Parkinson’s Smell Test Explained By Science
A Scottish woman who astonished doctors with her ability to detect Parkinson’s disease through smell has helped scientists find what causes the odour.
Researchers in Manchester said they had identified the molecules on the skin linked to the smell and hope it could lead to early detection.
The study was inspired by Joy Milne, a 68-year-old retired nurse from Perth.
She first noticed the “musky” smell on her husband Les, who was years later diagnosed with Parkinson’s disease.
Joy, who has worked with the University of Manchester on the research for three years, has been named in a paper being published in the journal ACS Central Science.
She has also been made an honorary lecturer at the university because of her efforts to help identify the telltale smell.
The research revealed that a number of compounds, particularly hippuric acid, eicosane, and octadecanal, were found in higher than usual concentrations on the skin of Parkinson’s patients.
They are contained in sebum – the oily secretion that coats everybody’s skin, but which is often produced in greater quantity by people with Parkinson’s, making them more likely to develop a skin complaint called seborrheic dermatitis.
Lead author Prof Perdita Barran, from the school of chemistry at the University of Manchester, told BBC Scotland: “What we found are some compounds that are more present in people who have got Parkinson’s disease and the reason we’ve discovered them is because Joy Milne could smell a difference.
For Some Smell Test May Signal Parkinsons Disease Up To 10 Years Before Diagnosis
The American Academy of Neurology is the world’s largest association of neurologists and neuroscience professionals, with 36,000 members. The AAN is dedicated to promoting the highest quality patient-centered neurologic care. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as Alzheimer’s disease, stroke, migraine, multiple sclerosis, concussion, Parkinson’s disease and epilepsy.
Research Behind The Smell Test For Predicting Parkinson’s Disease
In a study in Neurology, the sense of smell of over 2500 healthy people was evaluated in 1999-2000. These participants were of the average age of 75 and all lived in the metropolitan areas of Pittsburgh, Pennsylvania and Memphis, Tennessee.
Their sense of smell was examined using the Brief Smell Identification Test . In this test, participants first scratched and smelled 12 different odors. They then had to identify a variety of smells like cinnamon, lemon, gasoline, soap, and onion from four multiple-choice answers.
Several data tools were then used to identify people who developed Parkinson’s disease through August 31st, 2012.
Results revealed that during an average follow-up period of 9.8 years, 42 incident cases of Parkinson’s disease were found, and with that, a link was found between a poor sense of smell and a higher risk of Parkinson’s. This means that people who had the poorest sense of smell had the highest risk of developing Parkinson’s disease.
Interestingly, when the study was broken down into race and gender, the link was strongest in Caucasian participants, as compared to African-American participants, and in men, as compared to women.
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Smell Loss As A Potential Diagnostic Tool
While there is no treatment for smell loss, this symptom is valuable in research toward earlier diagnosis and therapeutic intervention.
Early detection is a crucial step to understanding the causes of and developing better treatments for Parkinson’s disease . Even before the typical tremor and slowness of movement occur, it may be possible to detect early changes in the brain and symptoms that are associated with PD.
The Michael J. Fox Foundation’s landmark study, the Parkinson’s Progression Markers Initiative , is studying people with smell loss. Some people who enrolled in PPMI with only smell loss have since developed Parkinson’s disease. By looking back at the brain scans and blood tests those volunteers contributed before their Parkinson’s diagnosis, scientists can understand what is happening in the earliest stages of the disease. That information could lead to early diagnostic tests and treatments to slow or stop Parkinson’s progression, perhaps before tremor or slowness begin.
The medical information contained in this article is for general information purposes only. The Michael J. Fox Foundation for Parkinson’s Research has a policy of refraining from advocating, endorsing or promoting any drug therapy, course of treatment, or specific company or institution. It is crucial that care and treatment decisions related to Parkinson’s disease and any other medical condition be made in consultation with a physician or other qualified medical professional.
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Sensitivity And Specificity Of Olfactory Testing In Differentiating Pd From Non
The sensitivity and specificity of olfactory testing in discriminating between sporadic PD patients and controls or some other forms of parkinsonism equals or exceeds that of other biomarkers, including SPECT and PET imaging of the DA transporter . In one study of 180 PD patients and 612 non-PD controls, the sensitivity and specificity of the UPSIT in distinguishing between male PD patients and controls under the age of 61 years was 91% and 88%, respectively . For women of the same age, the corresponding values were 79% and 85%. The sensitivity and specificity of this test for those 61 to 70 years of age were 81% and 82% for men and 80% and 88% for women. found the overall sensitivity and specificity of the UPSIT in distinguishing between PD and vascular parkinsonism to be 86% and 89%, respectively. When the data were divided into two age categories , the sensitivity and specificity values were 100% and 86% and 86% and 80%, respectively. Similar sensitivity and specificity estimates have been noted by others .
