Epidemiology of mental retardation in children

Age- and Gender-Specific Prevalence of Intellectually Disabled Population in India

Intellectual disability in India is substantially under-reported, especially amongst females. This study quantifies the prevalence and gender bias in household reporting of intellectual disability by estimating the age-and-gender specific prevalence of the intellectually disabled by education, Socio-Demographic Index (SDI) score, place of residence, (rural/urban) and income of household head. We estimated prevalence (per 100,000) at 179 (95% CI: 173 to 185) for males and 120 (95% CI: 115 to 125) for females. Gender differences declined sharply with increased education, was higher for lower ages and low income and varied little by state development. Under-identification and under-reporting due to stigma are two plausible reasons for the gender differences in prevalence that increase with age.

Spectrum of Chromosomal Abnormalities Detected by Conventional Cytogenetic Analysis Following Invasive Prenatal Testing of Fetuses with Abnormal Ultrasound Scans

Objectives

The frequent association between malformations and chromosomal abnormalities is now well-established. This study looks at the incidence and type of chromosomal abnormalities detected by conventional cytogenetic analysis in women undergoing invasive tests following detection of fetal anomalies on antenatal scans as well as incidence of other genetic abnormalities detected by DNA analysis of fetuses with congenital anomalies that had a normal karyotype.

Materials and Methods

A retrospective, observational study of pregnant women undergoing invasive testing following identification of fetal anomalies by ultrasonography was carried out in a tertiary care facility, Vellore, India, between 2011 and 2018.

Results

169 women underwent an invasive diagnostic procedure following detection of fetal anomalies. The most common indication for doing fetal karyotype was the presence of major fetal structural anomalies (142/169, 84%) with over a third (48/142, 34%) having multisystem involvement. Fetal hydrops was the next most common indication, detected in 18/169 (10%) fetuses. Aneuploidy was seen 19 of 25 fetuses (76%) with an abnormal karyotype with autosomal aneuploidy accounting for 13 (68%) and sex chromosome aneuploidy for seven (37%) of the fetuses. One fetus had double aneuploidy. In fetuses with normal karyotype, no additional information was obtained from further genetic testing.

Conclusions

The overall detection rate of chromosomal abnormalities in our study using conventional cytogenetic analysis was 14.8%, the majority (72%) being associated with structural malformations, 20% with non-immune hydrops and 4% with soft markers. Abnormal karyotypes were seen in 12.7% of fetuses with structural malformations.

Attachment quality of children with ID and its link to maternal sensitivity and structuring

BACKGROUND

Attachment theory produced a fertile field of research and clinical application. Although the topic of attachment of children with intellectual disability (ID) has received increasing research attention over the past 15 years, the empirical evidence is still limited.

AIMS

We applied theoretical and empirical knowledge of parenting typically developing children to examine the mother-child relationship in the ID population. The aim was to examine maternal sensitivity and structuring and its association with children's attachment classification and their disability.

METHODS

Forty preschool children (mean age 47.25, range 26-75 months) with non-specific ID and their mothers participated in the study. The mean developmental age was 25.92 months (SD = 10.89), The DQ mean score was 55.45 (SD = 17.28). We assessed children's quality of attachment using the SSP and maternal interactive behavior using the Emotional Availability Scales.

OUTCOMES

Forty percent of children showed secure attachment, and 32.5% showed disorganized attachment. Attachment classifications correlated significantly with maternal sensitivity and maternal structuring but not with the child's cognitive disability.

CONCLUSIONS

The results point to the importance of maternal interactive behavior for children with ID. Clinical implication may consider interventions aiming to enhance maternal sensitivity and structuring to improve children's quality of attachment.

Prevalence of reported physical health problems in people with severe or profound intellectual and motor disabilities: a cross-sectional study of medical records and care plans

BACKGROUND

People with severe or profound intellectual and motor disabilities (SPIMD) experience numerous serious physical health problems and comorbidities. Knowledge regarding the prevalence of these problems is needed in order to detect and treat them at an early stage. Data concerning these problems in individuals with SPIMD are limited. Therefore, the aim of this study was to determine the prevalence of reported physical health problems in adults with SPIMD through a review of medical records and care plans.

