2023 American Academy of Neurology Abstract Website

Objective:

We quantified the conversion rate from essential tremor (ET) to ET with Parkinson's disease (ETPD) in a prospective, longitudinal cohort study of ET cases. We compared the observed rate to that reported in the epidemiological literature.

Background:

There has been a longstanding dialogue as to whether ET increases the risk of developing PD. While there are relevant cross-sectional data, there are almost no longitudinal, prospective data.

Design/Methods:

We enrolled ET cases in a prospective, longitudinal study. A senior movement disorders neurologist evaluated standardized neurological examinations every 18 months.

Results:

193 ET cases (mean age = 78.1 ± 9.6 years, range = 55 – 96) had a mean follow-up duration of 4.1 years. Seven (3.6%) converted from ET to ETPD. The incidence of PD among ET cases was 7/792.9 person years [py] (i.e., 882.8/100,000 py). A meta-analysis of the incidence (per 100,000 py) of PD in 14 studies from 13 countries across 4 continents reported an incidence of PD = 61.21 (males, >40 years) and 37.55 (females, >40 years). The incidence/100,000 py in males peaked in the 80 – 89 year old age group (258.47) and in females in the 80 – 89 year old age group (103.48 py). The above published values are 3.4 - 23.5 times lower than the value we observed for ET.

Conclusions:

The incidence of PD in an ET cohort is substantially higher than that reported in historical, population-based control groups across numerous countries. Additional prospective, longitudinal data are needed to further explore this association.