Shedding tears could help tell if you have Parkinson’s disease, a new study found.
Biomarkers could be simply detected in tears enabling doctors to diagnose the neurological illness that affects one in 500 people.
Scientists found there were minute differences in the levels of a particular protein shed in tears.
The test could help detect the disease years before symptoms develop allowing doctors to prescribe treatments such as drugs to restore dopamine in the brain.
Researchers found differences in the levels of a particular protein, alpha-synuclein, in the tears of people with Parkinson’s compared to controls
The disease, which affects 127,000 Britons and 600,000 Americans, is incurable and causes involuntary shaking of particular parts of the body, slow movement and stiff and inflexible muscles.
Professor of neurology Dr Mark Lew said: ‘We believe our research is the first to show that tears may be a reliable, inexpensive and noninvasive biological marker of Parkinson’s disease.’
He explained tears contain various proteins produced by the secretory cells of the tear gland, which is stimulated by nerves to secrete these proteins into tears.
Because Parkinson’s can affect nerve function outside of the brain, researchers hypothesised any change in nerve function may be seen in the protein levels in tears.
The study involved taking tear samples from 55 people with Parkinson’s and comparing theses to tear samples from 27 people without Parkinson’s but who were the same age and gender.
The researchers from the Keck School of Medicine of the University of Southern California in Los Angeles analysed the tear samples for the levels of four proteins.
Researchers found differences in the levels of a particular protein, alpha-synuclein, in the tears of people with Parkinson’s compared to controls.
Additionally, levels of another form of alpha-synuclein, oligomeric alpha-synuclein, which is alpha-synuclein that has formed aggregates that are implicated in nerve damage in Parkinson’s, were also significantly different compared to controls.
They suggested it is also possible the tear gland secretory cells themselves produce these different forms of alpha-synuclein that can be directly secreted into tears.
Total levels of alpha-synuclein were decreased in people with Parkinson’s, with an average of 423 picograms of that protein per milligram (pg/mg) compared to 704 pg/mg in people without Parkinson’s.
But levels of oligomeric alpha-synuclein were increased in people with Parkinson’s, with an average of 1.45 nanograms per milligram of tear protein (ng/mg) compared to 0.27 ng/mg in people without the disease.
A picogram is 1,000 times smaller than a nanogram.
Professor Lew concluded: ‘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 noninvasive manner is exciting.
‘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.’
Further studies are planned in larger groups to investigate whether these protein changes can be detected in tears in the earliest stages of the disease, before symptoms start.
The findings of the preliminary study was presented at the American Academy of Neurology’s 70th Annual Meeting in Los Angeles.