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Neurology. 2004 Jan 27;62(2):208-11.

High concordance for essential tremor in monozygotic twins of old age.

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  • 1Department of Neurology, Christian-Albrechts-University Kiel, Germany.

Abstract

OBJECTIVE:

To assess the relative contribution of genetic and environmental factors for the etiology of essential tremor (ET) and to explore the effect of different diagnostic criteria.

METHODS:

A total of 2,448 twins of the Danish twin registry aged 70 years or more were screened for ET by an interview and an Archimedes spiral test. All twin pairs (n = 162) with a positive screening test of at least one of the twins were recontacted and 218 individuals (109 pairs) were interviewed and examined by a movement disorder specialist. The consensus criteria of the Tremor Investigation Group were applied to diagnose ET.

RESULTS:

Twenty-nine twins fulfilled the criteria of definite, 7 of probable, and 56 of possible ET. The probandwise concordance rate for the broadest definition of ET was 77% for monozygotic twins (MZ) and 59% for dizygotic twins (DZ). However, in an analysis restricted to cases of probable and definite ET, the concordance rates were 93% and 29%. The heritability for the liability to ET ranged from 93% to 99% using a general population prevalence of 1.2% for white 70+-year-olds. The inclusion of probable and exclusion of possible cases in the diagnosis of ET produced the highest concordance rates.

CONCLUSION:

The high concordance among MZ twins of very old age in this first population-based twin study of ET suggests that a disease phenotype consisting of definite and probable ET has a high heritability and hence is a good candidate for a phenotype to be used in linkage studies.

PMID:
14745055
[PubMed - indexed for MEDLINE]
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