The findings provide strong evidence that Parkinson's disease has an important genetic component and is not caused exclusively by environmental factors, said Margaret Pericak-Vance, director of Duke's Center for Human Genetics and senior author of the study that appears in the Nov. 13 issue of the Journal of the American Medical Association.
The new findings challenge the results of previously published studies of twins that suggested environmental factors are the primary cause of Parkinson's disease, with only a minor genetic contribution.
While most scientists agree there is a genetic link, the consensus has been that it is mostly in the rare, early-onset form of the disease in people diagnosed before age 40.
"Like many complex traits, it's likely that Parkinson's disease is caused by a web of interacting genetic and environmental risk factors, in which specific genetic templates are more susceptible to the influences of environmental exposures. Further studies to identify the molecular pathways affected by the responsible genes will provide invaluable insight into the complex etiology and potential treatment of Parkinson's disease," Pericak-Vance said.
The study was funded by grants from the National Institutes of Health and by GlaxoSmithKline.
The Duke researchers led a team from 16 institutions across the United States and Australia searching for families with one or more members with Parkinson's disease. The researchers identified 174 families and collected blood samples from as many members as possible to conduct genetic analyses to spot any common genetic factors that might confer susceptibility to Parkinson's.
Parkinson's disease, a disorder of the nervous system that causes tremors and muscular rigidity, affects more than 1 million people in the United States.
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