METHOD

We conducted a cross-sectional study employing data obtained from medical and support records. A sample of adults with SPIMD was recruited in eight residential care settings. Physical health problems that had occurred during the previous 12 months or were chronic were recorded.

RESULTS

The records of 99 participants were included. A wide range of physical health problems were found with a mean of 12 problems per person. Very high prevalence rates (>50%) were found for constipation, visual impairment, epilepsy, spasticity, deformations, incontinence and reflux.

CONCLUSIONS

The results suggest that people with SPIMD simultaneously experience numerous, serious physical health problems. The reliance on reported problems may cause an underestimation of the prevalence of health problems with less visible signs and symptoms such as osteoporosis and thyroid dysfunction.

The impact of financing of screening tests on utilization and outcomes: The case of amniocentesis

We use a 1993 policy change in Israel's public healthcare system that lowered the eligibility age for amniocentesis to 35 to study the effects of financing of screening tests. Financing is found to have increased amniocentesis testing by about 35%. At ages above the eligibility threshold, utilization rates rose to roughly 33%, reflection nearly full takeup among prospective users of amniocentesis. Additionally, whereas below the age-35 threshold amniocentesis utilization rates increase with maternal age, this relation is muted above this age. Finally, no evidence is found that financing affects outcomes such as pregnancy terminations and births of children with Down syndrome. These results support the view that women above the eligibility threshold tend to refrain from acquiring inexpensive information about their degree of risk that absent the financing they would acquire, and instead, undergo the accurate and costly test regardless of additional information that noninvasive screening would provide.

Disparities in Substance Abuse Treatment Utilization Among Women with Intellectual Disability

Despite concerns about health disparities among women with intellectual disabilities, little is known about substance abuse treatment access in this population. Using standardized performance measures, treatment initiation and engagement were examined retrospectively for women aged 18 to 64 (N = 3,752), men with (N = 5,732) and women without intellectual disability (N = 493,446). Logistic regression models of utilization were conducted. Women in the sample were less likely than men in the sample or women without intellectual disability to utilize treatment, suggesting both gender-related and disability-related barriers. Policy and practice implications for improving the health and welfare of women with intellectual disabilities are discussed.

Trends in the prevalence of childhood disability: analysis of data from the national disability registry of Taiwan, 2000-2011

Childhood disability is not uncommon, but data at the national level are limited, especially those on the changes in the prevalence over time. On the basis of the Disabled Welfare Act, Taiwan began to certify disabled residents and provide various services in 1980. All the cases receiving services are registered, and the registry provides a rare opportunity for studying childhood disability at the national level. Using the data from 2000 to 2011, we calculated the age-specific prevalence of all disability combined and assessed the changes over time. We also calculated the prevalence rate and the proportion in all disabilities combined for each disability category and assessed the trends. As certification before 3 years old is generally discouraged by the government, we limited analyses to children between 3 and 17 years old. We found that the registered cases ranged from 49,242 to 61,717 from 2000 to 2011 and that intellectual disability (ID), had been the leading category all through the years. The proportion of autism spectrum disorders (ASD) had been increasing rapidly and become the third leading disability in 2011. The prevalence of all disabilities combined increased constantly from 9.98/1000 to 15.41/1000 (p<0.01), and increases were generally observed every year in all age groups (p<0.01). The increase could largely be attributable to the increases in ID and ASD, while the increasing trends were also significant in "multiple disabilities," "speech or language impairment," and "other disabilities listed by the Department of Health" (p<0.01 for all the five categories). An increase with age in the prevalence of all disabilities combined could be observed all through the years (p<0.01 in all calendar years). We concluded that the prevalence of childhood disability has been increasing in Taiwan, with ID contributing the most cases and ASD as an emerging problem. However, the increase of prevalence cannot be attributed entirely to the increase in the occurrence of cases, and an increase in the proportion of cases registered was an more important factor, which may be in turn attributable to a better service of the related agencies, lower discrimination against the patients, higher awareness of the disorder, and more willingness of the guardians to register.

