Hostname: page-component-cd9895bd7-dzt6s Total loading time: 0 Render date: 2024-12-25T14:29:22.709Z Has data issue: false hasContentIssue false

Can Comparison of MZ- and DZ-Twin Concordance Rates be Used Invariably to Estimate Heritability?

Published online by Cambridge University Press:  21 February 2012

Peter V. Tishler*
Affiliation:
Genetics Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts United States of America; Channing Laboratory,Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America. [email protected]
Vincent J. Carey
Affiliation:
Channing Laboratory,Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America.
*
*Address for correspondence: Peter V. Tishler, M. D., Channing Laboratory, 181 Longwood Avenue, Boston, Massachusetts 02115, United States of America.

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Proponents of the validity of the classical MZ-DZ twin comparison model for calculating heritability claim that the environments influencing MZ and DZ twin individuals are essentially identical. This ‘equal environments assumption’ may or may not be universally true when applied to the analysis of subjective traits. We examined the validity of this assumption as applied to the propensity for smoking cigarettes, reasoning that equality of environments should lead to equal smoking prevalences in MZ and DZ twin individuals. We identified 8 twin populations with data on smoking. We compiled odds ratios (ORs) for ever smoking in MZ and DZ twin individuals in these 8 studies and overall, using a fixed-effects meta-analytic method based on the Mantel-Haenszel procedure. The prevalence of smoking was less in MZ twin individuals than in DZ twin individuals in 7 of 8 studies. The overall OR was 0.86 (95% confidence interval 0.84, 0.89). ORs were virtually unchanged when the analyses were stratified for gender and age, and no differences were found in relation to the location of the study, the date of the study or the birth years of the cohorts. For cigarette smoking, the environments of MZ and DZ twins may not be co-equal. For subjective traits, heritability estimates may be influenced by these unequal environmental factors that differentially affect their development and characteristics in MZ and DZ twins.

Type
Articles
Copyright
Copyright © Cambridge University Press 2007