Academic achievement of twins and singletons in early adulthood: Taiwanese cohort study

Abstract

Objectives To examine the long term effects of low birth weight on academic achievements in twins and singletons and to determine whether the academic achievement of twins in early adulthood is inferior to that of singletons. Design Cohort study. Setting Taiwanese nationwide register of academic outcome. Participants A cohort of 218 972 singletons and 1687 twins born in Taiwan, 1983-5. Main outcome measure College attendance and test scores in the college joint entrance examinations. Results After adjustment for birth weight, gestational age, birth order, and sex and the sociodemographic characteristics of the parents, twins were found to have significantly lower mean test scores than singletons in Chinese, mathematics, and natural science, as well as a 2.2% lower probability of attending college. Low birthweight twins had an 8.5% lower probability of college attendance than normal weight twins, while low birthweight singletons had only a 3.2% lower probability. The negative effects of low birth weight on the test scores in English and mathematics were substantially greater for twins than for singletons. The twin pair analysis showed that the association between birth weight and academic achievement scores, which existed for opposite sex twin pairs, was not discernible for same sex twin pairs, indicating that birth weight might partly reflect other underlying genetic variations. Conclusions These data support the proposition that twins perform less well academically than singletons. Low birth weight has a negative association with subsequent academic achievement in early adulthood, with the effect being stronger for twins than for singletons. The association between birth weight and academic performance might be partly attributable to genetic factors.

No Evidence of Genetic Mediation in the Association Between Birthweight and Academic Performance in 2,413 Danish Adolescent Twin Pairs

“…Early postnatal catch-up growth may require more energy thereby draining resources from neural development and consequently have a negative influence on the cognitive development. Other studies of twins propose that part of the positive association between birthweight and IQ may be mediated through genetic effects and consequently noncausal (Boomsma et al, 2001;Tsou et al, 2008).…”

“…A Dutch study of 170 twin pairs tested 4 times in the age range 5-12 found a significant positive association between differences in birthweight and differences in IQ at age 7 and at age 10 within DZ pairs, but no similar associations within MZ pairs (Boomsma et al, 2001). In a recent study of 316 same-sex and 61 opposite-sex Taiwanese twin pairs (Tsou et al, 2008), the authors found a positive within-pair association birthweight and both mathematics and English test scores in opposite-sex twin pairs but not in same-sex twin pairs; the authors did not have access to zygosity information. Failure to observe within pair associations between measures of cognitive functioning and birthweight in MZ pairs in the Dutch study (Boomsma et al, 2001) and same-sex pairs in the Taiwanese study (Tsou et al, 2008) led the researchers to conclude that their results imply that the birthweight-IQ association is partly due to genetic confounding, that is, that common genetic factors are influencing both fetal growth and IQ.…”

“…Various studies have analyzed the association between within twin-pair differences in IQ and birthweight both in epidemiology (Boomsma et al, 2001;Newcombe et al, 2007;Tsou et al, 2008) as well as in economics (Behrman & Rosenzweig, 2006;Black et al, 2007;Royer, 2009). Studies of non-twin siblingpair differences (Lawlor et al, 2005;Lawlor et al, 2006;Matte et al, 2001) No Genetic Mediation -Birthweight and School Achievement mechanism behind the birthweight-IQ association.…”

Twin–Singleton Differences in Cognitive Abilities in a Sample of Africans in Nigeria

“…However, the findings of the Tsou et al (2008) study are not consistent with those of a similar population-based study conducted in Denmark (Christensen et al, 2006). The Danish study compared academic performance of adolescent twins and singletons (age 15 or 16) born between 1986 and 1988 and reported that differences in academic performance between the two groups were negligible after the data were adjusted for various confounding factors such as birth weight and gestational age.…”

Twin Specific Risk Factors in Primary School Achievements

“…Only a few studies have looked at the differences in educational achievement between twins and singletons. A 1983-1985 birth cohort study from Taiwan found that twins had lower scores and were less likely to attend college, even when the data were adjusted for birth weight, gestational age, birth order within the family, sex, and socioeconomic status (Tsou, Tsou, Wu, & Liu, 2008). The scores of Dutch female twins on an educational achievement test were also lower than those of singleton controls from the the same grade and those of an older brother or sister.…”