Genetic contributions to the association between height and intelligence: Evidence from Dutch twin data from childhood to middle age

A positive association between intelligence (IQ) and height has been reported previously. It is generally assumed that this association reflects the effect of childhood environment on IQ, but there is still little research supporting directly this hypothesis. We studied the association between height and IQ in 209 Dutch twin pairs at the ages of 5, 7, 10 and 12 years, 208 twin pairs at 16 and 18 years of age and 567 twin pairs and their siblings in adulthood. The heritability of height was high in all cohorts and across all ages (a² = 0.93 − 0.96). In adulthood, heritability was also high for full-scale IQ (FSIQ: a² = 0.83–0.84) and somewhat lower for verbal IQ (VIQ: a² = 0.66–0.84). In early childhood, the heritability was lower, and common environmental factors had a substantial effect on FSIQ and VIQ. A positive association of height and IQ was found in early childhood and adolescence. In adulthood, a correlation was found between height and FSIQ in young adulthood and between height and VIQ in middle age. All correlations could be ascribed to genetic factors influencing both height and IQ. Thus, these results show that the association between height and IQ should not be directly regarded as evidence for childhood living conditions affecting IQ, but the effect of genetic factors affecting independently or interacting with environmental factors should be considered as well.     

Genetic and environmental contributions to pro-social attitudes: a twin study of social responsibility

Although 51 twin and adoption studies have been performed on the genetic architecture of antisocial behaviour, only four previous studies have examined a genetic contribution to pro-social behaviour. Earlier work by the author with the University of London Institute of Psychiatry Adult Twin Register found that genes contributed approximately half of the variance to measures of self-report altruism, empathy, nurturance and aggression, including acts of violence. The present study extends those results by using a 22-item Social Responsibility Questionnaire with 174 pairs of monozygotic twins and 148 pairs of dizygotic twins. Forty-two per cent of the reliable variance was due to the twins' genes, 23% to the twins' common environment and the remainder to the twins' non-shared environment.     

The relationship between brain weight and head circumference from birth to age 18 years

A relation between head circumference and brain weight of humans is generally believed to exist, but the literature contains only two studies which exhibit a quantitative aspect of the relation, showing that brain weight is proportional to the cube of the head circumference from birth through age 3.5 years. By assembling data from autopsy records, we have been able to show that this cubic relationship holds through brain maturation at around age 18 years.     

The cognitive and identity development of twins at 16 years of age: a follow-up study of 32 twin pairs.

This is a follow up study of twins within the Stockholm area, including 32 families and their twins attending grade nine. The twins have been followed from birth to 16 years of age. The main purpose of this study from its inception was to assess mental and cognitive development at different ages. Another aim was to see how the twins who were born prematurely are developing during the school ages. A third aim has been to gain a deeper insight into the relationship between co-twins and the development of their identities, which is the focus of this paper. Several ability tests have been used, as well as questionnaires about interests, attitudes toward school, and leisure activities. At the 16-year follow-up, a psychological method, the Wartegg drawing test, designed to examine identity, ego strength, dependency, ambition, anxiety, willpower, creativity, empathy and coping strategies has been used. The results indicate that it is difficult for twins to develop independence and a positive identity, as they have to emancipate themselves both from their parents and from their co-twins. Some differences in identity, anxiety and ambition were observed between female and male twins, MZ and DZ twins, preterm and fullterm twins. Prematurity, sex and zygosity no longer had any relation to cognitive development at 16 years of age.     

Length and weight in rural Guatemalan Ladino children: birth to seven years of age.

The present study reports 5,029 length and weight measurements as well as percentile distributions for a mixed longitudinal series of 1,119 rural Guatemalan Ladino children. The study sample, birth through seven years, is representative of children in clinically good health, but of suboptimal nutrition. Boys are longer and heavier than girls over the age range. Guatemalan children of both sexes are smaller than American white children from Denver. Differences are least at birth, and increase through two years of age. Between two and five years, differences between the rural Guatemalan Ladino and Denver samples are rather stable, but then increase through seven years. Despite these differences there is a linear weight for length relationship which is the same across all preschool ages, both sexes, and for both the Guatemalan and Denver populations. This implies that age, sex, ethnic differences between the two groups compared, and mild-to-moderate protein-calorie malnutrition do not affect the relationship between weight and length in preschool children.     

