Kevin Lewis

November 16, 2010

Mother's educational level and fetal growth: The genesis of health inequalities

Lindsay Silva et al.
International Journal of Epidemiology, October 2010, Pages 1250-1261

Background: Women of low socio-economic status (SES) give birth to lighter babies. It is unknown from which moment during pregnancy socio-economic differences in fetal weight can be observed, whether low SES equally affects different fetal-growth components, or what the effect of low SES is after taking into account mediating factors.

Methods: In 3545 pregnant women participating in the Generation R Study, we studied the association of maternal educational level (high, mid-high, mid-low and low) as a measure of SES with fetal weight, head circumference, abdominal circumference and femur length. We did this before and after adjusting for potential mediators, including maternal height, pre-pregnancy body mass index and smoking.

Results: In fetuses of low-educated women relative to those of high-educated women, fetal growth was slower, leading to a lower fetal weight that was observable from late pregnancy onwards. In these fetuses, growth of the head [-0.16 mm/week; 95% confidence interval (CI): -0.25 to -0.07; P = 0.0004], abdomen (-0.10 mm/week; 95% CI: -0.21 to 0.01; P = 0.08) and femur (-0.03 mm/week; 95% CI: -0.05 to -0.006; P = 0.01) were all slower; from mid-pregnancy onwards, head circumference was smaller, and from late pregnancy onwards, femur length was also smaller. The negative effect of low education was greatest for head circumference (difference in standard deviation score in late pregnancy: -0.26; 95% CI: -0.36 to -0.15; P < 0.0001). This effect persevered even after adjustment for the potential mediators (adjusted difference: -0.14; 95% CI: -0.25 to -0.03; P = 0.01).

Conclusions: Low maternal education is associated with a slower fetal growth and this effect appears stronger for growth of the head than for other body parts.


Light drinking during pregnancy: Still no increased risk for socioemotional difficulties or cognitive deficits at 5 years of age?

Yvonne Kelly, Amanda Sacker, Ron Gray, John Kelly, Dieter Wolke, Jenny Head & Maria Quigley
Journal of Epidemiology and Community Health, forthcoming

Background: This study examines the relationship between light drinking during pregnancy and the risk of socioemotional problems and cognitive deficits at age 5 years.

Methods: Data from the nationally representative prospective UK Millennium Cohort Study (N=11 513) were used. Participants were grouped according to mothers' reported alcohol consumption during pregnancy: never drinker; not in pregnancy; light; moderate; heavy/binge. At age 5 years the strengths and difficulties questionnaire (SDQ) and British ability scales (BAS) tests were administered during home interviews. Defined clinically relevant cut-offs on the SDQ and standardised scores for the BAS subscales were used.

Results: Boys and girls born to light drinkers were less likely to have high total difficulties (for boys 6.6% vs 9.6%, OR=0.67, for girls 4.3% vs 6.2%, OR=0.69) and hyperactivity (for boys 10.1% vs 13.4%, OR=0.73, for girls 5.5% vs 7.6%, OR=0.71) scores compared with those born to mothers in the not-in-pregnancy group. These differences were attenuated on adjustment for confounding and mediating factors. Boys and girls born to light drinkers had higher mean cognitive test scores compared with those born to mothers in the not-in-pregnancy group: for boys, naming vocabulary (58 vs 55), picture similarities (56 vs 55) and pattern construction (52 vs 50), for girls naming vocabulary (58 vs 56) and pattern construction (53 vs 52). Differences remained statistically significant for boys in naming vocabulary and picture similarities.

Conclusions: At age 5 years cohort members born to mothers who drank up to 1-2 drinks per week or per occasion during pregnancy were not at increased risk of clinically relevant behavioural difficulties or cognitive deficits compared with children of mothers in the not-in-pregnancy group.