Maternal conditions and perinatal characteristics associated with autism spectrum disorder and intellectual disability

Background

As well as being highly comorbid conditions, autism spectrum disorders (ASD) and intellectual disability (ID) share a number of clinically-relevant phenomena. This raises questions about similarities and overlap in diagnosis and aetiological pathways that may exist for both conditions.

Aims

To examine maternal conditions and perinatal factors for children diagnosed with an ASD, with or without ID, and children with ID of unknown cause, compared with unaffected children.

Methods

The study population comprised all live singleton births in Western Australia (WA) between January 1984 and December 1999 (N = 383,153). Univariate and multivariate multinomial logistic regression models were applied using a blocked modelling approach to assess the effect of maternal conditions, sociodemographic factors, labour and delivery characteristics and neonatal outcomes.

Results

In univariate analyses mild-moderate ID was associated with pregnancy hypertension, asthma, urinary tract infection, some types of ante-partum haemorrhage, any type of preterm birth, elective C-sections, breech presentation, poor fetal growth and need for resuscitation at birth, with all factors showing an increased risk. Severe ID was positively associated with poor fetal growth and need for resuscitation, as well as any labour or delivery complication. In the multivariate analysis no maternal conditions or perinatal factors were associated with an increased risk of ASD without ID. However, pregnancy hypertension and small head circumference were associated with a reduced risk (OR = 0.64, 95% CI: 0.43, 0.94; OR = 0.58, 95% CI: 0.34, 0.96, respectively). For ASD with ID, threatened abortion before 20 weeks gestation and poor fetal growth were associated with an increased risk.

Conclusion

Findings show that indicators of a poor intrauterine environment are associated with an elevated risk of ID, while for ASD, and particularly ASD without ID, the associations are much weaker. As such, these findings highlight the importance of accounting for the absence or presence of ID when examining ASD, if we are to improve our understanding of the causal pathways associated with these conditions.

Resolution of the diagnosis and maternal sensitivity among mothers of children with Intellectual Disability

We examined mothers' resolution of their children's diagnosis of Intellectual Disability (ID) and its link to maternal sensitivity, and we hypnotized that mothers' who are "resolved" will show more sensitivity during their interactions with their children than "unresolved" mothers. We assessed maternal resolution using the Reaction to Diagnosis Interview and maternal sensitivity in three different play episodes using the Emotional Availability Scales. Our sample included 40 children between the ages of 2.5 and 5.5 with clinical diagnoses of non-syndromic ID and their mothers. Supporting our hypothesis we found that mothers who were resolved regarding the diagnosis of their children showed more maternal sensitivity to their children in two of the three play episodes. Another important finding was that resolution and sensitivity were associated even when we controlled for the child's responsiveness to and involvement with the mother, suggesting that the link between resolution and sensitivity cannot be accounted by the impact of the child's behavior on the mother.

Gender and geographic differences in the prevalence of intellectual disability in children: analysis of data from the national disability registry of Taiwan

Intellectual disability (ID) is not uncommon in children, but data at the national level are limited, especially those on geographic differences. On the basis of the Disabled Welfare Law, Taiwan began to certify disabled residents and provide various services in 1980. All the cases are registered, and the registry provides a rare opportunity for studying ID at the national level. Using the data from 2004 to 2010, we calculated the prevalence of ID in children by age, gender, and geographic area and assessed the changes over time. We limited analyses to children at least 3 years of age, because certification before 3 years old is discouraged by the government. We found that from 2004 to 2010, the registered cases between 3 and 17 years old ranged from 20,531 to 23,547, and the prevalence of ID increased constantly from 4.40/1000 to 5.79/1000 (p<0.01), which generally increased every year in all age groups (p<0.01). In each year there were more boy cases than girl cases, and the boy-to-girl ratio generally decreased with age (p<0.01 for chi-square test for trend in all years). The prevalence rate ratio ranged from 1.33 to 1.37 (p<0.01 in all years), and the changes in the rate ratio were small over the years. We observed a higher prevalence in the rural areas over the years, and the prevalence rate ratio ranged from 1.34 to 1.43 (p<0.01 in all years), with an increasing trend over time (p<0.01).