Investigating unique environmental contributions to the neural representation of written words: a monozygotic twin study

The visual word form area (VWFA) is a region of left inferior occipitotemporal cortex that is critically involved in visual word recognition. Previous studies have investigated whether and how experience shapes the functional characteristics of VWFA by comparing neural response magnitude in response to words and nonwords. Conflicting results have been obtained, however, perhaps because response magnitude can be influenced by other factors such as attention. In this study, we measured neural activity in monozygotic twins, using functional magnetic resonance imaging. This allowed us to quantify differences in unique environmental contributions to neural activation evoked by words, pseudowords, consonant strings, and false fonts in the VWFA and striate cortex. The results demonstrate significantly greater effects of unique environment in the word and pseudoword conditions compared to the consonant string and false font conditions both in VWFA and in left striate cortex. These findings provide direct evidence for environmental contributions to the neural architecture for reading, and suggest that learning phonology and/or orthographic patterns plays the biggest role in shaping that architecture.     

Cross-sectional study of height and weight in the population of Andalusia from age 3 to adulthood

Background and objectives

In Andalusia there were no studies including a representative sample of children and adolescent population assessing growth and weight increase. Our objectives were to develop reference standards for weight, height and BMI for the Andalusian pediatric population, from 3 to 18 years of age for both genders, and to identify the final adult height in Andalusia.

Subjects and methods

Two samples were collected. The first included individuals from 3 to 18 years of age (3592 girls and 3605 boys). They were stratified according type of study center, size of population of origin, age (32 categories of 0.5 years) and gender, using cluster sampling. Subjects from >18 to 23 years of age (947 women and 921 men) were sampled in 6 non-university educational centers and several university centers in Granada. Exclusion criteria included sons of non-Spanish mother or father, and individuals with chronic conditions and/or therapies affecting growth. Two trained fellows collected the data through February to December 2004, for the first sample, and through January to May 2005, for the second.Reference curves were adjusted using Cole's LMS method, and the quality of the adjustment was assessed using the tests proposed by Royston. In addition, a sensitivity analysis was applied to the final models obtained.

Results

Data for 9065 cases (4539 women and 4526 men) were obtained; 79.39% (n = 7197) in the up to 18 years of age group. In the first sampling only 0.07% (3 girls and 2 boys) refused to participate in the study. In addition, 327 students (4.5%) were absent when sampling was done. We present mean and standard deviation fort height, weight and BMI at 0.5 years intervals, from 3 to 23 years of age, for both genders. After adjustment with the different models, percentiles for height, weight (percentiles 3, 5, 10, 25, 50, 75, 90, 95, and 97) and BMI (percentiles 3, 5, 50, 85, 95, and 97) are presented for both genders.

Conclusion

This is the first study in Andalusia with a representative sample from the child-juvenile population to investigate weight, height and BMI in subjects from 3 to 23 years of age. The great variability observed in the values from sample of 18 to 23 years of age individuals, ensures the inclusion of extreme values, although random sampling was not used. There still is a lack of standard reference values for the Andalusian population younger done 3 years of age.

     

Genetic and environmental influences on infant growth: prospective analysis of the Gemini twin birth cohort

Objective

Infancy is a critical period during which rapid growth potentially programs future disease risk. Identifying the modifiable determinants of growth is therefore important. To capture the complexity of infant growth, we modeled growth trajectories from birth to six months in order to compare the genetic and environmental influences on growth trajectory parameters with single time-point measures at birth, three and six months of age.

Methods

Data were from Gemini, a population sample of 2402 UK families with twins. An average 10 weight measurements per child made by health professionals were available over the first six months. Weights at birth, three and six months were identified. Longitudinal growth trajectories were modeled using SITAR utilizing all available weight measures for each child. SITAR generates three parameters: size (characterizing mean weight throughout infancy), tempo (indicating age at peak weight velocity (PWV)), and velocity (reflecting the size of PWV). Genetic and environmental influences were estimated using quantitative genetic analysis.

Results

In line with previous studies, heritability of weight at birth and three months was low (38%), but it was higher at six months (62%). Heritability of the growth trajectory parameters was high for size (69%) and velocity (57%), but low (35%) for tempo. Common environmental influences predominated for tempo (42%).

Conclusion

Modeled growth parameters using SITAR indicated that size and velocity were primarily under genetic influence but tempo was predominantly environmentally determined. These results emphasize the importance of identifying specific modifiable environmental determinants of the timing of peak infant growth.     

Genetic and environmental contributions to age at menarche: Interactive effects of father absence and LIN28B

Substantial research and theory over a number of years have linked father absence to earlier age at menarche (AAM). More recent work has centered on explaining the relative genetic and environmental contributions to this correlation. The purpose of the current study was to evaluate the combined effects of father absence and variation in the LIN28B gene on AAM. A sample of 300 women (age 18–25) successfully genotyped for two LIN28B single nucleotide polymorphisms (SNPs; rs364663 and rs314273) were used to test gene-environment interaction models. Results for both SNPs were consistent with the hypothesis that father absence would attenuate later AAM associated with LIN28B. Genetic index analysis of combined LIN28B SNPs showed that girls with at least one copy of the T/T genotype had later AAM if they were father present. Study strengths and the implications of GxE research for life history models are discussed.     

