Intellectual Disability in a Birth Cohort: Prevalence, Etiology, and Determinants at the Age of 4 Years

The research landscape concerning environmental factors in neurodevelopmental disorders: Endocrine disrupters and pesticides-A review

In recent years, environmental epidemiology and toxicology have seen a growing interest in the environmental factors that contribute to the increased prevalence of neurodevelopmental disorders, with the purpose of establishing appropriate prevention strategies. A literature review was performed, and 192 articles covering the topic of endocrine disruptors and neurodevelopmental disorders were found, focusing on polychlorinated biphenyls, polybrominated diphenyl ethers, bisphenol A, and pesticides. This study contributes to analyzing their effect on the molecular mechanism in maternal and infant thyroid function, essential for infant neurodevelopment, and whose alteration has been associated with various neurodevelopmental disorders. The results provide scientific evidence of the association that exists between the environmental neurotoxins and various neurodevelopmental disorders. In addition, other possible molecular mechanisms by which pesticides and endocrine disruptors may be associated with neurodevelopmental disorders are being discussed.

PM2.5 threshold exceedances during the prenatal period and risk of intellectual disability

BACKGROUND

Research demonstrates that chronic exposure to fine particulates (PM2.5) increases risks of neurodevelopmental conditions, such as intellectual disability (ID). Few studies have examined neurodevelopmental health impacts of pollution spikes exceeding 24-h (24-h) PM2.5 guidelines, despite relevance to the regulatory landscape. The current potential for regulatory changes to 24-h PM2.5 standards in the United States makes research on exceedances relevant.

OBJECTIVE

To examine associations between 24-h PM2.5 exceedances and the risk of ID.

METHODS

We conducted a retrospective case-control study of a sample of children in Utah, USA. We used generalized estimating equations to predict odds of ID based on the number of 24-h PM2.5 exceedance days during the preconception period and three trimesters of pregnancy. Exceedance days are defined as per current World Health Organization (WHO) [≥15 μg/m3] and current US Environmental Protection Agency (EPA) [≥35 μg/m3] 24-h guidelines.

RESULTS

PM2.5 exceedances are associated with ID risk during the preconception and first trimester periods and not the second and third trimesters. During the preconception period, each day exceeding 15 μg/m3 or 35 μg/m3 was associated with a 1.023 (CI: 1.011-1.040) or 1.042 (CI: 1.026-1.059, p < 0.001) increase in odds of ID, respectively. During the first trimester, each day exceeding 15 μg/m3 or 35 μg/m3 was associated with a 1.032 (CI: 1.017-1.047) or 1.059 (CI: 1.030-1.088) increase in odds of ID, respectively.

IMPACT STATEMENT

Potential regulatory movement on the US 24-h PM2.5 standard makes research that explicitly studies exceedances highly relevant. Yet few studies examine health effects of exceeding 24-h guidelines for any air pollutants. This study fills important gaps in the literature by examining associations between odds of intellectual disability and the count of days exceeding current 24-h PM2.5 guidelines, as established by the World Health Organization and US Environmental Protection Agency, during the prenatal period. We find that exceedances of both sets of guidelines, during the preconception and first trimester periods, are associated with ID risk.

Comparative Transcriptomics Data Profiling Reveals E2F Targets as an Important Biological Pathway Overexpressed in Intellectual Disability Disorder

Intellectual disability (ID) is an early childhood neurodevelopmental disorder that is characterized by impaired intellectual functioning and adaptive behavior. It is one of the major concerns in the field of neurodevelopmental disorders across the globe. Diversified approaches have been put forward to overcome this problem. Among all these approaches, high throughput transcriptomic analysis has taken an important dimension. The identification of genes causing ID rapidly increased over the past 3 to 5 years owing to the use of sophisticated high throughput sequencing platforms. Early monitoring and preventions are much important for such disorder as their progression occurs during fetal development. This study is an attempt to identify differentially expressed genes (DEGs) and upregulated biological processes involved in development of ID patients through comparative analysis of available transcriptomics data. A total of 7 transcriptomic studies were retrieved from National Center for Biotechnology Information (NCBI) and were subjected to quality check and trimming prior to alignment. The normalization and differential expression analysis were carried out using DESeq2 and EdgeR packages of Rstudio to identify DEGs in ID. In progression of the study, functional enrichment analysis of the results obtained from both DESeq2 and EdgeR was done using gene set enrichment analysis (GSEA) tool to identify major upregulated biological processes involved in ID. Our findings concluded that monitoring the level of E2F targets, estrogen, and genes related to oxidative phosphorylation, DNA repair, and glycolysis during the developmental stage of an individual can help in the early detection of ID disorder.