Socioeconomic status and children with intellectual disability in China

BACKGROUND

Intellectual disability (ID) accounts for 70% of all disabilities among children in China's Second National Sampling Survey on Disability. Although studies have shown a relationship between social class and ID in children, none have investigated the association of socioeconomic variables in Chinese children with mild or severe ID.

METHODS

Data for children aged 0-6 years with and without ID were abstracted from the Second National Sampling Survey on Disability in China, conducted in 2006. Crude odds ratios showed the effect of sociodemographic factors on mild and severe ID. Adjusted odds ratios (OR(a) ) (95% confidence intervals) estimated the independent effects of these factors.

RESULTS

For both mild and severe ID, risk of having ID increased with male sex, birth to a woman aged 35 years and older, lower maternal education, mother's older age at delivery, lower income and rural residence. After age, gender and parent disability were controlled, mothers aged 35 years and older were more likely to have a child with ID: mild ID, OR(a) 1.47 (1.15-1.88); severe ID, OR(a) 1.32 (1.00-1.73). There was an approximate increasing monotonic risk of severe ID with increasing socioeconomic disadvantage: lowest income, OR(a) 3.00 (2.19-4.12); low income, OR(a) 2.28 (1.63-3.19); lower middle income, OR(a) 1.72 (1.27-2.33); middle income, OR(a) 1.73 (1.28-2.36).

CONCLUSIONS

There is a significant relationship between sociodemographic factors and ID. Similar patterns were found for both mild and severe ID. Recommendations are given for preventing ID in Chinese children.

College students' conceptualizations of deficits involved in mild intellectual disability

Precedential rulings in recent capital murder trials may, in some cases, leave it up to a jury to determine whether or not an individual meets criteria for an intellectual disability (ID) and should be spared from the death penalty. Despite the potential for misconceptions about ID to bias decisions, few empirical studies have examined the public's conceptualizations of individuals with ID. This study sought to examine 890 college students' conceptualizations of the deficits involved in mild ID. Students were asked to respond to two online surveys about the cognitive and adaptive behavior deficits that people with mild ID may experience. While most students were correct about basic facts, such as ID is not contagious and not curable, there was no clear consensus regarding beliefs about individuals with ID getting married, having children, or engaging in other mainstream activities of adult living. Students' responses are examined in light of results of studies that identify and examine bona fide deficits and areas of successful mainstreaming among persons with ID. Implications of misconceptions are discussed.

Effect of incorporating adaptive functioning scores on the prevalence of intellectual disability

Surveillance and epidemiologic research on intellectual disability often do not incorporate adaptive functioning (AF) data. Exclusion of AF data leads to overestimation of the prevalence of intellectual disability, the extent of which is not known. In this study, the authors evaluated the effect of incorporating AF data on overall intellectual disability prevalence according to sociodemographic, economic, and severity characteristics. Between 2002 and 2006, the Metropolitan Atlanta Developmental Disabilities Surveillance Program identified 1,595 8-year-old children who met the study's intellectual disability surveillance-case definition of IQ ≤ 70. AF scores were not available for 9.2% of the case children, specifically those with mild intellectual disability and low socioeconomic backgrounds. Prevalence estimates showed few substantive changes when incorporating AF data. The authors conclude that use of IQ data alone appears to be appropriate for measuring population intellectual disability prevalence.

Developmental and behavioral disorders through the life span

Developmental and behavioral disorders including intellectual disability, learning disabilities, and attention-deficit/hyperactivity disorder are highly prevalent, chronic health conditions. Despite being versed in caring for children with these conditions, pediatricians might be less prepared for challenging questions from families about the long-term course of these conditions and what can be done to improve outcomes. Through this state-of-the-art review, we provide clinicians with an understanding of the course of these conditions and adult outcomes in several areas including vocational, social, and health domains. We also provide a review of the most current research examining factors that predict or mediate adult outcomes for people with intellectual disability, learning disabilities, and attention-deficit/hyperactivity disorder. On the basis of the current literature, we offer practice recommendations aimed at optimizing adult outcomes for those with these disorders.