Causes and Consequences of Early-Life Health

Anne Case & Christina Paxson
Demography, Fall 2010, Pages S65-S85

We examine the consequences of child health for economic and health outcomes in adulthood, using height as a marker of childhood health. After reviewing previous evidence, we present a conceptual framework that highlights data limitations and methodological problems that complicate the study of this topic. We then present estimates of the associations between height and a range of outcomes - including schooling, employment, earnings, health, and cognitive ability - measured in five data sets from early to late adulthood. These results indicate that, on average, taller individuals attain higher levels of education. Height is also positively associated with better economic, health, and cognitive outcomes. These associations are only partially explained by the higher average educational attainment of taller individuals. We then use data from the National Longitudinal Survey of Youth 1979 Children and Young Adults survey to document the associations between health, cognitive development, and growth in childhood. Even among children with the same mother, taller siblings score better on cognitive tests and progress through school more quickly. Part of the differences found between siblings arises from differences in their birth weights and lengths attributable to mother's behaviors while pregnant. Taken together, these results support the hypothesis that childhood health influences health and economic status throughout adulthood.


Challenges to maternal wellbeing during pregnancy impact temperament, attention, and neuromotor responses in the infant rhesus monkey

Christopher Coe, Gabriele Lubach, Heather Crispen, Elizabeth Shirtcliff & Mary Schneider
Developmental Psychobiology, November 2010, Pages 625-637

The relative maturity, alertness, and reactivity of an infant at birth are sensitive indices of the neonate's health, the quality of the pregnancy, and the mother's wellbeing. Even when fetal growth and gestation length have been normal, the maturing fetus can still be adversely impacted by both physical events and psychological challenges to the mother during the prenatal period. The following research evaluated 413 rhesus monkeys from 7 different types of pregnancies to determine which conditions significantly influenced the behavioral responsiveness and state of the young infant. A standardized test battery modeled after the Neonatal Behavioral Assessment Scale for human newborns was employed. The largest impairments in orientation and increases in infant emotional reactivity were seen when female monkeys drank alcohol, even though consumed at only moderate levels during part of the pregnancy. The infants' ability to focus and attend to visual and auditory cues was also affected when the gravid female's adrenal hormones were transiently elevated for 2 weeks by ACTH administration. In addition, responses to tactile and vestibular stimulation were altered by both this ACTH treatment and psychological disturbance during gestation. Conversely, a 2-day course of antenatal corticosteroids 1 month before term resulted in infants with lower motor activity and reactivity. These findings highlight several pregnancy conditions that can affect a young infant's neurobehavioral status, even when otherwise healthy, and demonstrate that alterations or deficits are specific to the type of insult experienced by the mother and fetus.


Genetic Influences on Being Processed Through the Criminal Justice System: Results from a Sample of Adoptees

Kevin Beaver
Biological Psychiatry, forthcoming

Background: Behavioral genetic research has revealed that antisocial phenotypes are under genetic influence. This study examines whether genetic factors also affect the odds of being processed through the criminal justice system.

Methods: A sample of adoptees (n = 191-257) drawn from the National Longitudinal Study of Adolescent Health was analyzed. They self-reported on whether they had ever been arrested, sentenced to probation, incarcerated, and arrested multiple times. Assessments were also conducted of the criminal status of their biological parents.

Results: Adoptees who have a biological father or a biological mother who have been arrested previously are significantly more likely to be arrested, sentenced to probation, incarcerated, and arrested multiple times when compared with adoptees whose biological parents have not been arrested.

Conclusions: Adoptees who are genetically predisposed to antisocial phenotypes are at risk for being formally processed through the criminal justice system.


The Benefits of Breastfeeding Across the Early Years of Childhood

Clive Belfield & Inas Rashad Kelly
NBER Working Paper, October 2010

The choice to breastfeed rather than formula-feed an infant as well as the duration of doing so has been scrutinized in more recent times. Yet, key identification issues remain to be resolved, including the array of possible child development benefits, the optimal intensity of breastfeeding versus formula- feeding, and the possibility of confounding with other inputs that promote child health. This study uses the Early Childhood Longitudinal Survey - Birth Cohort to explore the causal effect of breastfeeding on development across the early years of childhood. We examine a range of health, physical, and cognitive outcomes and relate these to a set of breastfeeding and formula-feeding intensities. Adjusting for a very extensive set of potential confounding factors that also promote child development, our empirical method uses simultaneous equations models and propensity score measures to understand the link between breastfeeding and child outcomes. Our results indicate that breastfeeding and not formula-feeding at birth are associated with increased probabilities of being in excellent health at 9 months. Furthermore, they are protective against obesity and improve cognitive outcomes at 24 months and 54 months. Breastfeeding for 6 months or more increases motor scores at 9 months.


