Original Articles
The interaction of prematurity with genetic and environmental influences on cognitive development in twins,☆☆

https://doi.org/10.1067/mpd.2000.108445Get rights and content

Abstract

Objective: To investigate how the degree of prematurity interacts with genetic and environmental influences in their effect on verbal and nonverbal cognitive development. Study design: The target sample consisted of more than 2000 pairs of twins born in England and Wales in 1994. At 24 months, measures of verbal and non-verbal cognitive development were obtained from the twins’ parents. The sample was divided into 3 groups according to degree of prematurity: very preterm or high-risk (<32 weeks), moderately preterm or medium-risk (32-33 weeks), and mildly preterm/term or low-risk (>34 weeks). Quantitative genetic analyses were used to assess the contributions of genetic and environmental influences on vocabulary and cognitive development. Results: The results indicated gene-environment interactions. For the high-risk group, genetic effects on both verbal and non-verbal cognitive ability were completely overshadowed by shared environmental factors, whereas for both medium- and low-risk groups, additive genetic effects explained 18% to 33% of the variance. Conclusions: Our findings indicate that genetic factors are not responsible for cognitive outcomes of very preterm infants and suggest that early environmental influences appear to affect verbal and non-verbal cognitive development at 2 years of age. (J Pediatr 2000;137:527-33)

Section snippets

Methods

The sampling frame for this study, the Twins Early Development Study, consisted of all twins born in England and Wales in 1994.14 Unlike previous reports,14, 15, 16 this study included twins who were born very premature.

The initial target sample consisted of 3452 families who returned both background information on the twins and their families and test booklets for each twin, which included the cognitive measure and the vocabulary measure described below. At each stage of the study (ie, when

Descriptive Statistics

Fig 1 compares the mean standardized scores for both verbal and non-verbal cognitive measures for high-, medium-, and low-risk groups.

. Mean standardized scores for total sample at 2 years for language development (MCDI) and cognitive performance (PARCA) by gestational risk category.

The data show a linear relationship between degree of prematurity and mean performance on both outcome measures. These findings are in line with previous reports, which have consistently demonstrated delayed

Discussion

The results of this study are an example of significant genotypeenvironment interactions in humans. Gene-environment interaction refers to genetic differences in sensitivity or susceptibility to environments.13 In this study, gene-environment interaction refers to the interaction between the environmental trauma of prematurity and the magnitude of genetic effects. We found that individual differences in 2-year-old cognitive outcomes of very premature birth are not due to genetic factors. This

References (32)

  • AA Brooks et al.

    Birth weight: Nature or nurture?

    Early Hum Dev

    (1995)
  • AA Baumeister et al.

    A critical analysis of the infant health and development program

    Intelligence

    (1996)
  • NS. Paneth

    The problem of low birth weight

    Future Child

    (1995)
  • D Wolke et al.

    Cognitive status, language attainment, and pre-reading skills of 6-year-old very preterm children and their peers: the Bavarian Longitudinal Study

    Dev Med Child Neurol

    (1999)
  • N Botting et al.

    Cognitive and educational outcome of very-low-birthweight children in early adolescence

    Dev Med Child Neurol

    (1998)
  • MB Resnick et al.

    Educational disabilities of neonatal intensive care graduates

    Pediatrics

    (1998)
  • HG Taylor et al.

    Predictors of early school age outcomes in very low birth weight children

    J Dev Behav Pediatr

    (1998)
  • AH Whitaker et al.

    Neonatal cranial ultrasound abnormalities in low birth weight infants: relation to cognitive outcomes at six years of age

    Pediatrics

    (1996)
  • D. Wolke

    Language problems in neonatal at risk children: towards an understanding of developmental mechanisms [invited comment]

    Acta Paediatr

    (1999)
  • NJ Sebire et al.

    Dichorionic twins discordant for intrauterine growth retardation

    Arch Dis Child Fetal Neonatal Ed

    (1997)
  • M Laucht et al.

    Developmental outcome of infants born with biological and psychosocial risks

    J Child Psychol Psychiatry

    (1997)
  • WA. Silverman

    Overtreatment of neonates? A personal retrospective

    Pediatrics

    (1992)
  • M Bendersky et al.

    Environmental risk, biological risk and developmental outcome

    Dev Psychol

    (1994)
  • R Plomin et al.

    Behavioral genetics

    (1997)
  • PS Dale et al.

    Genetic influence on language delay in two-year-old children

    Nat Neurosci

    (1998)
  • TC Eley et al.

    Genetic and environmental origins of verbal and performance components of cognitive delay in two-year-olds

    Dev Psychol

    (1999)
  • Cited by (34)

    • Low birth weight and risk of affective disorders and selected medical illness in offspring at high and low risk for depression

      2007, Comprehensive Psychiatry
      Citation Excerpt :

      In some twin studies, the interaction of familial history of psychopathology and BW status has been tested. One study found no evidence for a synergistic interaction of BW and parent psychopathology on child psychopathology [34], but other studies reported an antagonistic interaction, in which children with LBW (adjusted for gestational age), compared to those with normal BW, were less sensitive to familial or genetic effects on increased risk of behavioral problems [37] and cognitive development [38]. Twin studies have a methodologic strength over community and/or epidemiologic studies in controlling for extraneous effects.

    • Environmental moderators of genetic influence on verbal and nonverbal abilities in early childhood

      2005, Intelligence
      Citation Excerpt :

      This will be considered in more detail in the Discussion. The results for twin medical risk show the opposite pattern in that group heritability was lower with increased risk, especially at the extremes, a result supporting that found by Koeppen-Schomerus et al. (2000). Educational toys in the home and SES did not yield a systematic pattern of results.

    View all citing articles on Scopus

    This research is part of the Twins’ Early Development Study (TEDS) which is supported by a program grant from the Medical Research Council (UK).

    ☆☆

    Reprints not available from author.

    View full text