TEDS Data Dictionary

CoTEDS: Children of Twins Study

Contents of this page:

Introduction

The Children of TEDS (CoTEDS) Study started enrolling participants in 2016. Participants are TEDS twins, their children, and the coparents of those children. Potential participants have largely been identified through TEDS questionnaires such as TEDS21, TEDS26 and TEDS30. In these questionnaires, twins were asked whether they had children (or were expecting children), then were asked if they would like to enrol in CoTEDS. This process of enrolment via TEDS is ongoing, and will continue for the foreseeable future.

An enrolled twin may have one or more children in CoTEDS. When each child reaches the appropriate age, as listed below, the twin (parent) is asked to complete a questionnaire. As part of this process, the twin is then asked to invite the second parent (coparent) of the child to enrol, and the coparent is also then asked to complete a questionnaire. These questionnaire data collections will continue for all newly enrolled participants.

In addition to questionnaire data, CoTEDS is collecting DNA samples for genotyping. Enrolled twins are asked to collect and return DNA samples for each of their children in CoTEDS. Each coparent is also asked to enrol for DNA collection. The twins themselves are asked for their DNA, in cases where twins have not already been genotyped in TEDS.

This page provides only a brief outline of the CoTEDS study. It is anticipated that links to a CoTEDS data dictionary, when available, will appear on this page, providing further details of data collection methods, together with detailed documentation of questionnaires and dataset variables.

CoTEDS data collections

Recruitment of new twins, children and coparents into the CoTEDS study is ongoing, and new questionnaires have been added as the children have grown older. At the time of writing, the following data collections are underway.

Data collection Child age Comments Year started
Twin Wave 1 questionnaire
(full version)		 1 year old:
between 12 and 21 months.		 The age range is designed to avoid overlap with wave 2.
This was designed to be the baseline data collection for each child.		 2017
Twin Wave 1 questionnaire
(truncated version)		 4+ years old:
51 months or older.		 This age range is designed to avoid overlap with wave 3.
This shorter version of the wave 1 questionnaire is designed to capture the most essential baseline data, for children who were recruited at a later age.		 2017
Twin Wave 2 questionnaire 2 years old:
between 24 and 33 months.		 This age range is designed to avoid overlap with waves 1 and 3. 2018
Twin Wave 3 questionnaire 3 years old:
between 36 and 47 months.		 This age range is designed to avoid overlap with wave 2. 2022
Coparent Wave 1 questionnaire 1 year old:
between 12 and 21 months.		 Only sent if a coparent has been enrolled for questionnaires, following completion of the twin wave 1 questionnaire. 2017
Coparent Wave 2 questionnaire 2 years old:
between 24 and 33 months.		 Only sent if a coparent has been enrolled for questionnaires. 2018
Coparent Wave 3 questionnaire 3 years old:
between 36 and 47 months.		 Only sent if a coparent has been enrolled for questionnaires. 2022
Child DNA 1 year or older. The twin (parent) is asked for the child's DNA if the twin has completed wave 1 for the same child, and the twin has enrolled for DNA collection. 2023
Coparent DNA - Coparent has enrolled for DNA collection. 2023
Twin DNA - Twin has not already been genotyped (nor has their cotwin if MZ), and twin has enrolled for DNA collection. 2023

Questionnaire data are being collected electronically, with the alternative option of a paper questionnaire for twins (but not coparents). Email and phone reminders are used to encourage unresponsive twins and coparents. For each data collection, each twin (or coparent) is offered a £10 electronic Flexecode voucher on completion of the questionnaire or return of a DNA sample. Additional rewards such as CoTEDS t-shirts are sent on return of the twin questionnaires.

CoTEDS data sharing

A more specific statement about the sharing of CoTEDS questionnaire data will appear here when a CoTEDS data sharing policy has been formulated. A link or links to a CoTEDS data dictionary will also appear on this page when available.

All data collections, as tabulated above, are ongoing, as is the recruitment of new families into the CoTEDS study. Raw data Ns are growing, the largest Ns being for the twin wave 1 questionnaire as this was the first data collection started, and because data are collected for the youngest children. It is likely that dated "data freezes" will be established for each questionnaire dataset.

CoTEDS questionnaire datasets, when made available, will be made anonymous before sharing, in the same way as the TEDS datasets. Anonymisation involves assigning randomised IDs both to children and to the twins linked in the same dataset, as well removal of direct or indirect identifiers, and the replacement of dates with ages.

Whereas TEDS twin datasets are structured with one row of data per twin, there may be one, two or more rows of data per twin in a CoTEDS per-child dataset. Decisions about how to merge TEDS and CoTEDS datasets for analysis may depend on the nature of the analysis.

The default policy for sharing DNA and genotypic data will be the same for CoTEDS as for TEDS: see the DNA page.

CoTEDS background variables

The IDs used for twins and their children are described in the scrambled IDs page. Other CoTEDS-related background variables are also listed on the TEDS background variables page.

The following per-twin variables are now available from TEDS, for twins who have enrolled in CoTEDS:

  • coteds: flag variable indicating whether the twin is enrolled in CoTEDS (1=yes, 0=no)
  • cotedschildren: number of children enrolled in CoTEDS (1, 2, etc). Only available for twins enrolled in CoTEDS.
  • cotedsagechl: age of twin when the first recorded child was born (years).
    Only available for twins enrolled in CoTEDS.
    Analagous to the amagechl variable in the TEDS 1st Contact dataset.

When CoTEDS per-child questionnaire datasets are made available, each child will have the following background variables in the dataset:

  • birthorder: the birth order of the child from the given twin parent (1=first born, 2=second born, etc)
  • childsex: the child's sex (0=female, 1=male)
  • childtwin: flags whether or not the child is a twin (0=no, 1=yes)
  • A data flag for each CoTEDS data collection in the dataset (1=data present, 0=data not present).
  • Child age (years), for each CoTEDS data collection in the dataset