When you think of Parkinson’s disease, tremors, slow movement and balance problems probably come quickly to mind. But other signs of this neurologic disease can appear years, or even decades, before the motor symptoms become obvious.

Recognizing these early signs would allow diagnosis and treatment to begin sooner so that the course of the disease could be slowed down. However, the first signs of Parkinson’s to emerge—such as sleep disturbances, depression and constipation—are so common that they’re not easily identified as Parkinson’s symptoms.

Exciting development: Researchers may have now identified a new biomarker for Parkinson’s that could be used as a reliable, noninvasive and inexpensive way to diagnose the disease much earlier than was previously possible.

Background: In prior studies, scientists have found biomarkers for Alzheimer’s disease and multiple sclerosis in tears, so researchers from the Keck School of Medicine of the University of Southern California in Los Angeles hypothesized that biomarkers for Parkinson’s might be present in tears as well. Preliminary studies had been done with saliva, but concentrations of the necessary proteins were too low to be helpful.

New study: Researchers collected tears from 55 people in various stages of Parkinson’s disease and 27 people without Parkinson’s who were the same age and gender. They then measured the levels of four specific proteins found within the tears.

Results: Levels of two tested proteins were the same for people with and without Parkinson’s, but the tears of people with Parkinson’s contained significantly less alpha synuclein than the tears of healthy participants. They also contained significantly more oligomeric alpha-synuclein, a related protein implicated in the nerve damage associated with Parkinson’s.

Bottom line: More research is needed with larger groups of people, but researchers are hopeful that something as simple as tears could help neurologists to easily determine who has Parkinson’s in the beginning phases of the disease so that treatment can be started early.

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