A New Way To Detect Parkinsonsby Smell
Discovery of odorous markers for neurodegenerative disease
Scent has been used as a diagnostic tool by physicians for thousands of years. But smell tests are not common in modern medicinewhens the last time you were smelled by your doctor or received a batch of smell results back from the lab? Now, new research suggests that odors can be used to screen for Parkinsons disease, which currently is without a definitive diagnostic.
In the animal kingdom, scents emitted from a body often signal information about an individuals mental or physical state. For example, stressed rodents have been shown to excrete distinctive odors. Human body odors also have this function, emitting a wide array of odor and non-odor related chemicals called volatile organic compounds. These compounds are emitted from different areas of the human body and vary with age, diet, sex and possibly genetic background. Moreover, disease processes can influence our daily odor by changing these compounds.
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Upsit Sensitivity And Specificity
UPSIT sensitivity was 79.7% with a specificity of 68.5% using a cut-off score 25 . The overall accuracy of the diagnosis of PD was 75.3%. The ROC curve is presented as Figure 2 . Since age and gender were significant determinants of the UPSIT total score for both groups, we divided subjects into women more than 67 years old and women with an age of 67 or less. In this case, UPSIT sensitivity for PD detection was 85.7% with a 62.6% specificity for a cutoff score 25 . PD probability related to the UPSIT total score is presented as Figure 3 .
Figure 2
Can A Dog Detect Parkinsons
A related news story is about the existence of programs which train dogs, well known to have much better senses of smell than humans, to smell PD. One such program, the first of its kind established in the US, is PADs for Parkinsons and operates in the Pacific Northwest. This program was established directly as a result of Joy Milnes story. The founders of the program hypothesized that if a human can detect PD, then dogs could almost certainly be trained to do so. A program called Medical Detection Dogs based in the United Kingdom trains dogs to detect odors of a number of diseases and is working with the research program at the University of Manchester described above. Other endeavors to train dogs to detect the odor of PD exist as well.
Accounts from PADs for Parkinsons and Medical Detection Dogs certainly support the idea that dogs can be trained to identify an odor in people who have been diagnosed with PD. For both these programs, the ultimate objective is not for trained dogs to diagnose PD by smelling bio-samples, but rather to identify the chemicals that the dogs are detecting so that an early diagnostic test can be developed.
Another related issue is whether dogs can distinguish PD from other neurological conditions. Currently, this can be a clinical conundrum and it is unclear if odor detection would be helpful here.
More research is necessary but its exciting and interesting to think that in the future, the odor of PD may turn into a biomarker for PD!
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Scientists Sniff Out Parkinson’s Disease Smell
Scientists are close to establishing what causes a smell associated with sufferers of Parkinson’s disease.
They hope it could lead to the first diagnostic test for the disease.
A team from Manchester has found distinctive molecules that seem to be concentrated on the skin of Parkinson’s patients.
One in 500 people in the UK has Parkinson’s – that is 127,000 across Britain.
Losing Sense Of Smell
Most people do not connect losing their sense of smell to a Parkinson’s diagnosis. After developing motor symptoms and talking to a doctor, however, they may recall that years or even decades earlier their ability to smell decreased. This condition is called hyposmia and can impact quality of life affecting taste and, in some cases, leading to weight loss.
Parkinson’s and other neurological conditions, such as Alzheimer’s, can cause smell loss. But there are many other causes, too:
- Upper respiratory infection, such as the common cold
- Nasal problems, such as seasonal allergies or chronic sinus disease
- Head injury, if it damages the olfactory nerve or brains smell-processing centers
- Cigarette smoking
- Aging
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What More Research Needs To Be Done
The scientists subsequently teamed up with researchers in Austria who study people with REM sleep disorders in an effort to discover whether the test can spot Parkinsons before doctors can. The Guardian reports that a separate study found people with a specific kind of such disorder have a 50% risk of developing Parkinsons in later life.
If we can detect the disease early on, that would be very good news, commented Barran. It would mean we have a test that picks it up before motor symptoms appear.
In parallel, more than 1,000 Parkinsons patients and hundreds of healthy people are having their sebum analysed in order to assess how reliable the test is. Scientists will also look at whether changes in the odour reflect the progression of the disease, or even different forms of Parkinsons.
Speaking to coincide with the publication of the Manchester University findings in ACS Central Science, Professor David Dexter, deputy director of Research at Parkinsons UK, said: More research is needed to find out at what stage a skin test could detect Parkinsons, or whether it is also occurs in other Parkinsons related disorders, but the results so far hold real potential.
Both to change the way we diagnose the condition and it may even help in the development of new and better treatments for the 145,000 people living with Parkinsons in the UK.
Progress Towards A Skin Swab Test
These early findings were exciting and encouraging. The scientists knew that if they were able to identify a unique chemical signature in the skin linked to Parkinsons, they may eventually be able to diagnose the condition from simple skin swabs.
There is currently no definitive test for Parkinsons disease, with diagnosis based on a patients symptoms and medical history, a process that can take several years. The development of a test like this would therefore be a game-changer for the Parkinsons community.
