Is prematurity associated with adult cognitive outcome and brain structure?

Intergenerational transmission of health inequalities: towards a life course approach to socioeconomic inequalities in health - a review

Adult health inequalities are a persistent public health problem. Explanations are usually sought in behaviours and environments in adulthood, despite evidence on the importance of early life conditions for life course outcomes. We review evidence from a broad range of fields to unravel to what extent, and how, socioeconomic health inequalities are intergenerationally transmitted.We find that transmission of socioeconomic and associated health (dis)advantages from parents to offspring, and its underlying structural determinants, contributes substantially to socioeconomic inequalities in adult health. In the first two decades of life-from conception to early adulthood-parental socioeconomic position (SEP) and parental health strongly influence offspring adult SEP and health. Socioeconomic and health (dis)advantages are largely transmitted through the same broad mechanisms. Socioeconomic inequalities in the fetal environment contribute to inequalities in fetal development and birth outcomes, with lifelong socioeconomic and health consequences. Inequalities in the postnatal environment-especially the psychosocial and learning environment, physical exposures and socialisation-result in inequalities in child and adolescent health, development and behavioural habits, with health and socioeconomic consequences tracking into adulthood. Structural factors shape these mechanisms in a socioeconomically patterned and time-specific and place-specific way, leading to distinct birth-cohort patterns in health inequality.Adult health inequalities are for an important part intergenerationally transmitted. Effective health inequality reduction requires addressing intergenerational transmission of (dis)advantage by creating societal circumstances that allow all children to develop to their full potential.

Long-term effects of prenatal magnesium sulfate exposure on nervous system development in preterm-born children

This study used structural magnetic resonance imaging to analyze changes in the gray matter volume (GMV) of preterm-born (PTB) and term-born (TB) children to help elucidate the influence of magnesium sulfate treatment on the nervous system development. A total of 51 subjects were recruited, including 28 PTB and 23 TB children. The intelligence scale and MRI scan were completed at the corrected age of 10 to 16 years. A whole-brain voxel-wise analysis tested the main effect of the status (PTB without magnesium, PTB with magnesium, and TB) using a factorial design in SPM8. The mean volumes of the regions that showed significant group effects on the GMV after the FDR correction were extracted in the common space for each subject. Verbal and full-scale intelligence quotient scores were significantly lower for PTB children without magnesium than for TB children; however, the scores of PTB children with magnesium and TB children were almost identical. Compared with TB children, PTB children had significantly reduced left straight gyrus and left inferior frontal gyrus GMVs; however, the volumes of PTB children with magnesium were closer to those of TB children. Changes in the GMV of the left inferior frontal gyrus were significantly correlated with full-scale and verbal intelligence quotient scores, whereas the lower gestational age at the time of mgsou4 treatment led to a larger GMV of the left inferior frontal gyrus. Brain structural abnormalities could exist in PTB children. The GMVs of the left straight gyrus and left inferior frontal gyrus were significantly reduced in these children. The influence of magnesium sulfate treatment was not significant, but the cognitive levels of these children were significantly increased and almost identical to those of TB children. Initiation of magnesium sulfate treatment during gestation is negatively correlated with the left inferior frontal gyrus GMV.

Evaluating the effect of birth weight on brain volumes and depression: An observational and genetic study using UK Biobank cohort

Background.

Birth weight influences not only brain development, but also mental health outcomes, including depression, but the underlying mechanism is unclear.

Methods.

The phenotypic data of 12,872–91,009 participants (59.18–63.38% women) from UK Biobank were included to test the associations between the birth weight, depression, and brain volumes through the linear and logistic regression models. As birth weight is highly heritable, the polygenic risk scores (PRSs) of birth weight were calculated from the UK Biobank cohort (154,539 participants, 56.90% women) to estimate the effect of birth weight-related genetic variation on the development of depression and brain volumes. Finally, the mediation analyses of step approach and mediation analysis were used to estimate the role of brain volumes in the association between birth weight and depression. All analyses were conducted sex stratified to assess sex-specific role in the associations.

Result.

We observed associations between birth weight and depression (odds ratio [OR] = 0.968, 95% confidence interval [CI] = 0.957–0.979, p = 2.29 × 10⁻⁶). Positive associations were observed between birth weight and brain volumes, such as gray matter (B = 0.131, p = 3.51 × 10⁻⁷⁴) and white matter (B = 0.129, p = 1.67 × 10⁻⁷⁴). Depression was also associated with brain volume, such as left thalamus (OR = 0.891, 95% CI = 0.850–0.933, p = 4.46 × 10⁻⁵) and right thalamus (OR = 0.884, 95% CI = 0.841–0.928, p = 2.67 × 10⁻⁵). Additionally, significant mediation effects of brain volume were found for the associations between birth weight and depression through steps approach and mediation analysis, such as gray matter (B = –0.220, p = 0.020) and right thalamus (B = –0.207, p = 0.014).

Conclusions.

Our results showed the associations among birth weight, depression, and brain volumes, and the mediation effect of brain volumes also provide evidence for the sex-specific of associations.

