Research finds a set of gaseous molecules that give Parkinson’s disease patients a unique smell. This could be used to train dogs to detect the disease before symptoms appear.

Early Detection of Parkinson’s Disease by Smell May Be Possible

Early stages of Parkinson’s disease cause changes in skin secretions and skin bacteria resulting in a unique Parkinson’s disease smell.

How do dogs smell disease?

When a person gets an infection or has a metabolic disease, there can often be pronounced changes in how the person smells. Researchers are discovering that many disease states alter metabolism. They have also uncovered important roles in health and disease for the bacteria and other microbes that live on and in us, the human microbiome. These changes in metabolism or microbiota can lead to changes in volatile molecules, which are gaseous compounds that can produce odors or be detected with special laboratory equipment. Most of the volatile molecules can’t be detected by people using our sense of smell. But, dogs often can and have been trained to detect the onset of seizures, drops in blood sugar in diabetics, and the presence of cancer in samples.

Dogs can be trained to detect the smell associated with cancer. This ability likely relates to differences in metabolism between healthy cells and cancer cells. [Credit: InSitu Foundation]

Biologists have named the set of volatile organic compounds associated with an organism the “volatilome.” Changes in the volatilome can affect the odors associated with various parts of a person’s body or bodily excretions. We can smell changes that affect a person’s breath, sweat, urine, or feces. Dogs can detect odors that we cannot. They can detect specific changes in the volatilome and be trained to identify them and perform specific tasks when they detect them.

Will Parkinson’s disease be another condition detectable by dogs?

A woman discovered that she could detect a specific smell for people who, like her husband, had Parkinson’s disease. The scent was strongest in the upper back and forehead, which are areas where there are a special type of gland in the skin. Because most people cannot “smell” Parkinson’s diease, researchers in the United Kingdom called this woman a “Super Smeller.”

Working with this Super Smeller, they wanted to figure out what molecules caused this special scent. The researchers collected samples from the upper back of patients with Parkinson’s disease and healthy people. Then, they analyzed the composition of the gaseous molecules in the samples. Because there were so many molecules detected, the researchers used a computational approach to identify a subset that were significantly associated with the Parkinson’s disease patient samples and not the samples from healthy people.

The Super Smeller was then asked to smell various combinations of these molecules and tell which ones most strongly matched the odor of the Parkinson’s disease patients. Ultimately, the Super Smeller identified a mixture of 9 molecules as having a smell most like that of Parkinson’s disease patients. Several of these molecules are produced by bacteria that live on the skin, suggesting that the composition of the skin bacteria or the metabolism of skin bacteria changes in Parkinson’s disease patients.

The glands in the skin produce a waxy substance called sebum. Abnormally high production of this substance causes seborrheic dermatitis. Seborrheic dermatitis is an early symptom of Parkinson’s disease, which of occurs before movement problems. This study provides a foundation for developing an early detection screen for Parkinson’s disease, an e-sensor, or for training dogs to detect the onset of this disease well before symptoms occur.

Parkinson’s disease is caused by the death of specific nerves in the brain. Because patients who develop symptoms progress rapidly if left untreated, earlier detection before symptoms appear could delay the loss of the nerves and prolong the time before symptoms interfere with quality of life.

Highlighted Article

D. K. Trivedi, E. Sinclair, Y. Xu, D. Sarkar, C. Walton-Doyle, C. Liscio, P. Banks, J. Milne, M. Silverdale, T. Kunath, R. Goodacre, P. Barran, Discovery of Volatile Biomarkers of Parkinson’s Disease from Sebum. ACS Central Science 5, 599–606 (2019). DOI: 10.1021/acscentsci.8b00879 PubMed

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Cite as: N. R. Gough, Early Detection of Parkinson’s Disease by Smell May Be Possible. Medium (23 August 2019).