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Defining discordance in twin studies of risk and protective factors for late life disorders

Published online by Cambridge University Press:  21 February 2012

Margaret Gatz ,
Nancy L Pedersen ,
Michael Crowe  and
Amy Fiske
Margaret Gatz*
Affiliation:
Department of Psychology, University of Southern California, Los Angeles, California, USA; Department of Medical Epidemiology, Karolinska Institutet, Stockholm, Swedengatz@rcf.usc.edu
Nancy L Pedersen
Affiliation:
Department of Medical Epidemiology, Karolinska Institutet, Stockholm, Sweden; Department of Psychology, University of Southern California, Los Angeles, California, USA
Michael Crowe
Affiliation:
Department of Psychology, University of Southern California, Los Angeles, California, USA
Amy Fiske
Affiliation:
Department of Psychology, University of Southern California, Los Angeles, California, USA
*
*Correspondence: Dr Margaret Gatz, Department of Psychology, University of Southern California, 3620 McClintock, Los Angeles, California90089-1061, USA. Tel: 213 740 2212; Fax: 213 746 5994

Abstract

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In studies that employ matched pair analysis to identify environmental exposures important for a disorder, criteria for discordant pairs are seldom discussed. Yet several assumptions concerning the definition of discordancy may have considerable influence over what results are found. Problems are exacerbated when age of onset for a disorder is late in life. We propose a new set of criteria for defining discordant pairs in studies of dementia, taking into account duration of discordance and competing causes of mortality, and evaluate the consequences of choosing alternative definitions of discordancy. Twin Research (2000) 3, 159–164.

Keywords

co-twin controlAlzheimer's diseasedementiagenetic epidemiology
Type
Articles
Information
Twin Research and Human Genetics , Volume 3 , Issue 3 , 01 June 2000 , pp. 159 - 164
Copyright
Copyright © Cambridge University Press 2000