The biggest genetic indicator of Parkinson's disease is 10 times more prevalent in Ashkenazi Jews than in the general population, research has revealed.
A global study will now track how often the mutated LRRK2 gene - which is present in 10 per cent of Ashkenazim - develops into the disease.
The British arm of the investigation into the gene is being led by the National Institute of Health Research. Gemma Loebenberg, a specialist at the NIHR, said a second mutated gene known as GBA was also more common in Jews.
"People who have one of those genes have a 50 per cent chance of passing the mutation on to their children," she said.
A saliva test can be used to show whether a patient has the mutated genes.
Volunteers are then given free genetic counselling to discuss their results, with those who have either gene being offered the chance to have tests for Parkinson's at regular intervals.
Ms Loebenberg, who is Jewish, said: "Just doing the saliva test lets us see if it's the same rate in the UK Ashkenazi population as worldwide."
She called on community members who have Parkinson's, or who have relatives with the disease, to volunteer for the study, which is being run at 32 clinical sites worldwide.
Speaking ahead of Parkinson's Awareness Week, which begins on Monday, Ms Loebenberg said: "Obviously there will be people who have concerns about whether they have one of the genes, but it's important in improving our current understanding of Parkinson's, and for improving future treatment options.
"Even if it doesn't benefit you, it could benefit your neighbour, your children or your friends in the future.
"We're researching these genes to improve our understanding of why some people develop Parkinson's and some don't. The idea is to track development before the severe symptoms set in, and in the long-term, this will contribute to finding a cure."
The NIHR study, under the Parkinson's Progression Markers Initiative, is sponsored by the Michael J Fox Foundation.
Contact gemma.loebenberg@nihr.ac.uk if you would like to volunteer, or go to https://www.michaeljfox.org/page.html?ppmi-genetics for more information.