Alarming changes in the global burden of mental disorders in children and adolescents from 1990 to 2019: a systematic analysis for the Global Burden of Disease study

Mental disorders account for a large and increasing health burden worldwide, as shown in the Global Burden of Diseases (GBD) Study 2010. Unpacking how this burden in children and adolescents varies with sex, geographical regions, and ethnicities and how it has changed in the last 3 decades are important to improve the existing public health policies and prevention strategies. The study was conducted using GBD 2019 database. The burden of children and adolescents' (< 20 years old) mental disorders was displayed as prevalence, incidence, disability-adjusted life-years (DALYs), years of life lost, and years lived with disability globally between 1990 and 2019. The number of DALYs in children and adolescents diagnosed with mental disorders was 21.5 million (95% CI: 15.2-29.6 million) in 2019. From 1990 to 2019, the age-standardized rates of DALYs of mental disorders increased from 803.8 per 100,000 (95% CI: 567.7-1104.3 per 100,000) to 833.2 per 100,000 (95% CI: 589.0-1146.1 per 100,000) population. Over the past 30 years, there had been a huge increase in the number of individuals suffering from anxiety disorders, major depressive disorders, and conduct disorders including an alarming increase in the rate of eating disorders such as 24.3% in bulimia nervosa and 17.0% in anorexia nervosa. Globally, 8.8% of children and adolescents have been diagnosed with varieties of mental illnesses, accounting for a heavy disease burden on public health. Besides, the worldwide increasing rates of anxiety disorders, major depressive disorders, and eating disorders have brought considerable challenges to public health undertakings, for which further prevention and treatment countermeasures are urgently needed.

Associations between estimates of perinatal industrial pollution exposures and intellectual disability in Utah children

While heavy metals exposure is associated with intellectual disability (ID), little is known about associations between industrial pollution and ID. The objective of this analysis is to assess associations between estimated perinatal industrial pollution exposures from the US Environmental Protection Agency's Risk Screening Environmental Indicators Microdata and children's ID risk. We conducted a case-control study of children born in Utah from 2000 to 2008 (n = 1679). Cases were identified through the Center for Disease Control's Autism and Developmental Disabilities Monitoring Network's Utah site and matched with controls based on birth year, sex, and birth county. We used multivariable generalized estimating equations to examine associations between estimated perinatal industrial pollution exposures and ID risk. The fourth quartile of industrial pollution exposure was associated with increased odds of ID relative to the first (Odds Ratio [OR]: 1.73, 95% Confidence Interval [CI]: 1.23-2.44) and second (OR: 1.67, CI: 1.19-2.35) quartiles. Similarly, the third quartile was associated with increased odds of ID relative to the first (OR: 1.47, CI: 1.06-2.03) and second (OR: 1.41, CI: 1.02-1.96) quartiles. Findings were robust to varied model specifications. Maternal residential exposures to industrial pollution were associated with increased ID prevalence in Utah. Since environmental correlates of ID are understudied, additional research is needed.

Choices, challenges, and constraints: a pragmatic examination of the limits of mental age matching in empirical research

The work of Ed Zigler spans decades of research all singularly dedicated to using science to improve the lives of children facing different challenges. The focus of this article is on one of Zigler's numerous lines of work: advocating for the practice of mental age (MA) matching in empirical research, wherein groups of individuals are matched on the basis of developmental level, rather than chronological age. While MA matching practices represented a paradigm shift that provided the seeds from which the developmental approach to developmental disability sprouted, it is not without its own limits. Here, we examine and test the underlying assumption of linearity inherent in MA matching using three commonly used IQ measures. Results provide practical constraints of using MA matching, a solution which we hope refines future clinical and empirical practices, furthering Zigler's legacy of continued commitment to compassionate, meaningful, and rigorous science in the service of children.