Understanding the Early Origins of the Education-Health Gradient: A Framework That Can Also Be Applied to Analyze Gene-Environment Interactions

Gabriella Conti & James Heckman
Perspectives on Psychological Science, September 2010, Pages 585-605

In this article, we develop a framework for analyzing the causal effects of interventions in the presence of latent factors that could affect outcomes, even in the absence of interventions. This framework will be useful in situations in which genes are included among the latent factors. We estimate the model and study the early origins of observed later-life disparities by education. We determine the role played by cognitive, noncognitive, and early health endowments. We identify the causal effect of education on health and health-related behaviors. We show that family background characteristics and cognitive, noncognitive, and health endowments developed by age 10 are important determinants of health disparities at age 30. We also show that not properly accounting for personality traits results in overestimation of the importance of cognitive ability in determining later health. Selection on preexisting traits explains more than half of the observed differences in poor health and obesity. Education has an important causal effect in explaining differences in smoking rates. There are significant gender differences. We go beyond the current literature, which typically estimates mean effects, to compute distributions of treatment effects. We show that the effect of education on health varies among individuals who are similar in their observed characteristics, and how a mean effect can hide gains and losses for different individuals. This analysis highlights the crucial role played by promotion of good health at an early age and the importance of prevention in the reduction of health disparities. We speculate about how the model can be applied to genetic studies.


Maternal work early in the lives of children and its distal associations with achievement and behavior problems: A meta-analysis

Rachel Lucas-Thompson, Wendy Goldberg & JoAnn Prause
Psychological Bulletin, November 2010, Pages 915-942

This meta-analysis of 69 studies (1,483 effect sizes) used random effects models to examine maternal employment during infancy/early childhood in relation to 2 major domains of child functioning: achievement and behavior problems. Analyses of studies that spanned 5 decades indicated that, with a few exceptions, early employment was not significantly associated with later achievement or internalizing/externalizing behaviors. The exceptions were for teacher ratings of achievement and internalizing behaviors: Employment was associated with higher achievement and fewer internalizing behaviors. Substantial heterogeneity among the effect sizes prompted examination of moderators. Sample-level moderator analyses pointed to the importance of socioeconomic and contextual variables, with early employment most beneficial when families were challenged by single parenthood or welfare status. Maternal employment during Years 2 and 3 was associated with higher achievement. Some moderator analyses indicated negative effects of employment for middle-class and 2-parent families and for very early employment (child's first year). Associations also differed depending on whether effect sizes were adjusted for contextual variables. Only 1 study-level moderator (sex of first author) was significant after adjusting for other moderators. The small effect size and primarily nonsignificant results for main effects of early maternal employment should allay concerns about mothers working when children are young. However, negative findings associated with employment during the child's first year are compatible with calls for more generous maternal leave policies. Results highlight the importance of social context for identifying under which conditions and for which subgroups early maternal employment is associated with positive or negative child outcomes.


Maternal Life Satisfaction and Child Outcomes: Are They Related?

Eva Berger & Katharina Spiess
Journal of Economic Psychology, forthcoming

This paper investigates the association between maternal life satisfaction and the developmental functioning of two- to three-year-old children as well as the socio-emotional behavior of five- to six-year-old children. We use data from the German Socio-Economic Panel Study (SOEP), which allows us to control for a rich set of child and parental characteristics and to use the mother's life satisfaction before the birth of her child as an instrument to eliminate potential reverse causality. The results indicate that the more satisfied the mother, the better her child's verbal skills and the lower his or her socio-emotional problems. The relation is more pronounced for boys than for girls. The results are robust even when mothers' personality or mothers' cognitive skills are controlled for.


Digit ratio, nicotine and alcohol intake and national rates of smoking and alcohol consumption

John Manning & Bernhard Fink
Personality and Individual Differences, forthcoming

The intake of nicotine (mainly through smoking) and alcohol has public health consequences. However, it is unclear whether all factors that affect individual and national rates of consumption are known. Prenatal testosterone (PT) may influence smoking and alcohol choices through effects on personality. Thus, morphological markers of PT may correlate with smoking and/or alcohol intake choices. Here we examine the relationship between individual values and national means of 2D:4D, a putative negative correlate of PT, and intake of nicotine and alcohol in a large sample of men and women, i.e. the BBC Internet Study. High intake of nicotine was related to high 2D:4D and high intake of alcohol with low 2D:4D. These findings were independent of sex, age, height, education, and individual choices regarding nicotine or alcohol intake. National means of 2D:4D were positively correlated with number of cigarettes consumed per nation after the removal of the effects of gross domestic product (GDP), average height and consumption of alcohol. Alcohol consumption correlated negatively with national 2D:4D after the influence of GDP, average height and consumption of cigarettes per nation were removed. We conclude that PT may have organising effects on smoking and alcohol intake choices.


