The Danish Twin Registry: An Updated Overview

Abstract

The Danish Twin Registry (DTR) was established in the 1950s, when twins born from 1870 to 1910 were ascertained, and has since been extended to include twins from birth cohorts until 2009. The DTR currently comprises of more than 175,000 twins from the 140 birth cohorts. This makes the DTR the oldest nationwide twin register and among the largest in the world. The combination of data from several surveys, including biological samples and repeated measurements on the same individuals, and data from Danish national registers provides a unique resource for a wide range of twin studies. This article provides an updated overview of the data in the DTR: First, we provide a summary of the establishment of the register, the different ascertainment methods and the twins included; then follows an overview of major surveys conducted in the DTR since 1994 and a description of the DTR biobank, including a description of the molecular data created so far; finally, a short description is given of the linkage to Danish national registers at Statistics Denmark and some recent examples of studies using the various data resources in the DTR are highlighted.

Heritability of Curve Patterns in Oral Glucose Tolerance Test

“…However, the genetic variation of the pattern was of almost the same magnitude in the youngest Class 1 and oldest Class 4, although there was more than 15 years difference in median age, indicating that age may not be the primary determinant of the total phenotypic variation. Although we used a population-based register for recruitment (Pedersen et al, 2019), the participants were twins, which could limit the generalizability of our findings to singletons. Nevertheless, several studies have found similar prevalences of type 2 diabetes and other diseases in twins and singletons (Christensen et al, 2001;Petersen et al, 2011).…”

“…The GEMINAKAR cohort was initiated in 1997 as an observational, prospective twin cohort study of 756 complete twin-pairs, aged 18-67 years, recruited from the nationwide populationbased Danish Twin Registry during 1997-2000 as previously described (Pedersen et al, 2019;Schousboe et al, 2003). To be included in the GEMINAKAR cohort, both twins in a pair had to be willing to participate.…”

Genetic Influence on the Peripheral Differentiation Signature of Vδ2+ γδ and CD4+ αβ T Cells in Adults

“…The studied cohort of ninety-five individuals (Table 1) was recruited from the 2008-2011 survey of middle-aged twins of the Danish Twin Registry [28] based on sample availability and overlaps with the cohort of the earlier study [27]. Zygosity was determined by a questionnaire on the degree of similarity between twins in a pair [29] and only twin pairs of the same sex were included.…”

“…However, we have previously reported correlations of CD4+ and CD8+ T cell differentiation indices in CMV-seropositive monozygotic (MZ) but not in dizygotic (DZ) twin pairs [27], consistent with a strong genetic influence. Here, we studied the genetic impact on the "unconventional" γδ T cell compartment in comparison to the "classical" CD4+ and CD8+ T cells in a subsample of the same cohort [27] of middle-aged MZ and DZ twin pairs from the Danish Twin Registry [28]. Significantly greater similarity between MZ twins, who share all their genes, compared to DZ twins, sharing approximately half of their genes, implies the existence of a genetic influence on the investigated trait.…”

A Genome-Wide Integrative Association Study of DNA Methylation and Gene Expression Data and Later Life Cognitive Functioning in Monozygotic Twins

“…MADT was initiated in 1998 as a Danish nation-wide study of 4,314 twins randomly selected from the consecutive birth cohorts of 1931-1952. In 2008-2011 a follow-up study was performed on all eligible twin pairs originally enrolled (Pedersen et al, 2019). Zygosity was established by four questions regarding physical similarity, which correctly classified more than 95% of the pairs (Christiansen et al, 2003).…”