The mechanism of enriched environment repairing the learning and memory impairment in offspring of prenatal stress by regulating the expression of activity-regulated cytoskeletal-associated and insulin-like growth factor-2 in hippocampus

Background

Prenatal stress can cause neurobiological and behavioral defects in offspring; environmental factors play a crucial role in regulating the development of brain and behavioral; this study was designed to test and verify whether an enriched environment can repair learning and memory impairment in offspring rats induced by prenatal stress and to explore its mechanism involving the expression of insulin-like growth factor-2 (IGF-2) and activity-regulated cytoskeletal-associated protein (Arc) in the hippocampus of the offspring.

Methods

Rats were selected to establish a chronic unpredictable mild stress (CUMS) model during pregnancy. Offspring were weaned on 21st day and housed under either standard or an enriched environment. The learning and memory ability were tested using Morris water maze and Y-maze. The expression of IGF-2 and Arc mRNA and protein were respectively measured by using RT-PCR and Western blotting.

Results

There was an elevation in the plasma corticosterone level of rat model of maternal chronic stress during pregnancy. Maternal stress’s offspring exposed to an enriched environment could decrease their plasma corticosterone level and improve their weight. The offspring of maternal stress during pregnancy exhibited abnormalities in Morris water maze and Y-maze, which were improved in an enriched environment. The expression of IGF-2, Arc mRNA, and protein in offspring of maternal stress during pregnancy was boosted and some relationships existed between these parameters after being exposed enriched environment.

Conclusions

The learning and memory impairment in offspring of prenatal stress can be rectified by the enriched environment, the mechanism of which is related to the decreasing plasma corticosterone and increasing hippocampal IGF-2 and Arc of offspring rats following maternal chronic stress during pregnancy.

Vestibular function in adults with intellectual disabilities: feasibility and outcome of a vestibular screening protocol in Special Olympics athletes

OBJECTIVE

This study aimed to evaluate the feasibility of a well-adapted vestibular screening battery to objectively examine the (peripheral) vestibular function, and to explore the characteristics of potential vestibular deficits in the adult ID population.

DESIGN

Cross-sectional study design.

STUDY SAMPLE

Compared to an age- and gender-weighted control group, a heterogeneous group of forty-five adults with ID participated in the vestibular screening at the National Games of Special Olympics Belgium (2019), which consisted of a bone conduction cervical Vestibular Evoked Myogenic Potential (cVEMP) measurement and video Head Impulse Test (vHIT).

RESULTS

The screening battery appeared to be feasible in the majority of the participants (cVEMP: 92%; vHIT: 72%). Overall, the occurrence of abnormal cVEMP and vHIT responses was significantly higher in the ID group, with significantly lower corrected peak-to-peak cVEMP amplitudes (p < 0.001), lower vHIT gains (p < 0.001), and higher cVEMP and vHIT asymmetry ratios in the ID group (p = 0.008 and p < 0.001 resp.).

CONCLUSIONS

Vestibular assessment using the cVEMP and vHIT technique shows a promising feasibility in adults with ID. In addition, this study suggests that people with ID exhibit an increased prevalence of (peripheral) vestibular deficits relative to the general population.

The diagnostic yield of intellectual disability: combined whole genome low-coverage sequencing and medical exome sequencing

Background

Intellectual disability (ID) is a heterogeneous neurodevelopmental disorder with a complex genetic underpinning in its etiology. Chromosome microarray (CMA) is recommended as the first-tier diagnostic test for ID due to high detection rate of copy number variation (CNV).

Methods

To identify an appropriate clinical detection scheme for ID in Han Chinese patients, whole genome low-coverage sequencing was performed as the first-tier diagnostic test, and medical exome sequencing (MES) as the second-tier diagnostic test for patients with negative results of CNVs.

Results

A total of 19 pathogenic CNVs in 16/95(16.84%) ID patients and 10 pathogenic single-nucleotide variations (SNVs), including 6 novel mutations in 8/95(8.42%) ID patients were identified on whom no pathogenic CNVs were discovered. The detection rate of CNVs in ID with multiple congenital anomalies (MCA) subgroup was significantly higher than ID with autism spectrum disorders and other IDs subgroups. And the single-nucleotide variations showed a higher occurrence rate in the other IDs subgroup.

