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Elan D. Louis, MD, MS; Livia F. Barnes, MPH; Blair Ford, MD; Seth L. Pullman, MD; Qiping Yu, PhD

Arch Neurol. 2000;57:723-727.

Background  Ethnic differences in the clinical characteristics (severity and distribution) of essential tremor (ET) have not been studied. The presence of these differences suggests that ET is not a homogeneous disease and that there is variability in disease expression under different circumstances. As part of a community-based study, we evaluated a multiethnic group of cases.

Objective  To assess whether there are ethnic differences in the clinical characteristics of ET.

Methods  Elderly residents of Washington Heights–Inwood, New York, were enrolled in a community-based health study (N=2117). Participants underwent a medical interview and a neurological examination conducted by a neurologist, and subjects with ET were identified. These subjects with ET were then enrolled in a community-based study of ET and underwent a tremor interview, a videotaped tremor examination, and in some cases, a performance-based test of function and quantitative computerized tremor analysis. A total tremor score (range, 0-36, with 0 indicating no tremor and 36 indicating maximum tremor) was assigned to each subject based on 2 neurologists' ratings of the tremor examination.

Results  Among 62 subjects with ET (white [n=16], African American [n=18], and Hispanic [n=28]), there were ethnic differences in the total tremor score (F=3.68, P=.03). In a multiple regression model adjusting for age, white subjects had a mean total tremor score that was 5.3 points lower than that of nonwhite subjects (P=.008). We divided the nonwhite group into African American and Hispanic subgroups. In a regression model adjusting for age and duration, the white group had a mean total tremor score that was 6.1 points lower than that of the Hispanic group (P=.07) and 7.2 points lower than that of the African American group (P=.05). The mean performance-based test score was 1.7 times higher in the African American group and 2.1 times higher in the Hispanic group compared with the white group (P=.38). No subjects in the African American group had head tremor, while 4 subjects in the white group (25%) and 8 subjects in the Hispanic group (29%) did have head tremor (²=6.17, P=.05).

Conclusions  There are ethnic differences in the expression of ET, suggesting that ET is not a homogeneous disorder. These differences may reflect phenotypic variability caused by genotypic differences or differences in exposure to environmental factors that influence tremor.

From the Gertrude H. Sergievsky Center (Dr Louis and Ms Barnes) and the Department of Neurology (Drs Louis, Ford, Pullman, and Yu), College of Physicians and Surgeons, Columbia University, New York, NY.

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