Sibling configuration predicts individual and descendant socioeconomic success in a modern post-industrial society

Infant inflammation predicts childhood emotional and behavioral problems and partially mediates socioeconomic disadvantage

BACKGROUND

Emotional and behavioral problems (EBP) are common in children. Environmental factors like socioeconomic disadvantage influence EBP pathogenesis and can trigger inflammation. However, the link between early inflammation-EBP in children is unclear. We investigated the associations between i) infant inflammatory biomarkers and subsequent EBP and ii) early life environmental factors and EBP and assessed whether infant inflammation mediated these associations.

METHODS

Inflammatory biomarkers glycoprotein acetyls (GlycA) and high-sensitivity C-reactive protein (hsCRP) were quantified at birth and 12 months in a population-derived birth cohort, the Barwon Infant Study. Early life factors including demographic, prenatal, and perinatal factors were collected from antenatal to the two-year period. Internalizing and externalizing problems at age two were measured by the Child Behavior Checklist. Prospective associations were examined by multivariable regression analyses adjusted for potential confounders. Indirect effects of early life factors on EBP through inflammation were identified using mediation analyses.

RESULTS

Elevated GlycA levels at birth (GlycAbirth) were associated with greater internalizing problems at age two (β = 1.32 per SD increase in GlycA; P = 0.001). Inflammation at birth had a stronger magnitude of effect with later EBP than at 12 months. GlycAbirth partially mediated the associations between lower household income (6%), multiparity (12%) and greater number of older siblings (13%) and EBP. Patterns were less evident for hsCRP or externalizing problems.

CONCLUSIONS

GlycAbirth was positively associated with EBP at age two and partially mediated the association between several indicators of socioeconomic disadvantage and EBP. Prenatal and perinatal inflammation may be relevant to early neurodevelopment and emotional health.

Early life programming of adult ischemic heart disease within and across generations: The role of the socioeconomic context

BACKGROUND

The developmental origins of ischemic heart disease (IHD) have been widely documented but little is known about their persistence across more than one generation. This study aimed to investigate whether the effects of early life disadvantages on adult IHD have changed between generations and are mediated by adult socioeconomic circumstances, and further explore the transgenerational effects of grandparental and parental exposures to disadvantaged circumstances on adult offspring's IHD.

METHODS

We used register-based data from the Uppsala Multigenerational Study, Sweden. The study populations were the parents born 1915-1929 and their offspring born 1932-1972 with available obstetric data. The offspring were further linked to grandparents who had their socioeconomic and demographic data recorded. The outcome was incident IHD assessed at ages 32-75 during a follow-up from January 1, 1964 till December 31, 2008. The exposures included birthweight standardized-for-gestational age, ponderal index, gestational length, and parental socioeconomic position (SEP). Education and income were analyzed as mediators. Potential transgenerational associations were explored by linking offspring IHD to parents' standardized birthweight and gestational length, grandparental SEP, and to grandmothers' age, parity, and marital status at parental birth. All associations were examined in Cox proportional hazard regression models.

RESULTS

Lower standardized birthweight and lower parental SEP were found to be associated with higher IHD rates in both generations, with no evidence of effect modification by generation. Education and income did not mediate the association between standardized birthweight and IHD. Disadvantaged grandparental SEP, younger and older childbearing ages of grandmothers, and paternal preterm birth affected offspring's IHD independent of parental education, income, or IHD history.

CONCLUSIONS

The findings point to similar magnitudes of IHD inequalities by early life disadvantages across two historical periods and the existence of transgenerational effects on IHD. Epigenetic dysregulation involving the germline is a plausible candidate mechanism underlying the transgenerational associations that warrant further research.

Early-life social and health determinants of adult socioeconomic position: associations and trends across generations

Background

Social and biological circumstances at birth are established predictors of adult socioeconomic position (SEP). This study aims to assess the trends in these associations across two generations and examine the effects of parental early-life characteristics on descendants’ adult SEP.

Methods

We studied men and women born in the Uppsala University Hospital 1915–1929 (G1) and their offspring born 1932–1960 (G2). Data were collected in archives and routine registers. Adult SEP was assessed as an aggregate measure combining education and occupation. The exposures were family SEP, mother’s marital status, mother’s parity, mother’s age, standardised birth weight, gestational length and birth multiplicity. Linear regression was used to examine the associations across generations.

Results

The difference in adult SEP between low and high family SEP at birth was 15.8 (95% CI: 13.3 to 18.3) percentage points smaller in G2 compared with G1, although a considerable difference was still evident in G2. The associations of adult SEP with small birth weight for gestational age, post-term birth and high parity were stable between the generations: the generational differences in adjusted coefficients were 1.5 (95% CI: −1.1 to 4.1), 0.6 (–1.7 to 2.9) and 1.8 (–0.2 to 3.8) percentage points, respectively. The association between grandparental and grandchildren’s SEPs was largely explained by parental socioeconomic conditions. Father’s preterm birth was independently associated with offspring’s SEP.

