Therapies, Research Funding, and Racial Diversity in Essential Tremor: A Systematic Review of the Literature

Essential tremor (ET) is one of the most common tremor disorders in the world. Despite this, only one medication, propranolol, is approved by the Food and Drug Administration to treat it.

We analyzed controlled clinical trials in ET, spanning the last 50 years, to identify potential shortcomings in the therapeutic clinical pipeline.

Outcomes reviewed included demographics (specifically gender and race), therapeutic modalities, funding information, location of research, and trends over time. Clinical trials published in English were identified in scientific databases (Pubmed, SCOPUS, Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry Platform from 1970 through December 2021. Included trials were prospective, either single- or double-blinded (including blinded video assessments for surgical trials), with change in limb, head, or voice tremor as the primary outcome measure.

One hundred and eighty-six controlled clinical trials were accepted for extraction, including 4207 patients. Of the 145 trials that included gender, males comprised 59% of the patient population. Only 6.4% of studies provided racial demographics; in these studies, 70.5% of patients were Caucasian. The most common therapeutic modality over the past 50 years was "pharmaceutical" (56%), and the most common pharmaceutical studied was propranolol (32%). 41% of clinical trials reported no specific funding.

Future efforts should focus on increasing funding for clinical trial research in ET worldwide, and trials should be designed to be more inclusive of disadvantaged minorities.