A gradient relationship between low birth weight and IQ: A meta-analysis

Multiple studies have reported that individuals with low birth weights (LBW, <2500 g) have a lower intelligence quotient (IQ) than those with normal birth weights (NBW, ≥2500 g). Based on 57 eligible individual studies including 12,137 participants, we performed a meta-analysis to estimate the association between low birth weight and individuals' IQ scores (IQs). The pooled weight mean difference (WMD) in IQs between NBW and LBW individuals was 10 (95% CI 9.26-11.68). The WMD was stable regardless of age. No publication bias was detected. The mean IQs of the extremely low birth weight (ELBW, <1000 g), very low birth weight (VLBW, 1000-1499 g), moderately low birth weight (MLBW, 1500-2499 g) and NBW individuals were 91, 94, 99 and 104, respectively. Additionally, the WMD in IQs with NBW were 14, 10 and 7 for ELBW, VLBW, and MLBW individuals, respectively. Two studies permitted estimates of the influence of social determinants of health to the discrepancy in IQs, which was 13%. Since IQ is inherited and influenced by environmental factors, parental IQs and other factors contribute to residual confounding of the results. As the conclusion was based on population studies, it may not be applicable to a single individual.

Very low birth weight is associated with brain structure abnormalities and cognitive function impairments: A systematic review

Very low birth weight (VLBW) children are at risk of structural brain abnormalities and neurocognitive deficits. Since survival rate of the very low birth weight infants has increased over the past decade, a better understanding of the long-term neurocognitive outcomes is needed. The present systematic review investigated the association between VLBW and cognitive function as well as brain structure. PubMed/Medline, Google Scholar, Scopus and Web of Science databases were searched up from January 2000 to January 2015. The study was restricted to the articles that were about VLBW and its association with cognitive function and brain structure. The initial search yielded 721 articles. There were 44 studies eligible for inclusion after applying the exclusion criteria: 24 follow-up, 14 cohort, and 6 longitudinal studies. Based on this systematic review, we suggest that VLBW is positively related to several cognitive problems and brain structure abnormalities. These findings provide evidence about the importance of early assessment of cognitive development and brain structure to identify at-risk children and provide their specific requirements as early as possible.

Hyper-responsiveness to acute stress, emotional problems and poorer memory in former preterm children

The prevalence of preterm birth (PTB) is high worldwide, especially in developing countries like Brazil. PTB is marked by a stressful environment in intra- as well as extrauterine life, which can affect neurodevelopment and hormonal and physiological systems and lead to long-term negative outcomes. Nevertheless, little is known about PTB and related outcomes later on in childhood. Thus, the goals of the current study were threefold: (1) comparing cortisol and alpha-amylase (sAA) profiles, including cortisol awakening response (CAR), between preterm and full-term children; (2) evaluating whether preterm children are more responsive to acute stress and (3) assessing their memory skills and emotional and behavioral profiles. Basal cortisol and sAA profiles, including CAR of 30 preterm children, aged 6 to 10 years, were evaluated. Further, we assessed memory functions using the Wide Range Assessment of Memory and Learning, and we screened behavior/emotion using the Strengths and Difficulties Questionnaire. The results of preterm children were compared to an age- and sex-matched control group. One week later, participants were exposed to a standardized laboratory stressor [Trier Social Stress Test for Children (TSST-C)], in which cortisol and sAA were measured at baseline, 1, 10 and 25 min after stressor exposure. Preterm children had higher cortisol concentrations at awakening, a flattened CAR and an exaggerated response to TSST-C compared to full-term children. These alterations were more pronounced in girls. In addition, preterm children were characterized by more emotional problems and poorer memory performance. Our findings illustrate the long-lasting and in part sex-dependent effects of PTB on the hypothalamic-pituitary-adrenal (HPA) axis, internalizing behavior and memory. The findings are in line with the idea that early adversity alters the set-point of the HPA axis, thereby creating a more vulnerable phenotype.

Both low birthweight and high birthweight are associated with cognitive impairment in persons with schizophrenia and their first-degree relatives

BACKGROUND

Both low birthweight and high birthweight have been associated with an increased risk for schizophrenia and cognitive impairments in the general population. We assessed the association between birthweight and cognitive performance in persons with schizophrenia and their unaffected first-degree relatives.

METHOD

We investigated a population-based family sample comprising persons with schizophrenia (n = 142) and their unaffected first-degree relatives (n = 277). Both patients and relatives were interviewed with the Structured Clinical Interview for DSM-IV Axis I Disorders, Clinician Version (SCID-CV) and a comprehensive neuropsychological test battery was administered. Information on birthweight was obtained from obstetric records. We used generalized estimating equation (GEE) models to investigate the effect of birthweight, as a continuous variable, on cognitive functioning, adjusting for within-family correlation and relevant covariates.

RESULTS

Both low birthweight and high birthweight were associated with lower performance in visuospatial reasoning, processing speed, set-shifting and verbal and visual working memory among persons with schizophrenia and their unaffected first-degree relatives compared to individuals with birthweight in the intermediate range. The group × birthweight interactions were non-significant.

