A new early warning signal for Parkinson’s disease which appears years before any symptoms has been uncovered by scientists.
Researchers from King’s College London found damage to the brain’s serotonin system was an “excellent marker” for the cruel long-term disease.
The second most common neurodegenerative disorder after Alzheimer’s disease affects one in 500 people, according to the NHS.
Boxing legend Muhammad Ali died from the disease, which causes a loss of dopamine in the brain leading to involuntary shaking and stiff muscles.
But the new study, published in The Lancet Neurology, found serotonin levels gave earlier detection rates than dopamine for those at greatest risk of Parkinson’s.
Study first author Heather Wilson, researcher at the Institute of Psychiatry, Psychology & Neuroscience (IoPPN), said: ‘We found that serotonin function was an excellent marker for how advanced Parkinson’s disease has become.
“Crucially, we found detectable changes to the serotonin system among patients who were not yet diagnosed.
“Therefore, brain imaging of the serotonin system could become a valuable tool to detect individuals at risk for Parkinson’s disease, monitor their progression and help with the development of new treatments.”
Previous studies have shown the incurable long-term disease takes hold in the brain a long time before patients notice symptoms.
But studying its crucial early stages when treatments could slow its process is notoriously difficult.
The study has linked Parkinson’s earliest stages with serotonin for the first time – challenging conventional literature on it – and could lead to new screening tools for identifying people at greatest risk.
The study’s Chief investigator Professor Marios Politis, Lily Safra Professor of Neurology & Neuroimaging at IoPPN, said: “Parkinson’s disease has traditionally been thought of as occurring due to damage in the dopamine system, but we show that changes to the serotonin system come first, occurring many years before patients begin to show symptoms.
“Our results suggest that early detection of changes in the serotonin system could open doors to the development of new therapies to slow, and ultimately prevent, progression of Parkinson’s disease.”
People with Parkinson’s disease have build-ups of the protein α-synuclein in the brain.
The cause is not known but is thought to be linked with environmental and genetic factors.
The researchers studied a minority of cases caused by “extremely rare” genetic mutations in the α-synuclein (SNCA) gene that nearly always mean the carrier develops Parkinson’s.
The SNCA genetic mutation was first found in villages in the northern Peloponnese in Greece and can also be found in people who migrated to nearby regions in Italy.
Over two years, the researchers identified 14 carriers and flew them from Greece and Italy to London for brain imaging and clinical assessments – seven of which had not begun to show any symptoms of Parkinson’s.
The test data was then compared with 65 patients with non-genetic Parkinson’s disease and 25 healthy volunteers.
The researchers found that the serotonin system starts to malfunction in people with Parkinson’s well before symptoms affecting movement occur, and before the first changes in the dopamine system.
They said the brain imaging was carried out using PET scans which are expensive and difficult to carry out.
They added further research on scanning techniques was needed to make them more affordable and straightforward for use as screening tools.