Several smaller studies have suggested the genetic link between the two conditions, "but there have always been questions based on their size and controls," Sidransky said. "Once and for all, we have put together a large enough number so that no one will question the results."
The study she led involved 16 institutions around the world. A listing of the institutions and researchers filled a complete page on the journal in fine print.
Those researchers examined the frequency of GBA variants in 5,691 people with Parkinson's disease, including 780 Ashkenazi Jews, an ethnic group in which Gaucher disease is more common. Their data was matched with genetic information from 4,898 disease-free individuals, including 387 Ashkenazi Jews.
At least one of two common GBA variants was found in 3.2 percent of the people with Parkinson's disease, but only 0.6 percent of the disease-free individuals. Among the Ashkenazi participants, 15.3 percent of those with Parkinson's disease carried a GBA variant, compared to 3.4 percent of disease-free Ashkenazi individuals.
In addition to increasing the risk of Parkinson's disease, presence of a GBA variant was associated with early onset of the condition, four to five years sooner than ordinarily seen, the study found.
"Its importance is that it may indicate a new pathway to explore for the etiology [cause] of Parkinson's disease, and ultimately a target for drug discovery," said Dr. Karen Marder, a professor of neurology at Columbia University Medical Center, and one of the researchers in the trial.
The discovery raises some possible issues about genetic counseling, Marder said, but more work must be done before that can influence medical practice.
"This is among the most important susceptibility factors for Parkinson's that has ever been discovered, but it is premature to talk about using it in clinical practice," she said.
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