Demographic and clinical characteristics of people with intellectual disabilities with and without substance abuse disorders in a Medicaid population

Little is known about the demographic and clinical characteristics of people with intellectual disabilities and substance abuse problems. Drawing on health care billing claims for people with Medicaid coverage aged 12-99 years, the characteristics of people with intellectual disability and a history of substance abuse (N=9,484) were explored and compared with people with intellectual disability but without substance abuse. Age- and/or gender-adjusted odds ratios were derived from logistic regression analyses to consider differences in demographic and clinical diagnoses. People with intellectual disability and substance abuse constituted 2.6% of all people with intellectual disability, most of whom had a diagnosis of mild or moderate intellectual disability. People with intellectual disability and substance abuse problems were, on average, 2 years older than the comparison group and less likely to be White. The sample was more likely than the comparison group to have serious mental illness or depression and substance abuse-related disorders were not prevalent. These data provide a comparison point for existing studies of mental health diagnoses as well as new information about substance abuse disorders. Implications relate to the identification of substance abuse among people with intellectual disabilities as well as the establishment of demographic and clinical correlates.

Medicaid-covered alcohol and drug treatment use among people with intellectual disabilities: evidence of disparities

For some, community inclusion facilitates access to alcohol and drugs and, therefore, the potential for developing substance abuse disorders. However, little is known about substance abuse treatment use among people with intellectual disabilities. Using standardized performance measures, substance abuse treatment utilization was examined for Medicaid-covered people with intellectual disabilities and substance abuse (N=9,484) versus people without intellectual disabilities (N=915,070). The sociobehavioral model of healthcare use guides multivariate logistic regression analyses of substance abuse treatment utilization patterns, revealing disability-related disparities. Factors associated with utilization included being non-White, living in a nonurban area, having a serious mental illness, and living in a state with a generous Medicaid plan for substance abuse treatment. Implications relate to health policy, service delivery patterns, and the need for cross-system collaboration in the use of integrated treatment approaches.

Genetics of early onset cognitive impairment

Intellectual disability (ID) is the leading socio-economic problem of health care, but compared to autism and schizophrenia, it has received very little public attention. Important risk factors for ID are malnutrition, cultural deprivation, poor health care, and parental consanguinity. In the Western world, fetal alcohol exposure is the most common preventable cause. Most severe forms of ID have genetic causes. Cytogenetically detectable and submicroscopic chromosomal rearrangements account for approximately 25% of all cases. X-linked gene defects are responsible in 10-12% of males with ID; to date, 91 of these defects have been identified. In contrast, autosomal gene defects have been largely disregarded, but due to coordinated efforts and the advent of next-generation DNA sequencing, this is about to change. As shown for Fra(X) syndrome, this renewed focus on autosomal gene defects will pave the way for molecular diagnosis and prevention, shed more light on the pathogenesis of ID, and reveal new opportunities for therapy.

Prevalence of autism in an urban population of adults with severe intellectual disabilities--a preliminary study

BACKGROUND

Research on the prevalence of autism in Iceland has indicated that one possible explanation of fewer autism cases in older age groups was due to an underestimation of autism in individuals with intellectual disabilities (IDs). The present study systematically searched for autism cases in the adult population of individuals with severe ID living in the city of Reykjavik, Iceland.

METHODS

Potential participants (n = 256) were recruited through the Regional Office for the Affairs of the Handicapped in Reykjavik. First, a screening tool for autism was applied, followed by the Childhood Autism Rating Scale and finally the Autism Diagnostic Interview-Revised (ADI-R).

RESULTS

The point prevalence of severe ID was 3.7/1000 (95% CI 3.2-4.1) with a male-female ratio of 1.2:1. Participation rate in the study was 46.5%. Participants were younger than non-participants and more often residents of group homes. The prevalence of autism was 21% (25/119) (95% CI 14.7-29.2) with a male-female ratio of 1.8:1. Of the individuals with autism, 10/25 (40%) were verbal according to the ADI-R definition, and 18/25 (72%) had active epilepsy and/or other neurological conditions and handicaps.