Conclusion

The stability of the associations between early-life biological disadvantages and adult SEP and the persistent, although attenuated, association between early-life and adult SEPs necessitates increased policy attention to both social and health conditions at birth.

Morphometric traits predict educational attainment independently of socioeconomic background

Background

Aim of this study is to describe the relationship between anthropometric traits and educational attainment among Estonian schoolchildren born between 1937 and 1962. We asked whether height, cranial volume and face width (a testosterone-dependent trait), measured in childhood predict later educational attainment independently of each other, family socioeconomic position (SEP) and sex. Associations between morphometric traits and education and their interactions with biosocial variables are of scholarly importance because higher education is nearly universally associated with low fertility in women, and often with high fertility in men. Hence, morphometric traits associated with educational attainment are targeted by natural selection and describing the exact nature of these associations is relevant for understanding the current patterns of evolution of human body size.

Methods

Data on morphometric measurements and family background of 11,032 Estonian schoolchildren measured between seven and 19 years of age were obtained from the study performed by Juhan Aul between 1956 and 1969. Ordinal logistic regression was used for testing the effects of morphometric traits, biosocial variables and their interaction on the cumulative probability of obtaining education beyond primary level.

Results

Of biosocial variables, family SEP was the most important determinant of educational attainment, followed by the sex, rural vs urban origin and the number of siblings. No significant interactions with morphometric traits were detected, i.e., within each category of SEP, rural vs urban origin and sex, taller children and those with larger heads and relatively narrower faces were more likely to proceed to secondary and/or tertiary education. The effect of height on education was independent of cranial volume, indicating that taller children did not obtain more educations because their brains were larger than those of shorter children; height per se was important.

Conclusions

Our main finding – that adjusting for other morphometric traits and biosocial variables, morphometric traits still robustly predicted educational attainment, is relevant for understanding the current patterns of evolution of human body size. Our findings suggest that fecundity selection acting on educational attainment could be partly responsible for the concurrent selection for smaller stature and cranial volume in women and opposite trends in men.

Fewer Siblings, More Wealth? Sibship Size and Wealth Attainment

This study examines the association between sibship size and wealth in adulthood. The study draws on resource dilution theory and additionally discusses potentially wealth-enhancing consequences of having siblings. Data from the German Socio-Economic Panel Study (SOEP, N = 3502 individuals) are used to estimate multilevel regression models adjusted for concurrent parental wealth and other important confounders neglected in extant work. The main results of the current study show that additional siblings reduce wealth by about 38%. Parental wealth moderates the association so that sibship size is more negatively associated with filial wealth when parents are wealthier. Birth order position does not moderate the association between sibship size and wealth. The findings suggest that fertility in the family of origin has a systematic impact on wealth attainment and may contribute to population-level wealth inequalities independently from other socio-economic characteristics in families of origin such as parental wealth.

Differences between sons and daughters in the intergenerational transmission of wealth

Persistent interest lies in gender inequality, especially with regard to the favouring of sons over daughters. Economists are concerned with how privilege is transmitted across generations, and anthropologists have long studied sex-biased inheritance norms. There has, however, been no focused cross-cultural investigation of how parent-offspring correlations in wealth vary by offspring sex. We estimate these correlations for 38 wealth measures, including somatic and relational wealth, from 15 populations ranging from hunter-gatherers to small-scale farmers. Although small sample sizes limit our statistical power, we find no evidence of ubiquitous male bias, at least as inferred from comparing parent-son and parent-daughter correlations. Rather we find wide variation in signatures of sex bias, with evidence of both son and daughter-biased transmission. Further, we introduce a model that helps pinpoint the conditions under which simple mid-point parent-offspring wealth correlations can reveal information about sex-biased parental investment. Our findings are relevant to the study of female-biased kinship by revealing just how little normative descriptors of kinship systems, such as patrilineal inheritance, capture intergenerational correlations in wealth, and how variable parent-son and parent-daughter correlations can be. This article is part of the theme issue 'The evolution of female-biased kinship in humans and other mammals'.

Does Living in a Fatherless Household Compromise Educational Success? A Comparative Study of Cognitive and Non-cognitive Skills

This study addresses the relationship between various family forms and the level of cognitive and non-cognitive skills among 15- to 16-year-old students. We measure cognitive skills using standardized scores in mathematics; non-cognitive abilities are captured by a composite measure of internal locus of control related to mathematics. A particular focus lies on father absence although we also examine the role played by co-residence with siblings and grandparents. We use cross-nationally comparable data on students participating in the Programme for International Student Assessment’s release for 2012. By mapping inequalities by family forms across 33 developed countries, this study provides robust cross-country comparable evidence on the relationship of household structure with both cognitive and non-cognitive skills. The study produces three key results: first, the absence of fathers from the household as well as co-residence with grandparents is associated with adverse outcomes for children in virtually all developed countries. Second, this is generally true in terms of both cognitive and non-cognitive skills, although the disadvantage connected to both family forms is notably stronger in the former than in the latter domain. Finally, there is marked cross-national diversity in the effects associated with the presence in the household of siblings and especially grandparents which furthermore differs across the two outcomes considered.

