T.J. Glasner

The Young Netherlands Twin Register (YNTR): Longitudinal Twin and Family Studies in Over 70,000 Children

The Netherlands Twin Register (NTR) began in 1987 with data collection in twins and their families, including families with newborn twins and triplets. Twenty-five years later, the NTR has collected at least one survey for 70,784 children, born after 1985. For the majority of twins, longitudinal data collection has been done by age-specific surveys. Shortly after giving birth, mothers receive a first survey with items on pregnancy and birth. At age 2, a survey on growth and achievement of milestones is sent. At ages 3, 7, 9/10, and 12 parents and teachers receive a series of surveys that are targeted at the development of emotional and behavior problems. From age 14 years onward, adolescent twins and their siblings report on their behavior problems, health, and lifestyle. When the twins are 18 years and older, parents are also invited to take part in survey studies. In sub-groups of different ages, in-depth phenotyping was done for IQ, electroencephalography , MRI, growth, hormones, neuropsychological assessments, and cardiovascular measures. DNA and biological samples have also been collected and large numbers of twin pairs and parents have been genotyped for zygosity by either micro-satellites or sets of short nucleotide polymorphisms and repeat polymorphisms in candidate genes. Subject recruitment and data collection is still ongoing and the longitudinal database is growing. Data collection by record linkage in the Netherlands is beginning and we expect these combined longitudinal data to provide increased insights into the genetic etiology of development of mental and physical health in children and adolescents.

Applications of calendar instruments in social surveys: a review

Retrospective reports in survey interviews and questionnaires are subject to many types of recall error, which affect completeness, consistency, and dating accuracy. Concerns about this problem have led to the development of so-called calendar instruments, or timeline techniques. These aided recall procedures have been designed to help respondents gain better access to long-term memory by providing a graphical time frame in which life history information can be represented. In order to obtain more insights into the potential benefits of calendar methodology, this paper presents a review of the application of calendar instruments, their design characteristics and effects on data quality. Calendar techniques are currently used in a variety of fields, including life course research, epidemiology and family planning studies. Despite the growing interest in these new methods, their application often lacks sufficient theoretical foundation and little attention has been paid to their effectiveness. Several recent studies however, have demonstrated that in comparison to more traditional survey methods, calendar techniques can improve some aspects of data quality. While calendar instruments have been shown to be potentially beneficial to retrospective data quality, there is an apparent need for methodological research that generates more systematic knowledge about their application in social surveys.

Personal Landmarks as Recall Aids in Survey Interviews

Personal landmarks are a central element of calendar survey methods. These data collection methods use a graphical time frame in which specific landmark events can be described next to the respondents’ life history. The theoretical ideas in this article suggest that landmarks are most effective as a recall aid if they are important, domain-related, and personal events. The data originate from a calendar method that was embedded in a telephone survey in the Netherlands. The outcomes showed that respondents used a great variety of landmark events, that the number and types of landmarks are related to sociodemographic factors, and that the landmark distribution shows recency and heaping patterns. Weak positive effects of landmarks on recall accuracy were also found. The results suggest that a standardization of the landmark procedure might add to the effectiveness of its aided recall function.

Calendar Interviewing and the Use of Landmark Events – Implications for Cross-cultural Surveys

This paper discusses potential methodological issues in the design and implementation of calendar recall aids such as the Life History Calendar for cross-cultural surveys. More specifically, it aims to provide insights into how the use of landmark events in calendar interviewing may be influenced by cross-cultural variability. As an example, we compare the landmark events reported by Dutch and American respondents in two studies in which calendar recall aids were used. The study discusses differences that were found between the two countries in the numbers and types of reported landmark events, as well as in the temporal distribution of those events. The outcomes suggest that it is important for researchers to examine how landmark events in calendar instruments translate in diverse cultural contexts.

Chorionicity and Heritability Estimates from Twin Studies: The Prenatal Environment of Twins and Their Resemblance Across a Large Number of Traits

There are three types of monozygotic (MZ) twins. MZ twins can either share one chorion and one amnion, each twin can have its own amnion, or MZ twins can—like dizygotic twins—each have their own chorion and amnion. Sharing the same chorion may create a more similar/dissimilar prenatal environment and bias heritability estimates, but most twin studies do not distinguish between these three types of MZ twin pairs. The aim of this paper is to investigate the effect of chorion sharing on the similarity within MZ twin pairs for a large number of traits. Information on chorion status was obtained for the Netherlands twin register (NTR) by linkage to the records from the database of the dutch pathological anatomy national automated archive (PALGA). Record linkage was successful for over 9000 pairs. Effect of chorion type was tested by comparing the within-pair similarity between monochorionic (MC) and dichorionic (DC) MZ twins on 66 traits including weight, height, motor milestones, child problem behaviors, cognitive function, wellbeing and personality. For only 10 traits, within-pair similarity differed between MCMZ and DCMZ pairs. For traits influenced by birth weight (e.g. weight and height in young children) we expected that MC twins would be more discordant. This was found for 5 out of 13 measures. When looking at traits where blood supply is important, we saw MCMZ twins to be more concordant than DCMZ’s for 3 traits. We conclude that the influence on the MZ twin correlation of the intra-uterine prenatal environment, as measured by sharing a chorion type, is small and limited to a few phenotypes. This implies that the assumption of equal prenatal environment of mono- and DC MZ twins, which characterizes the classical twin design, is largely tenable.

Childhood ODD and ADHD Behavior: The Effect of Classroom Sharing, Gender, Teacher Gender and Their Interactions

One criterion for a diagnostic and statistical manual of mental disorders (DSM-IV) diagnosis of attention deficit hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD) is that symptoms are present in at least two settings, and often teacher ratings are taken into account. The short Conners’ Teacher Rating Scales—Revised (CTRS-R) is a widely used standardized instrument measuring ODD and ADHD behavior in a school setting. In the current study CTRS-R data were available for 7, 9 and 12-year-old twins from the Netherlands Twin Register. Measurement invariance (MI) across student gender and teacher gender was established for three of the four scales (Oppositional Behavior, Hyperactivity and ADHD Index) of the CTRS-R. The fourth scale (ATT) showed an unacceptable model fit even without constraints on the data and revision of this scale is recommended. Gene-environment (GxE) interaction models revealed that heritability was larger for children sharing a classroom. There were some gender differences in the heritability of ODD and ADHD behavior and there was a moderating effect of teacher’s gender at some of the ages. Taken together, this indicates that there was evidence for GxE interaction for classroom sharing, gender of the student and gender of the teacher.

Calendar Instruments in Retrospective Web Surveys

Calendar instruments incorporate aided recall techniques such as temporal landmarks and visual time lines that aim to reduce response error in retrospective surveys. Those calendar instruments have been used extensively in off-line research (e.g., computer-aided telephone interviews, computer assisted personal interviewing, and paper and pen interview) and have been shown to increase the quality of retrospectively collected life course data. The goal of our study was to investigate if calendar recall aids can also improve data quality in web surveys. In a methodological field experiment, we evaluated the effects of adding visual feedback and personal landmarks to our questionnaire with regard to response/break off rates, completeness of retrospective reports, interview duration, and respondent evaluations. The study included 1,451 respondents from a probability-based Internet panel who were randomly assigned to one of the four conditions of the experiment. The results indicate that in the web-based calendar tool, visual feedback properties exerted the most influence on data quality.