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No Evidence of Sex Differences in Heritability of Irritable Bowel Syndrome in Swedish Twins

Published online by Cambridge University Press:  21 February 2012

Pia Svedberg*
Affiliation:
Section of Personal Injury Prevention, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden. Pia.Svedberg@ki.se
Saga Johansson
Affiliation:
Department of Epidemiology, AstraZeneca R&D Mölndal, Mölndal, Sweden; Institute of Medicine, Sahlgrenska Academy, Göteborg University, Göteborg, Sweden.
Mari-Ann Wallander
Affiliation:
Department of Epidemiology, AstraZeneca R&D Mölndal, Mölndal, Sweden; Department of Public Health and Caring Science, Uppsala University, Uppsala, Sweden.
Nancy L. Pedersen
Affiliation:
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden; Department of Psychology, University of Southern California, Los Angeles, California, United States of America.
*
1Address for correspondence: Pia Svedberg, PhD, Section of Personal Injury Prevention, Department of Clinical Neuroscience, Karolinska Institutet, Berzeliusv.3, floor 6, SE-171 77 Stockholm, Sweden.

Abstract

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Studies have shown that familial aggregation is of importance for abdominal symptoms including irritable bowel syndrome and there are a few reports of a moderate heritability for irritable bowel syndrome. Sex differences in prevalence and incidence of irritable bowel syndrome have been demonstrated however less is known about sex differences in heritability. The objective was to investigate whether there were sex differences in heritability of irritable bowel syndrome while accounting for different prevalences among women and men in different age groups. A sample of 45,750 Swedish twins, whereof 16,961 were complete twin pairs, participated in a telephone interview. The sample was divided into three age groups (40–54, 55–64 and 65 years and older) and the diagnosis of irritable bowel syndrome was operationally defined with a number of disorder specific symptoms. Standard biometrical model fitting analyses were conducted using raw ordinal data from same-sex and opposite-sex twins. The prevalence of irritable bowel syndrome was greater among women than men and more prevalent at younger ages (e.g., women 10.3%, men 6.3% at ages 40–54 years vs. women 6.1%, men 4% at ages over 65 years). The heritability of the disorder was approximately 25% in all age groups. We found no evidence for sex differences in heritability in any of the age groups, however, models allowing prevalences of irritable bowel syndrome to differ between sexes and age groups fitted best.

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Articles
Copyright
Copyright © Cambridge University Press 2008