CONCLUSION

The study identified twice the number of autism cases than those previously recognised within the service system. Autism is a prevalent additional handicap in individuals with severe ID, which should always be considered in this population. There are indications that the estimated prevalence of autism found should be considered minimal.

Prevalence of Overweight and Mothers’ Perception of Weight Status of Their Children With Intellectual Disabilities in South Korea

The purpose of this study was to estimate the prevalence of overweight and examine relationships between weight status of children with intellectual disabilities (IDs), mothers’ perceived weight status of children, and socioeconomic status (SES). A cross-sectional study of 206 mothers of children with IDs in six special schools in Seoul, South Korea, was conducted. Data were collected through school health record abstraction and parent survey during December 2004. Relationships between measures were assessed using chi-square (χ2) with Fisher’s exact test, analysis of variance (ANOVA), and logistic regression modeling while stratifying by mothers who overestimated versus underestimated their children’s weight status. Almost half (46.6%) of the children were overweight, and 72.8% of mothers accurately perceived their children’s weight status. Overweight among children with IDs in South Korea appears to be a more prevalent problem than expected. This study suggests the need for school-based weight management interventions for children with special needs.

The effect of maternal smoking during pregnancy on intellectual disabilities among 8-year-old children

Prenatal tobacco smoke exposure has been implicated as a risk factor for cognitive deficits in children. The purpose of this study is to examine the association between prenatal tobacco smoke exposure and diagnosis of intellectual disabilities (ID) among 8-year-old children living in Arkansas, Georgia, North Carolina and Utah. In 2002 and 2004, 965 ID case children were identified through a surveillance network and compared with the population of children born in the surveillance region during the same period (n = 104 607). Prenatal tobacco smoke exposure was determined from birth certificates. We estimated the effect of prenatal tobacco smoke exposure (none, <10, 10-19 and > or =20 cigarettes per day) on ID using logistic regression. Generally, the risk of ID was mildly elevated among children whose mothers smoked > or =20 cigarettes per day during pregnancy [RR 1.34; 95% (confidence interval) CI 0.96, 1.87] after adjustment for maternal education, maternal race, maternal age, marital status, child sex, birth year and study site. However, the effect of exposure to > or =20 cigarettes per day significantly differed for males [RR 1.77, 95% CI 1.20, 2.62] compared with females [RR 0.81, 95% CI 0.44, 1.50]. Supplemental analyses reveal substantial confounding of this relationship by socio-economic indicators. A differential effect of tobacco smoke exposure on the risk of ID is suggested for males and females and deserves further investigation; however, the interpretation is tempered by the potential for residual confounding.

Impact of additional disabilities on adaptive behavior and support profiles for people with intellectual disabilities

Numerous researchers have reported a high incidence of additional disabilities coexisting with intellectual disabilities. Although an intuitive link can be made between the existence of multiple disabilities and greater need for support, little has been reported about this relationship. Using measures of adaptive functioning and support needs, we examined the extent to which adaptive and challenging behaviors and consequent support needs (including medical) were impacted by the presence and severity of additional disabilities for individuals with intellectual disabilities. Results show that adaptive behaviors and support needs were meaningfully related to the number and severity of additional disabilities present, whereas this was not so for challenging behaviors. Findings are discussed in terms of contemporary models of disability and functioning.

Verbal, visual, and spatio-sequential short-term memory: assessment of the storage capacities of children and teenagers with Down's syndrome

BACKGROUND

It is recognized that individuals with Down's syndrome have a specific deficit in verbal short-term memory. On the other hand, non-verbal short-term memory seems to be preserved or even be a strong point for these persons. Nevertheless, the extent and specificity of the deficit must be determined. To do so, we carried out a research programme that allowed us to simultaneously assess various short-term memory systems in a developmental perspective, and to compare our participants' performance to that obtained by typically developing individuals of the same mental age.

