Genetics of pre-pubertal growth: A longitudinal study of Japanese twins

Heritability of Psychological Traits and Developmental Milestones in Infancy: A Systematic Review and Meta-analysis

IMPORTANCE

Although infancy is the most rapid period of postnatal growth and development, factors associated with variation in infant traits are not well understood.

OBJECTIVE

To synthesize the large twin study literature partitioning phenotypic variance in psychological traits and developmental milestones in infancy into estimates of heritability and shared and nonshared environment.

DATA SOURCES

PubMed, PsycINFO, and references of included publications were searched up to February 11, 2021.

STUDY SELECTION

Peer-reviewed publications using the classical twin design to study psychological traits and developmental milestones from birth to 2 years old were included.

DATA EXTRACTION AND SYNTHESIS

Data were extracted in line with Preferred Reporting Items for Systematic Reviews and Meta-Analyses and categorized using the International Classification of Functioning, Disability and Health: Children and Youth Version. Data were pooled in 3-level random effects models, incorporating within-cohort variance in outcome measurement and between-cohort variance. Data were analyzed from March 2021 through September 2021.

MAIN OUTCOMES AND MEASURES

The primary outcomes were monozygotic and dizygotic twin correlations. These were used to calculate genetic and shared and nonshared environment estimates.

RESULTS

Among 139 publications that were systematically retrieved, data were available on 79 044 twin pairs (31 053 monozygotic and 47 991 dizygotic pairs), 52 independent samples, and 21 countries. Meta-analyses were conducted on psychological traits and developmental milestones from 106 publications organized into 10 categories of functioning, disability, and health. Moderate to high genetic estimates for 8 categories were found, the highest of which was psychomotor functions (pooled h2, 0.59; 95% CI, 0.25-0.79; P < .001). Several categories of traits had substantial shared environment estimates, the highest being mental functions of language (pooled c2, 0.59; 95% CI, 0.24-0.86; P = .001). All examined categories of traits had moderate or high nonshared environment estimates, the highest of which were emotional functions (pooled e2, 0.42; 95% CI, 0.33-0.50; P < .001) and family relationships (pooled e2, 0.42; 95% CI, 0.30-0.55; P < .001).

CONCLUSIONS AND RELEVANCE

These findings may be an important source of information to guide future gene discovery research, public perspectives on nature and nurture, and clinical insights into the degree to which family history and environments may estimate major domains of infant functioning, disability, and health in psychological traits and developmental milestones.

The New West Japan Twins and Higher Order Multiple Births Registry

The new West Japan Twins and Higher Order Multiple Births Registry was established by recruiting young twins and multiple births and by referrals from public health centers in the 1990s. The participants included in the survey comprised over 7800 twins and 4241 higher order multiples, and their families. Specifically, the present registry contains one of the largest triplet samples in the world. For these twins and multiples, data on year of delivery, mode of delivery, gestational age, intrapartum complications, longitudinal physical measures, motor milestones, cerebral palsy and feeding methods were obtained from records in the Maternal and Child Health Handbooks and schools. Participating mothers were asked to indicate family structure, parental educational history, maternal sleeping time, maternal health condition, maternal and paternal age at multiple delivery, complications during pregnancy, handedness of multiples and age at menarche of multiples. However, the zygosity differed among the various collaborating public health centers according to factors such as the time of investigation. Follow-up questionnaires have been mailed out every 3-4 years for longitudinal studies. This article describes the goals of this registry, recruitment of multiples and the focus of the study. The goals of this registry are not only to conduct research on human genetics and maternal and child health, but also to contribute to providing appropriate information for families with multiples.

Environmental rather than genetic factors determine the variation in the age of the infancy to childhood transition: a twins study

OBJECTIVE

Using a twins study, we sought to assess the contribution of genetic against environmental factor as they affect the age at transition from infancy to childhood (ICT).

STUDY DESIGN

The subjects were 56 pairs of monozygotic twins, 106 pairs of dizygotic twins, and 106 pairs of regular siblings (SBs), for a total of 536 children. Their ICT was determined, and a variance component analysis was implemented to estimate components of the familial variance, with simultaneous adjustment for potential covariates.

