose has been shown to increase the proliferation of olfactory receptor cells, which are the cells responsible for odor.
Stimulating the areas of the brain responsible for the sense of smell can lead to an improvement in this sense, because one of the ways in which olfactory training is effective, increases activity within the olfactory areas of the brain.
Joseph Kakmak, assistant professor of anatomy at the University of Otago, New Zealand, explains that these olfactory neurons involved in the sense of smell also have limbs in areas of the brain associated with memory and navigation, suggesting that protecting these neurons could lead to benefits for memory. .
Cakmak is currently working on a device that can be used as a pair of “glasses” to stimulate the olfactory nervous system, with the ability to relieve symptoms or suppress the spread of diseases such as Alzheimer’s and Parkinson’s.
Early modeling work showed that a person’s sense of smell can improve by receiving a directed electrical current of one milliampere – equivalent to about two to three thousand of the energy stored in a standard AA battery.
Clinical trials are set to begin in late 2021. If effective, we will one day be able to use electrical devices to protect our sense of smell.
Meanwhile, this long-forgotten meaning may merit more attention.