CONCLUSIONS

Both low birthweight and high birthweight are associated with deficits in cognition later in life. Schizophrenia does not seem to modify the relationship between birthweight and cognition in families with schizophrenia.

Genetic risk for schizophrenia, obstetric complications, and adolescent school outcome: evidence for gene-environment interaction

Low birth weight (LBW) and hypoxia are among the environmental factors most reliably associated with schizophrenia; however, the nature of this relationship is unclear and both gene-environment interaction and gene-environment covariation models have been proposed as explanations. High-risk (HR) designs that explore whether obstetric complications differentially predict outcomes in offspring at low risk (LR) vs HR for schizophrenia, while accounting for differences in rates of maternal risk factors, may shed light on this question. This study used prospectively obtained data to examine relationships between LBW and hypoxia on school outcome at age 15-16 years in a Finnish sample of 1070 offspring at LR for schizophrenia and 373 offspring at HR for schizophrenia, based on parental psychiatric history. Controlling for offspring sex, maternal smoking, social support, parity, age, and number of prenatal care visits, HR offspring performed worse than LR offspring across academic, nonacademic, and physical education domains. LBW predicted poorer academic and physical education performance in HR offspring, but not in LR offspring, and this association was similar for offspring of fathers vs mothers with schizophrenia. Hypoxia predicted poorer physical education score across risk groups. Rates of LBW and hypoxia were similar for LR and HR offspring and for offspring of fathers vs mothers with schizophrenia. Results support the hypothesis that genetic susceptibility to schizophrenia confers augmented vulnerability of the developing brain to the effects of obstetric complications, possibly via epigenetic mechanisms.

Limitations on the developing preterm brain: impact of periventricular white matter lesions on brain connectivity and cognition

Brain lesions to the white matter in peritrigonal regions, periventricular leukomalacia, in children who were born prematurely represent an important model for studying limitations on brain development. The lesional pattern is of early origin and bilateral, that constrains the compensatory potential of the brain. We suggest that (i) topography and severity of periventricular lesions may have a long-term predictive value for cognitive and social capabilities in preterm birth survivors; and (ii) periventricular lesions may impact cognitive and social functions by affecting brain connectivity, and thereby, the dissociable neural networks underpinning these functions. A further pathway to explore is the relationship between cerebral palsy and cognitive outcome. Restrictions caused by motor disability may affect active exploration of surrounding and social participation that may in turn differentially impinge on cognitive development and social cognition. As an outline for future research, we underscore sex differences, as the sex of a preterm newborn may shape the mechanisms by which the developing brain is affected.

An association between both low and high birth weight and increased disorganized and negative symptom severity in schizophrenia and other psychoses

Longitudinal cohort studies have implicated an association between both low and high birth weight and increased schizophrenia risk. In this study, we investigated the effect of birth weight on the symptom severity of psychotic disorders including schizophrenia in a Finnish schizophrenia family study sample. We used a multivariate GEE (General Estimating Equation) regression model to investigate the association of birth weight and symptom severity in 282 subjects with a primary psychotic disorder, 178 of whom had a diagnosis of schizophrenia. The Scales for the Assessment of Positive and Negative Symptoms (SAPS and SANS) were used as a measure of symptom severity. Sex, place of birth and year of birth were adjusted for in the model. Both low and high birth weight were associated with more severe symptoms with respect to bizarre behaviour, affective flattening and attentional impairment. In addition, low birth weight was associated with more severe symptoms with respect to positive formal thought. Our findings suggest that both low and high birth weight can influence the symptom severity of psychotic disorders. Our results implicate an association between both low and high birth weight and disorganized and negative symptoms.

Immune stress in late pregnant rats decreases length of gestation and fecundity, and alters later cognitive and affective behaviour of surviving pre-adolescent offspring

Immune challenge during pregnancy is associated with preterm birth and poor perinatal development. The mechanisms of these effects are not known. 5α-Pregnan-3α-ol-20-one (3α,5α-THP), the neuroactive metabolite of progesterone, is critical for neurodevelopment and stress responses, and can influence cognition and affective behaviours. To develop an immune challenge model of preterm birth, pregnant Long-Evans rat dams were administered lipopolysaccharide [LPS; 30 μg/kg/ml, intraperitoneal (IP)], interleukin-1β (IL-1β; 1 μg/rat, IP) or vehicle (0.9% saline, IP) daily on gestational days 17-21. Compared to control treatment, prenatal LPS or IL-1β reduced gestational length and the number of viable pups born. At 28-30 days of age, male and female offspring of mothers exposed to prenatal IL-1β had reduced cognitive performance in the object recognition task compared to controls. In females, but not males, prenatal IL-1β reduced anxiety-like behaviour, indicated by entries to the centre of an open field. In the hippocampus, progesterone turnover to its 5α-reduced metabolites was lower in prenatally exposed IL-1β female, but not in male offspring. IL-1β-exposed males and females had reduced oestradiol content in hippocampus, medial prefrontal cortex and diencephalon compared to controls. Thus, immune stress during late pregnancy reduced gestational length and negatively impacted birth outcomes, hippocampal function and central neurosteroid formation in the offspring.