With Joys help, the research team, now led by Perdita at the University of Manchester, continued to make progress. In 2019, they announced a major breakthrough the discovery of chemicals enriched in skin swabs from people with Parkinsons.
This key discovery led to further research to profile the complex chemical signature in sebum of people with Parkinsons. Through this work, scientists found subtle but fundamental changes as the condition progressed.
This meant that a skin swab could potentially not only be used to diagnose Parkinsons, but could also be used to monitor the development of the condition.
Professor Perdita Barran said: We believe that our results are an extremely encouraging step towards tests that could be used to help diagnose and monitor Parkinsons. Not only is the test quick, simple and painless but it should also be extremely cost-effective because it uses existing technology that is already widely available.
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Role Of Taste Receptors In The Pd Pathological Process
In the last few years some authors have focused their studies on specific taste performances in PD, identifying an increase in the frequency of the non-tasters for bitterness compared to healthy controls . The ability to perceive the bitter taste has gained considerable attention because of its genetic substrate. In the family of receptors for bitter, TAS2R38, a member of the T2R receptors, has been extensively studied, since the allelic diversity of the gene is able to explain much of the individual variability in the perception of the bitter taste. In fact, polymorphisms of the gene give rise to variants of the receptor with different affinity for the stimulus. T2R bitter taste receptors are G-protein coupled receptors originally identified on the tongue. Human nasal and bronchial airways express multiple T2Rs isoforms . These T2Rs recognize bacterial products and, when activated, stimulate a signaling cascade involving calcium-driven nitric oxide production increasing ciliary beating as well as directly killing bacteria .
Future studies will have to indicate whether the altered T2R observed in PD may play a specific role in the inflammatory mechanisms associated with the initiation of misfolding of α-synuclein cascade possibly by modulating the innate immunity via TLR/T2R signaling.
Why A Smell Test Is Performed
Loss of smell is one of the most common and best characterized non-motor symptoms of Parkinsons disease. Studies suggest that patients may lose their sense of smell up to 10 years before other symptoms appear.
Smell function studies showed that about 96 percent of newly diagnosed Parkinsons disease patients have lost some ability to smell. Recent studies also suggest that this could be used to identify at-risk patients earlier. Moreover, testing for loss of smell is inexpensive and easy, making it an attractive option for the diagnosis of Parkinsons.
Smell tests may also serve as a differential diagnostic tool to distinguish between Parkinsons disease and other conditions such as progressive supranuclear palsy, corticobasal degeneration, essential tremor, atypical parkinsonian syndromes, drug-induced parkinsonism, and vascular or other causes of parkinsonism.
In addition, smell tests could be used to predict whether a first-degree relative of someone with Parkinsons disease may also develop the condition in the future.
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A Rapid Diagnostic For Parkinsons
To take the smell test, the capsules are crushed between the fingers and the tape strip is peeled. This releases an aroma, and researchers can then score a persons ability to recognise the smell.
In a study, published in the Journal of the Royal Society Interface, a small group of eight people with Parkinsons disease took the capsule smell test, as well as a scratch and sniff smell test. In both tests, they were asked to identify six different scents: coconut, menthol, cherry, orange, clove and onion. In each round, patients were asked to share what they smelled.
The results showed that odours were easier to identify in the capsule smell test. The participants also highlighted the ease of crushing capsules compared to the scratching method, particularly for those with tremors. Although smell tests for diagnosis already exist, they are expensive and not widely available.
Dr Ahmed Ismail, lead researcher of the study, said: Our capsule-based smell test can assist in the rapid diagnostic of various diseases linked to the loss of smell.
Dr Ahmed Ismail, lead researcher of the study.
He continued: Most of the smell tests on the market depend on using paperboard items treated with a fragrant coating called scratch and sniff, in which you need to scratch a card to release the odour. The problem with this approach is that the amount of odour released depends on the extent to which the individual scratches, something that might affect the outcome of the test.
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Smell Of Parkinsons Finally Identified Early Detection Test On The Way
In the early 1980s, nurse Joy Milne began to notice a distinct musky odor on her husband. A few years later her husband was diagnosed with Parkinson’s disease, but Milne didn’t connect the two disparate events until she later joined a Parkinson’s charity and started meeting other sufferers. It was here she began to notice every person with Parkinson’s disease could be identified by this same unusual and distinct odor.
In 2012, Milne approached a neuroscientist giving a talk on Parkinson’s and claimed to be able to smell the disease. The scientist decided to test her claim. Six Parkinson’s patients, and six healthy subjects wore clean t-shirts for a single day, and the 12 t-shirts were then individually bagged and presented to Milne. After extensive sniff testing, Milne ultimately guessed 11 out of 12 correctly, only misidentifying one t-shirt as being worn by a Parkinson’s patient, when in fact it was a healthy subject.
Since then, a team of scientists has been working to isolate and identify the compounds Milne associated with Parkinson’s. Now, after several years of work, the researchers claim they’ve been successful and suggest the discovery could lead to an early detection test for the devastating disease.
The new research was published in the journal ACS Central Science.
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