Conclusions

There were differences in the diagnostic yields of different variation types among the three ID subgroups. Our findings provided a new perspective on appropriate clinical detection scheme in different ID subgroups based on statistically significant differences among the three ID subgroups. The application of whole genome low-coverage sequencing as the first-tier diagnostic test for ID with MCA subgroup and MES as the first-tier diagnostic test for other ID subgroup was considered as an efficient clinical detection scheme.

Exome Sequencing in Children

BACKGROUND

In developed countries, global developmental disorders are encounter- ed in approximately 1% of all children. The causes are manifold, and no exogenous cause can be identified in about half of the affected children. The parallel investi- gation of the coding sequences of all genes of the affected individual (whole exome sequencing, WES) has developed into a successful diagnostic method for identify- ing the cause of the problem. It is not yet clear, however, when WES should best be used in routine clinical practice in order to exploit the potential of this method to the fullest.

METHODS

In an interdisciplinary study, we carried out standardized clinical pheno- typing and a systematic genetic analysis (WES of the index patient and his or her parents, so-called trio WES) in 50 children with developmental disturbances of unclear etiology and with nonspecific neurological manifestations.

RESULTS

In 21 children (42% of the collective), we were able to identify the cause of the disorder by demonstrating a mutation in a gene known to be associated with disease. Three of these children subsequently underwent specific treatment. In 22 other children (44%), we detected possibly etiological changes in candidate genes not currently known to be associated with human disease.

CONCLUSION

Our detection rate of at least 42% is high in comparison with the results obtained in other studies from Germany and other countries to date and implies that WES can be used to good effect as a differential diagnostic tool in pediatric neurol- ogy. WES should be carried out in both the index patient and his or her parents (trio- WES) and accompanied by close interdisciplinary collaboration of human geneti- cists and pediatricians, by comprehensive and targeted phenotyping (also after the diagnosis is established), and by the meticulous evaluation of all gene variants.

Development of tablet personal computer-based cognitive training programs for children with developmental disabilities whose cognitive age is less than 4 years

This study was to develop tablet personal computer-based cognitive training programs for children with developmental disabilities whose cognitive age is less than 4 years. Twelve cognitive training programs (named Injini) were designed comprising cognitive domains that included attention, visual and auditory perception, memory, executive function, language, and reasoning. In addition, programs related to learning experiences, such as self-regulation, role play, learning of number, and letter/shape concepts, comparison, classification, and pattern matching, were included. Six of 12 programs comprised approximately 10 levels for each program, with different difficulty levels. Other programs consisted of universal tasks that did not have a difficulty level. To ensure that the difficulty level was appropriate, we pre-tested the pilot version of Injini among 80 children with typical development aged 18 to 41 months. After modifying the pilot version, we developed the final version and tested it among 80 children with cognitive impairment whose cognitive age was 18 to 41 months. All children were assessed using the Bayley Scales of Infant and Toddler Development to determine their development and cognitive age. The difficulty level analyses in children with typical development revealed several inappropriate results wherein the success rate did not decrease with increase in level in some programs. After adjusting the difficulty level, the analyses in children with cognitive impairment demonstrated that the success rate gradually decreased with increasing level in all programs. Cognitive training programs for children with developmental disabilities were successfully developed.

Pre and postnatal characteristics of children and adolescents with intellectual disability

ABSTRACT Purpose: to describe pre and postnatal characteristics of children and adolescents with intellectual disability. Methods: study performed with all individuals who received healthcare between August 2016 and February 2018 at a reference Rehabilitation Center which serves 27 towns and cities in the South of Santa Catarina State, Brazil. A questionnaire focusing on demographic, socioeconomic, pre and postnatal variables was administered to parents or guardians of children and adolescents by trained interviewers. Descriptive analyses were performed using absolute and relative frequencies of categorical variables and central tendency and dispersion measures of numerical variables. Results: 42 individuals in the mean age of 11 years (± 3.0) were studied. Most mothers reported having unintended pregnancy and more than a half reported having had a cesarean section. In addition, about one-fifth of the subjects had low birth weight and most of them received exclusive breastfeeding up to six months of age. Conclusion: these findings are crucial for the organization and improvement of health care services, since they provide evidence for health professionals to improve and/or focus their health care initiatives on these individuals.