Complex segregation analysis of body height,weight and BMI in pedigree data from Middle Dalmatia,Croatia

It has recently been reported that the mode of inheritance of body height, weight and BMI in five ethnically and geographically different populations can be described in terms of a major gene (MG) model. Here, using the pedigree sample from the island populations of Middle Dalmatia, Croatia (1,312 observed individuals in 462 pedigrees), the evidence is presented that supports the above findings. By applying the usual transmission probability tests, the hypothesis has been accepted that a significant part of the variation of each one of those three basic morphological traits can be attributed to the effect of a putative large-effect gene. The effect of a putative MG is responsible for 39-50% of age and sex adjusted trait's variation and for 34-48% of the total (non age-adjusted) variation of height, weight and BMI.     

The 48,XXXX syndrome: study of psychomotor development from birth to 11 years of age and review of the literature

A child with four X chromosomes is described. This case and the literature review allow to underline the mental retardation and some other "major" but inconstant signs that are extremely helpful for the early clinical diagnosis. They are hypertelorism, epicanthal fold and genital anomalies. The mental evolution is assessed on an eleven year period. The bad results concern particularly the child's use of language and the complicated works. They become worse with time. The additional X chromosomes Mary Lyon inactivation, perhaps incomplete, is discussed because its determinism. Enzymatic measuring out is our approach to this problem.     

Genetic study of the height and weight process during infancy.

Longitudinal height and weight data from 4649 Dutch twin pairs between birth and 2.5 years of age were analyzed. The data were first summarized into parameters of a polynomial of degree 4 by a mixed-effects procedure. Next, the variation and covariation in the parameters of the growth curve (size at one year of age, growth velocity, deceleration of growth, rate of change in deceleration [i.e., jerk] and rate of change in jerk [i.e., snap]) were decomposed into genetic and nongenetic sources. Additionally, the variation in the estimated size at birth and at 2 years of age interpolated from the polynomial was decomposed into genetic and nongenetic components. Variation in growth was best characterized by a genetic model which included additive genetic, common environmental and specific environmental influences, plus effects of gestational age. The effect of gestational age was largest for size at birth, explaining 39% of the variance. The differences between monozygotic and dizygotic twin correlations were largest for size at 1 and 2 years of age and growth velocity of weight, which suggests that these parameters are more influenced by heritability than size at birth, deceleration and jerk. The percentage of variance explained by additive genetic influences for height at 2 years of age was 52% for females and 58% for males. For weight at 2 years of age, heritability was approximately 58% for both sexes. Variation in snap height for males was also mainly influenced by additive genetic factors, while snap for females was influenced by both additive genetic and common environmental factors. The correlations for the additive genetic and common environmental factors for deceleration and snap are large, indicating that these parameters are almost entirely under control of the same additive genetic and common environmental factors. Female jerk and snap, and also female height at birth and height at 2 years of age, are mostly under control of the same additive genetic factor.     

Genetic and environmental contributions to the winter hardiness of conifers

Summary

Both genetic and environmental components are involved in the processes of winter hardening and dehardening which permit needles of conifers like Norway spruce to survive very low temperatures (< - 30°C) over winter and to recover fully in time for the following and subsequent seasons. One of the major environmental effects of increasing concentrations of atmospheric ozone (O₃) in recent summers has been to affect detrimentally the ability of conifer needles to harden properly and at the correct rate the following autumn. Part of the mechanism by which this occurs in the cytoplasm of needle cells has been traced to detrimental effects on both the Δ¹² fatty acid desaturase and the unusual Δ⁵ desaturase which appears to be part of the low temperature survival mechanism of conifers. The genetic component of winter hardening also involves needle lipids. Studies of lipids in the needles of Norway spruce trees of different provenances growing for many years in the UK have shown that they change during winter hardening as though they were still on trees in the original sites throughout Europe from which the seeds of these trees were initially collected.     

Genetic and environmental contributions to the variance of body height in a sample of first and second degree relatives.

Height was measured in a health screening of the population in Nord-Trøndelag, Norway. Correlations were computed for 24,281 pairs of spouses, 43,613 pairs of parents and offspring, 19,168 pairs of siblings, 1,318 pairs of grandparents and grandchildren, 1,218 cognate avuncular pairs, 849 noncognate avuncular pairs, 175 pairs of same-sexed twins, and smaller groups of other types of relatives. Fitting of structural equation models showed proportions of additive genetic variance of approximately 0.8 for both sexes and small sex-specific effects that probably reflect genetic dominance or environmental sibling effects. The correlations between parents and offspring were significantly lower in old than young cohorts, seeming to imply some kind of interaction effect between genes and environment. © 1992 Wiley-Liss, Inc.