Acute Prenatal Exposure To Ethanol And Social Behavior: Effect Of Age, Sex, And Timing Of Exposure

Sandra Mooney & Elena Varlinskaya
Behavioural Brain Research, 1 January 2011, Pages 358-364

During development of the central nervous system, neurons pass through critical periods of vulnerability to environmental factors. Exposure to ethanol during gastrulation or during neuronal generation results in a permanent reduction in the number of neurons in trigeminal-associated cranial nerve nuclei. Normal functioning of the trigeminal system is required for social behavior, the present study examined the effects of acute prenatal exposure to ethanol on social interactions across ontogeny. Pregnant Long-Evans rats were injected with 2.9 g/kg ethanol (i.p., 20% v/v solution; peak blood ethanol concentrations of 300 mg/dl) or an equivalent volume of saline on gestational day (G) 7 (gastrulation) or G12 (neuronal generation). Subsequently, social investigation, play fighting, contact behavior, social motivation, and overall locomotor activity in the social context were assessed in male and female offspring during early adolescence, late adolescence, or adulthood, on postnatal day (P) 28, P42, or P75, respectively, using a modified social interaction test. Ethanol exposure on G7 resulted in mild changes of social behavior evident in young adolescents only. In contrast, animals exposed to ethanol on G12 demonstrated pronounced behavioral deficits throughout ontogeny, with deficits being most robust in male offspring. Males exposed to ethanol on G12 showed decreases in social investigation, contact behavior, and play fighting, whereas a decrease in social motivation, i.e., transformation of social preference into social avoidance, was evident at P42 and P75 regardless of sex. These findings show that acute exposure to ethanol alters social behavior, and that the timing of the exposure defines the behavioral outcome.


Memory and brain volume in adults prenatally exposed to alcohol

Claire Coles et al.
Brain and Cognition, forthcoming

The impact of prenatal alcohol exposure on memory and brain development was investigated in 92 African-American, young adults who were first identified in the prenatal period. Three groups (Control, n = 26; Alcohol-related Neurodevelopmental Disorder, n = 36; and Dysmorphic, n = 30) were imaged using structural MRI with brain volume calculated for multiple regions of interest. Memory was measured using the Verbal Selective Reminding Memory Test and its nonverbal counterpart, the Nonverbal Selective Reminding Memory Test, which each yielding measures of learning and recall. For both Verbal and Nonverbal Recall and Slope, linear trends were observed demonstrating a spectrum of deficits associated with prenatal alcohol exposure. Dysmorphic individuals performed significantly poorer than unexposed controls on 5 of 6 memory outcomes. Alcohol-exposed individuals demonstrated significantly lower total brain volume than controls, as well as lower volume in a number of specific regions including hippocampus. Mediation analyses indicated that memory performance associated with effects of prenatal alcohol exposure was mediated from dysmorphic severity through hippocampal volume, particularly right hippocampus. These results indicate that the association between the physical effects of prenatal alcohol exposure and deficits in memory are mediated by volumetric reduction in specific brain regions.


Maternal prenatal licorice consumption alters hypothalamic-pituitary-adrenocortical axis function in children

