(CBS/AP) What causes Parkinson's disease? New research links the incurable brain ailment to five genes, bolstering evidence that Parkinson's is largely a matter of heredity.
The discovery doesn't mean there are new treatments just yet, but experts are optimistic they are getting closer. Current treatments are limited.
"The major common genetic variants for Parkinson's have been found," said Nick Wood, a professor at the Institute of Neurology at University College London, one of the researchers who led the study. "We haven't put together all the pieces of the puzzle yet, but we're not that far off," he said. He predicted a diagnostic test might be ready within a few years.
Until recently, scientists hadn't been sure what caused Parkinson's disease, but assumed environmental factors such as exposure to chemicals or past head injuries were largely to blame.
Scientists analyzed genetic samples from more than 12,000 people with Parkinson's and more than 21,000 from the general population in Europe and the U.S. They found people with the highest number of mutations in 11 genes linked to Parkinson's - the five newly identified genes and six that were previously identified - were 2.5 times more likely to develop the disease than people who had the smallest number of mutations.
The average person has a 2.5 percent chance of developing Parkinson's disease. The risk for people whose close relatives have the illness is about six percent.
Parkinson's strikes when brain cells don't make enough of the chemical dopamine. That leads to symptoms including tremors, rigidity and slowness of movement. It mostly affects people over 50, though younger people, including actor Michael J. Fox, sometimes develop the disease.
The study was published online Wednesday in the medical journal "Lancet."