RESULTS

We found substantial contribution of the common environment shared by all types of SBs that explained 27.7% of the total variance in ICT, whereas the common twin environment explained 9.2% of the variance, gestational age 3.5%, and birth weight 1.8%. In addition, 8.7% was attributable to sex difference, but we found no detectable contribution of genetic factors to inter-individual variation in ICT age.

CONCLUSIONS

Developmental plasticity impacts much of human growth. Here we show that of the ∼50% of the variance provided to adult height by the ICT, 42.2% is attributable to adaptive cues represented by shared twin and SB environment, with no detectable genetic involvement.

Faster increase in body mass index between ages 8 and 13 is associated with risk factors for cardiovascular morbidity and mortality

BACKGROUND AND AIMS

Excess childhood weight is associated with cardiovascular disease (CVD) in adulthood. Whether this is mediated through adult body mass index (BMI) and associated risk factors such as metabolic derangements remains unclear. The aim was to examine whether childhood BMI velocity (Δkg m(-2) per year) was associated with adult CVD mortality and to examine how adult BMI and cardiometabolic risk factors contribute to the association.

METHODS AND RESULTS

Subjects were 1924 Icelanders born between 1921 and 1935 and living in Reykjavik when recruited into a longitudinal study from 1967 to 1991. From ages 8-13 years, BMI velocity was calculated to quantify the association between childhood growth and adult CVD mortality. Deaths from recruitment to 31 December 2009 were extracted from the national register. There were 202 CVD deaths among men and 90 CVD deaths among women (mean follow-up: 25.9 years). Faster BMI velocity from ages 8-13 years was associated with CVD mortality when comparing those in the highest versus lowest tertile with corresponding hazard ratio (HR) (95% confidence interval (CI)): 1.49 (1.03, 2.15) among men and 2.32 (1.32, 4.08) among women after adjustment for mid-life BMI and CVD risk factors. Faster childhood BMI velocity was associated with elevated CVD risk factors among men at mid-life but these associations were less pronounced among women.

CONCLUSION

Faster increase in BMI from ages 8-13 years was associated with an increased CVD mortality risk. Children with early growth spurts coupled with excess weight gain during this transition period from childhood into adolescence should be closely monitored to ensure better health in adulthood.

Genetic and environmental influences on chest circumference during infancy: a longitudinal study of japanese twins

BACKGROUND

Chest circumference (CC) is suggested to be a good indicator of early life nutrition, but little is known on the heritability of CC. Thus we analysed the effects of genetic and environmental factors on the development of CC in Japanese infants.

METHODS

CC was measured longitudinally from birth until 1 year of age in a cohort of 211 monozygotic and 160 dizygotic complete Japanese twin pairs born in 1989-2002. The data were analysed using applications of structural linear equation modelling for twin data.

RESULTS

No sex-specific differences in the variance components were found. Environmental factors unique to each twin explained the major part of the variation of CC at birth whereas environmental factors shared by co-twins were more important at 1-3 months of age. From 3 months of age, the effect of genetic factors become steadily stronger and they explained the majority of the variation at 1 year of age. Strong genetic continuity in the development of CC was found, but also new sets of genes were activated during the first year of life. The origin of the environmental part of the variation could be tracked before 3 months of age. A substantial part of common and specific environmental factors affecting CC affected also birthweight.

CONCLUSIONS

CC is sensitive to intrauterine environmental factors, but these effects diminish during the first year of life, at least if postnatal environment is good. CC can be a useful indicator when identifying newborns who have suffered suboptimal pre-natal conditions.

The West Japan Twins and Higher Order Multiple Births Registry

The West Japan Twins and Higher Order Multiple Births Registry was established in the 1990s by recruiting young twins and multiples and through referrals from public health centers. To date, over 7,000 twins and 4,300 higher order multiple births and their families have been registered in the survey, and it includes one of the largest triplet samples in the world. Follow-up questionnaires are also mailed every 2 to 3 years as part of longitudinal survey studies. This article describes the goals of the registry, the recruitment of multiples, and the overall focus of the study. The goals of the registry are not only to provide data for research on human genetics and maternal and child health, but also to provide appropriate information for families with multiples.