Parental Resources, Sibship Size, and Educational Performance in 20 Countries: Evidence for the Compensation Model

We study whether having several siblings decreases the level of educational performance of adolescents and whether this phenomenon can be compensated by other factors such as the economic or cultural resources of the parents. Based on this compensation model, parental resources should be associated with children's educational attainments more strongly in families with a higher rather than a lower number of children. We analyzed the Program for International Student Assessment (PISA) data from 20 Western countries and found that better family wealth, an increased level of parental education, and a higher parental occupational status were associated with increased educational attainments more strongly among 15-year-old children who have siblings than among children without siblings. The same effect was not found in the case of family cultural possessions. Although parental resources may matter more in larger families than in smaller families, some types of resources are more important than others regarding compensation.

Resource Transfers and Human Life-History Evolution

Formal models of life-history evolution have been used to illuminate both the peculiarities of the human life cycle and its commonalities with those of other taxa. Understanding reproductive decisions in both the contemporary market-based economies of wealthy nation-states and rapidly changing populations largely of the Global South presents particular challenges to evolutionary life-history theory for several reasons. These include (a) the rapidity with which reproductive patterns change, (b) the magnitude of fertility reduction from previous equilibria, and (c) the frequent absence or even reversal of expected wealth-fertility gradients. These empirical challenges have been met to an increasing extent by specifically incorporating durable wealth and resource transfers into more traditional life-history models. Such relatively new models build on classical life-history theory to generate novel predictions. Among these are quite robust predictions that the existence of heritable wealth will decrease optimal fertility and that, once the system of resource transfers is established, fertility and resource transfers will coevolve.

Neuro-cognitive performance of very preterm or very low birth weight adults at 26 years

BACKGROUND

Children born very preterm (VP <32 weeks gestation) and/or with very low birth weight (VBLW <1500 g; subsequently VP/VLBW) have been previously reported to have more cognitive impairment and specific executive functioning problems than term children; however, it remains unclear whether these problems persist into adulthood. This study aimed to examine general intelligence (IQ) and executive functioning (EF) of adults born VP/VLBW in comparison to term controls. Additionally, the effects of smallness for gestational age (SGA) and family socioeconomic status (SES) at birth were investigated.

METHODS

The Bavarian Longitudinal Study is a geographically defined prospective cohort study of neonatal at-risk children born in 1985/86 in Southern Germany. A total of 217 VP/VLBW and 197 controls completed the battery of IQ and EF tests at 26 years of age.

RESULTS

VP/VLBW adults scored significantly lower than controls in IQ and EF. There was a 1.16 standard deviation (SD) unit difference between the VP/VLBW and controls in Full-Scale IQ. VP/VLBW adults were found to have general and multiple cognitive problems rather than specific deficits in EF. SGA was not a significant predictor of cognitive impairment. Family SES had a significant impact on general intelligence in both VP/VLBW and term controls. The SES effects amounted to 1.13 SD units between individuals born into high versus low SES.

CONCLUSIONS

No narrowing of cognitive deficits between VP/VLBW and term control adults to previous childhood assessments at 6 years of age was found. VP/VLBW adults do not outgrow their cognitive problems despite many receiving special educational support in childhood. Low family SES at birth has similar additive adverse effects on cognitive performance in VP/VLBW and term offspring.

Why did children grow so well at hard times? The ultimate importance of pathogen control during puberty

Background and objectives: Secular increase in human height and performance occurred in Europe throughout the 20th century despite the temporally worsening access to nutrients during and after World War II. This pattern is paradoxical under the assumption of the major impact of pre- and postnatal growth conditions for determination of adult size and human capital.

Methodology: We examined the anthropometric parameters of Estonian girls born between 1938 and 1953, and measured around the age of 17 (n = 1475). This period involved two opposite trends in the economic and epidemiological situation: increasing birth-time economic hardships during the war and particularly in the post-war period, and decreasing infant mortality (a proxy of disease burden) after 1947.

Results: Height of girls was negatively affected by the number of siblings and positively by parental socioeconomic position, but these effects were weaker than the secular trend. Leg length (an indicator of pre-pubertal growth conditions) was independent of age and birth date while all other traits, including measures of performance (cranial volume, lung capacity and handgrip strength) showed acceleration. The best predictor of size at age 17 was, in most cases, infant mortality in the year when the girls were aged 11.

Conclusions and implications: Reduction of disease burden during pubertal growth can override effects of resource shortage at birth. Our results also support the idea that increasing efficiency of pathogen control can contribute to the secular increase in cognitive abilities, i.e. the Flynn effect, and that epidemiological transition is the main driver of secular increase in human capital.