Smelling Parkinson’s disease

Joy Milney, a 72-year-old woman living in Scotland is “hypersomic,” meaning she has an unusually sensitive nose. When she met her future husband, she loved the way he smelled: salt and musk with a touch of leather. When he was still in his thirties, she found that his odor had changed, along with his personality. After about ten years, Joy began to think the changes might be symptoms of some disease. He was eventually diagnosed as having Parkinson’s disease—a rather early onset.

Joy talked her husband into attending a meeting of local Parkinson’s patients and their caregivers. There, she discovered that all the other Parkinson’s patients in the room smelled like her husband. A lightbulb went off and she managed, after many months, to locate a scientist who would arrange some tests. For the test they arranged for six Parkinson’s patients and six healthy controls to wear fresh T-shirts for 24 hours. Afterward, Joy smelled the T-shirts at random and correctly identified the Parkinson’s people. (She made one false positive identification from a non-Parkinson’s patient who later turned out to have an undiagnosed case.)

Long story short: it turns out that it was not sweat but sebum that was causing the smell. Sebum is a substance secreted by the skin—a sort of waste disposal for our bodies. Scientists fed samples of sebum into a gas chromatograph-mass spectrometer that separated the substance into its component molecular parts. A few of these chemicals were found to be in higher concentrations in the sebum of Parkinson’s patients. Apparently, these chemicals were causing disruptions in two important metabolic pathways that are particularly active in our brains. The byproducts of these chemicals were being transported to the sebum.

Because of this research, people are now imagining the possibility of using sebum tests to screen for Parkinson’s on a broad scale, with the idea of identifying the disease before symptoms become obvious. Amazon has been in touch with the researchers about the possibility of adding a smell functionality to its Alexa devices. It’s sort of laughable imagining what Alexa might say to you as you walk by.

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