Risk Factors Associated with Severity of Nongenetic Intellectual Disability (Mental Retardation) among Children Aged 2-18 Years Attending Kenyatta National Hospital

Background

Many of the nongenetic causal risk factors of intellectual disability (ID) can be prevented if they are identified early. There is paucity on information regarding potential risk factors associated with this condition in Kenya. This study aimed to establish risk factors associated with severity of nongenetic intellectual disability (ID) among children presenting with this condition at Kenyatta National Hospital (KNH).

Methods

A hospital-based cross-sectional study was conducted over the period between March and June 2017 in pediatric and child/youth mental health departments of Kenyatta National Hospital (KNH), Kenya. It included children aged 2–18 years diagnosed with ID without underlying known genetic cause.

Results

Of 97 patients with nongenetic ID, 24% had mild ID, 40% moderate, 23% severe-profound, and 10% unspecified ID. The mean age of children was 5.6 (±3.6) years. Male children were predominant (62%). Three independent factors including “labor complications” [AOR = 9.45, 95% CI = 1.23–113.29, P = 0.036], “admission to neonatal intensive care unit” [AOR = 8.09, 95% CI = 2.11–31.07, P = 0.002], and “cerebral palsy” [AOR = 21.18, CI = 4.18–107.40, P ≤ 0.001] were significantly associated with increased risk of severe/profound nongenetic ID.

Conclusion

The present study findings suggest that perinatal complications as well as postnatal insults are associated with increased risk of developing severe-profound intellectual disability, implying that this occurrence may be reduced with appropriate antenatal, perinatal, and neonatal healthcare interventions.

Integrated children's clinic care (ICCC) versus a self-directed care pathway for children with a chronic health condition: a multi-centre randomised controlled trial study protocol

Background

Children with chronic health conditions have better health-related outcomes when their care is managed in a personalised and coordinated way. However, increased demand on Australian ambulatory care hospital services has led to longer waitlist times to access specialists and appropriate intervention services; placing vulnerable children at increased risk of poorer short-term (e.g. social difficulties) and long-term (e.g. convictions) health and social outcomes. Traditional approaches to increasing frequency and service of delivery are expensive and can have minimal impact on caregiver burden. A community based service-integration approach, rather than self-directed care is proposed as increased service linkages are more likely to occur and improve the health outcomes of children with a chronic health condition.

Methods

An open, unblinded, multi-centre randomised controlled trial in two Australian public hospitals. 112 children (0–16 years) fulfilling the inclusion criteria will be randomised to one of two clinical pathways for management of their chronic health condition: (1) integrated children’s care clinic (ICCC) or (2) self-directed care pathway. All children and caregivers will be interviewed at 1 week, and 3, 6 and 12 month time intervals. Primary outcome measures include the Pediatric Quality of Life (PedQOL) questionnaire, Subjective Units of Distress Scale, Child Behaviour Checklist (CBCL) and Rotter’s Locus of Control Scale. Secondary outcome measures include the total number of medical appointments, school days missed and quantity of services accessed. Our main objectives are to determine if the ICCC results in better health and economics outcomes compared to the self-directed care pathway.

Discussion

The success of a health systems approach needs to be balanced against clinical, mortality and cost-effectiveness data for long-term sustainability within a publicly funded health system. A clinical pathway that is sustainable, cost-effective, provides efficient evidence-based care and improves the quality of life outcomes for children with chronic health conditions has the potential to reduce waitlist times, improve access to health services, increase consumer satisfaction; and prevent costs associated with poorly managed chronic health conditions into adulthood. This study will be the first to provide clinical and health economics data on an integrated care pathway for the management of chronic health conditions in children. On a broader scale, results from this study will help guide care coordination frameworks for children with chronic health conditions; particularly with the introduction and implementation of a National Disability Insurance Scheme (NDIS) across Australia.

Trial registration

Australia and New Zealand Clinical Trials Register (ANZCTR) ACTRN12617001188325. Registered: 14th August, 2017.

Electronic supplementary material

The online version of this article (10.1186/s12887-018-1034-x) contains supplementary material, which is available to authorized users.