Parkinson's disease is a neurological disorder that causes tremors or shaking when standing, sitting or lying still. Doctors usually diagnose it by looking at your medical history, a physical and neurological examination and a review of your symptoms.
But now preliminary research suggests that your tears may reveal if you are at risk of Parkinson's disease.
Biological marker of Parkinson's
When people shed tears, certain proteins are released. Levels of those proteins are different in people with Parkinson's compared to those without the disease, according to a preliminary study.
"We believe our research is the first to show that tears may be a reliable, inexpensive and non-invasive biological marker of Parkinson's disease," said study author Dr Mark Lew, of the University of Southern California School of Medicine.
Dr Lew's team analysed tear samples from 55 people with Parkinson's and 27 people without the disease. Levels of one type of protein were higher and levels of another type of protein were lower in people with Parkinson's, the findings showed.
The proteins in tears are produced by cells in the tear gland through nerve stimulation. Because Parkinson's can affect nerve function outside of the brain, the researchers wanted to investigate if disease-related changes in nerve function could be revealed by analysing tears.
"Knowing that something as simple as tears could help neurologists differentiate between people who have Parkinson's disease and those who don't in a non-invasive manner is exciting," Dr Lew said in a news release from the American Academy of Neurology.
"And because the Parkinson's disease process can begin years or decades before symptoms appear, a biological marker like this could be useful in diagnosing, or even treating, the disease earlier," he added.
However, that's still far in the future. Further research with larger groups of people is needed to find out if tear samples could reveal Parkinson's in its earliest stages, before symptoms develop, the study authors said.
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