Katri Räikkönen et al.
Psychoneuroendocrinology, November 2010, Pages 1587-1593

Overexposure to glucocorticoids has been proposed as a mechanism by which prenatal adversity ‘programs' the function of the hypothalamic-pituitary-adrenocortical axis (HPAA), thereby increasing the risk of adult diseases. Glycyrrhizin, a natural constituent of licorice, potently inhibits 11β-hydroxysteroid dehydrogenase type 2, the feto-placental barrier to the higher maternal cortisol levels. We studied if maternal consumption of glycyrrhizin in licorice associates with HPAA function in children. Diurnal salivary cortisol and salivary cortisol during the Trier Social Stress Test for Children (TSST-C) were measured in children (n = 321, mean age = 8.1, SD = 0.3 years) whose mothers consumed varying levels of glycyrrhizin in licorice during pregnancy; exposure-level groups were labeled high (≥500 mg/week), moderate (250-499 mg/week) and zero-low (0-249 mg/week). In comparison to the zero-low exposure group, children in the high exposure group had 19.2% higher salivary cortisol awakening peak, 33.1% higher salivary cortisol awakening slope, 15.4% higher salivary cortisol awakening area under the curve (AUC), 30.8% higher baseline TSST-C salivary cortisol levels, and their salivary cortisol levels remained high throughout the TSST-C protocol (P-values <0.05). These effects appeared dose-related. Our findings lend support to prenatal ‘programming' of HPAA function by overexposure to glucocorticoids.


Breastfeeding and later psychosocial development in the Philippines

Paulita Duazo, Josephine Avila & Christopher Kuzawa
American Journal of Human Biology, November/December 2010, Pages 725-730

Objectives: Evaluate whether breastfeeding (BF) duration predicts later psychosocial development (PD) in a large low socioeconomic status (SES) sample in the Philippines.

Methods: The sample consists of 2,752 children aged 5-6 years who were measured in 2004 as part of the Philippine government's Early Childhood Development Project. Duration of any BF was the primary independent variable in regression models predicting a cumulative index of PD that has been shown previously to predict school readiness.

Results: In this sample, mothers who breastfed their children for longer tended to have lower educational attainment and to come from lower income households. Despite this, BF duration was a positive predictor of future PD measured in late childhood, but only after adjustment for SES and related confounders.

Conclusions: These findings add to growing evidence that BF could provide lasting economic and social benefits and underscore the importance of continuing current public health efforts to promote BF in the Philippines and across the globe.


Genetic liability, environment, and the development of fussiness in toddlers: The roles of maternal depression and parental responsiveness

Misaki Natsuaki et al.
Developmental Psychology, September 2010, Pages 1147-1158

Using a longitudinal, prospective adoption design, the authors of this study examined the effects of the environment (adoptive parents' depressive symptoms and responsiveness) and genetic liability of maternal depression (inferred by birth mothers' major depressive disorder [MDD]) on the development of fussiness in adopted children between 9 and 18 months old. The sample included 281 families linked through adoption, with each family including 4 individuals (i.e., adopted child, birth mother, adoptive father and mother). Results showed that adoptive mothers' depressive symptoms when their child was 9 months old were positively associated with child fussiness at 18 months. A significant interaction between birth mothers' MDD and adoptive mothers' responsiveness indicated that children of birth mothers with MDD showed higher levels of fussiness at 18 months when adoptive mothers had been less responsive to the children at 9 months. However, in the context of high levels of adoptive mothers' responsiveness, children of birth mothers with MDD did not show elevated fussiness at 18 months. Findings are discussed in terms of gene-environment interactions in the intergenerational risk transmission of depression.


Genetic Interactions with Prenatal Social Environment: Effects on Academic and Behavioral Outcomes

Dalton Conley & Emily Rauscher
NBER Working Paper, May 2010

Caspi et al. (2002, 2003), Guo et al. (2008a), and Pescosolido et al. (2008) all claim to have demonstrated allele-by-environment interactions, but in all cases environmental influences are potentially endogenous to the unmeasured genetic characteristics of the subjects and their families. Thus, gene-gene interactions cannot be ruled out as an alternative explanation. Second, these studies have not deployed adjustments for multiple hypothesis testing-always an issue, but particularly so for GE studies with multiple alleles and outcomes. Using data from the National Longitudinal Survey of Adolescent Health (Add Health), we address these limitations of previous studies by taking advantage of a natural experiment that randomizes a particular environmental influence - fetal position, resulting in birth weight discordance within monozygotic twin pairs (validated with dizygotic twins as well). Whether or not we use corrections for multiple statistical tests, we find no support for the GE interactions (or for main effects of genes or birth weight) found in past research and, in fact, the only significant allele-birth weight interaction we reveal works in the opposite direction of Caspi et al.'s classic finding on 5-HTT and maltreatment.


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