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Neuroepidemiology. 2018;50(1-2):41-46. doi: 10.1159/000486485. Epub 2018 Jan 16.

Comparative Burden of Subclinical Tremor in a Cohort of Normal Individuals Stratified by Familial Risk for Essential Tremor.

Author information

1
Department of Neurology, Yale School of Medicine, Yale University, New Haven, Connecticut, USA.
2
Department of Chronic Disease Epidemiology, Yale School of Public Health, Yale University, New Haven, Connecticut, USA.
3
Center for Neuroepidemiology and Clinical Neurological Research, Yale School of Medicine, Yale University, New Haven, Connecticut, USA.
4
Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York, USA.

Abstract

BACKGROUND:

The burden of mild (i.e., subclinical) tremor within essential tremor (ET) families is not fully understood. We assessed the burden of mild tremor in a cohort of 287 adults, none of whom reported tremor or were diagnosed with ET.

METHODS:

We recruited adults in 2 groups based on the familial risk for ET: 244 high-risk individuals (i.e., reporting one or more first-degree relative with ET) and 43 low-risk individuals (i.e., reporting no relatives with ET). Tremor was objectively assessed on 4 hand-drawn spirals (total spiral score = 0-12). Mild tremor was defined using 3 different cut points.

RESULTS:

The prevalence rates of mild tremor among high-risk individuals ranged from 41.4 to 98.4% and were highly dependent on the cut point. Above a certain threshold (i.e., a total spiral score ≥5), 1-in-5 (i.e., 19.7%) high-risk individuals exhibited mild tremor, whereas no low-risk individuals did. High-risk individuals were 3.09-4.50 times more likely than low-risk individuals to exhibit mild tremor.

CONCLUSION:

The burden of ET extends beyond the boundaries of the clinically defined disease, and partially expressed forms of ET are abundant in ET families. This fact greatly complicates gene-finding studies and epidemiological studies whose goal is to detect disease-linked associations.

KEYWORDS:

Epidemiology; Essential tremor; Genetics; Penetrance; Risk; Subclinical

PMID:
29339654
PMCID:
PMC5860954
[Available on 2019-01-16]
DOI:
10.1159/000486485

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