June 2 (UPI) -- The effects of deep brain stimulation continue to be effective in people with Parkinson's disease 15 years after the device is implanted, according to a study published Wednesday in the journal Neurology.
Researchers found that study participants experienced significant improvement in motor symptoms, as well as a reduction in medications, 15 years after receiving the implant.
Parkinson's disease can progressively affect speech, walking, and balance due to a gradual reduction of dopamine in the brain.
The disease results in muscle stiffness, tremor and slowness of movement, which can be treated with a medication called levodopa that temporarily restores dopamine.
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The process of rising and falling levels of dopamine can cause dyskinesia, a side effect that results in twisting, swaying or head bobbing.
Deep brain stimulation controls motor symptoms from Parkinson's disease with electrodes that are placed in certain areas of the brain. They're connected to a device placed in the upper chest which controls electrical impulses.
"Deep brain stimulation benefits seem to last for years but not enough data have been available to show these effects are still present more than 15 years after surgery," study co-author Dr. Elena Moro said in a press release.
"It is exciting to report that our study found in the long run, deep brain stimulation continues to be effective," said Moro, a neurologist and professor at the Grenoble Alps University in France.
For the new study, researchers identified 51 people who had deep brain stimulation devices implanted at the hospital at Grenoble Alpes.
The average age for diagnosis of the disease was 40, but the average age for device implementation was 51. Study participants had the device for an average of 17 years.
Researchers found that, when comparing data on before and after implantation of the devices, the number of times participants experienced dyskinesia was reduced by 75%.
Researchers also found that the amount of time spent in an "off state" -- when medication was no longer working well -- was reduced by 59%. The use of medications to control dopamine was also reduced by 51%.
Additionally, there were only a few side effects from using the stimulation, and those side effects were manageable, according to the researchers.
"Our study also found that despite the natural progression of Parkinson's disease and the worsening of some symptoms that become resistant to medications over the years, participants still maintained an overall improvement in quality of life," Moro said.
"Future studies should continue to examine the benefits of deep brain stimulation over longer periods of time and in larger groups of people," Moro said.
