Parkinson’s and Essential Tremor Share ‘Central Origin,’ Study Suggests

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by Vanda Pinto, PhD |

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Accidental falls and co-existing conditions, or comorbidities, like fatigue, depression, and sleeping problems are frequent in older adults with either Parkinson’s disease or essential tremor syndrome, suggesting “similar central origins” for these two disorders, a study reported.

Its data also support essential tremor being found in older Parkinson’s patients, and Parkinson’s in those with essential tremor.

“These shared characteristics may explain why many patients often have a diagnosis of both [essential tremor] and [Parkinson’s disease] within 2 years of their [diagnosis] date,” the study’s scientists with Cala Health — a company that develops devices to treat hand tremors, and markets the Cala Trio device for essential tremor — wrote.

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Study findings were presented at the ISPOR 2022 conference, held May 15-18 in Washington, D.C., and virtually, in the abstract “Co-Morbidities and Mechanistic Similarities of Essential Tremor and Parkinson’s Disease and Resulting Diagnostic Challenges.”

Parkinson’s disease and essential tremor share symptoms such as shaking, or tremors, caused by involuntary muscle contractions. However, essential tremor is a more common and generally less severe movement disorder.

Tremors are thought to be triggered by abnormal brain waves from specific areas responsible for controlling body movements. Since treatment with deep brain stimulation (DBS), a surgery to place electrodes in the brain that stimulate key regions, has shown effectiveness in both Parkinson’s and essential tremor, researchers have wondered if the two have a similar cause.

A pair of scientists at Cala Health looked at comorbidities and other issues present in these two groups of patients by analyzing health claims in a large commercial and Medicare database (Truven Health Analytics) between 2013 and 2019.

Data covering 18,193 Parkinson’s patients, 13,559 people with essential tremor, and a control group of 633,066 adults without either condition were included in the analysis. All involved were older than age 40.

Within the first two years after a diagnosis, those ages 65 or older with Parkinson’s or essential tremor had a higher prevalence of similar comorbidities and problems like falls compared with controls, results showed.

Areas of overlap between the patient groups included accidental falls (24.5% among Parkinson’s patients, 14.1% among those with essential tremor, and 2% among controls), bradykinesia or slowness of movement (10.0% vs. 14.9% vs. 0.3%), depression (25.1% vs. 22.4% vs. 14.4%), fatigue (35.7% vs. 28.1% vs. 17.4%), and sleep disorders (30.5% vs. 30.3% vs. 14.3%).

Diagnostic claims filed by patients with pharmacy and medical records spanning at least one year prior to a diagnosis and two years after it also indicated an overlap in the two conditions. Among these people, “only 10.7%” of those with essential tremor did not have a diagnosis claim at any point for Parkinson’s disease, and 20.4% of Parkinson’s patients did not have a similar claim at any point for essential tremor, the researchers wrote.

“These findings suggest that [essential tremor] and Parkinson’s disease action tremor may have similar central origins,” Dhira Khosla, medical director at Cala Health and a study co-researcher, said in a press release.

Cala Trio, a device worn on the wrist, is cleared by the U.S. Food and Drug Administration (FDA) to ease action tremors in the hands due to essential tremor. It works by sending electrical signals to stimulate tremor-associated nerve cells in the wrist and help relieve hand tremors.

It also was given breakthrough device status by the FDA as a potential wrist-worn treatment of action tremors for those with Parkinson’s. This status works to speed the development of medical devices with the potential to more effectively treat serious conditions, and the company said it plans to submit this study’s findings for FDA review.

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