METHOD

Three span tasks are used (auditory word span/visual patterns test/Corsi blocks task) with 54 children and teenagers with Down's syndrome and 54 typically developing children as control group. Participants were matched according to their cognitive level.

RESULTS

For the auditory word span task, participants with Down's syndrome obtained performances significantly lower than those of the typically developing participants. On the other hand, compared with typically developing children, children and teenagers with Down's syndrome have a spatio-sequential span significantly higher for the lowest developmental ages. No significant differences were found for visual span.

CONCLUSIONS

Individuals with Down's syndrome exhibited a distinctive pattern of memory performance, in addition to their developmental specificities.

CC2D2A, encoding a coiled-coil and C2 domain protein, causes autosomal-recessive mental retardation with retinitis pigmentosa

Autosomal-recessive inheritance is believed to be relatively common in mental retardation (MR), although only four genes for nonsyndromic autosomal-recessive mental retardation (ARMR) have been reported. In this study, we ascertained a consanguineous Pakistani family with ARMR in four living individuals from three branches of the family, plus an additional affected individual later identified as a phenocopy. Retinitis pigmentosa was present in affected individuals, but no other features suggestive of a syndromic form of MR were found. We used Affymetrix 500K microarrays to perform homozygosity mapping and identified a homozygous and haploidentical region of 11.2 Mb on chromosome 4p15.33-p15.2. Linkage analysis across this region produced a maximum two-point LOD score of 3.59. We sequenced genes within the critical region and identified a homozygous splice-site mutation segregating in the family, within a coiled-coil and C2 domain-containing gene, CC2D2A. This mutation leads to the skipping of exon 19, resulting in a frameshift and a truncated protein lacking the C2 domain. Conservation analysis for CC2D2A suggests a functional domain near the C terminus as well as the C2 domain. Preliminary functional studies of CC2D2A suggest a possible role in Ca(2+)-dependent signal transduction. Identifying the function of CC2D2A, and a possible common pathway with CC2D1A, in correct neuronal development and functioning may help identify possible therapeutic targets for MR.

Mental retardation in children ages 6 to 16

Mental retardation (MR) is a life long condition that affects 6 million American and 560,000 Canadian children under the age of 14. This review discusses the definition of MR, an approach to investigation, common comorbidities, and a general approach to management.

Mild cognitive impairment in early life and mental health problems in adulthood

OBJECTIVES

We assessed the extent to which borderline mental retardation and mental retardation at preschool ages are related to emotional and behavioral problems in young adulthood. We also explored early risk factors for having mental health problems as a young adult that might be related to preschool differences in cognitive ability.

METHODS

We used data from a cohort of births studied in the Johns Hopkins Collaborative Perinatal Study and followed up in the Pathways to Adulthood Study. Preschool cognitive functioning was assessed at 4 years of age. Individual characteristics, psychosocial factors, and mental problems were prospectively evaluated from birth through young adulthood.

RESULTS

Children with subaverage cognitive abilities were more likely to develop mental health problems than their counterparts with IQs above 80. Inadequate family interactions were shown to increase 2- to 4-fold the risk of emotional or behavioral problems among children with borderline mental retardation.

CONCLUSIONS

Subaverage cognitive functioning in early life increases later risk of mental health problems. Future research may help to delineate possible impediments faced at different developmental stages and guide changes in supportive services to better address the needs of children with borderline mental retardation.

The effects of PCBs and dioxins on child health

BACKGROUND/EXPOSURE: Dioxins and PCBs are highly persistent and highly toxic environmental pollutants which at present are derived mainly from waste incineration and food contamination. They are widespread in nature and pollute human food, including breast milk so that basically all children in Europe are exposed to measurable levels. RESULTS/TOXICITY IN CHILDREN: The toxicity of dioxins and PCBs are well described both from animal studies and from a number of human epidemiological studies including several large cohort studies. Especially developmental exposure has been shown to affect endocrine and cognitive systems negatively. Measurable outcomes include reduced IQ and changed behaviour. Foetotoxic effects with reduced birth weight and increased congenital anomalies such as cleft lip have also been described. Exposure to PCBs and dioxins must be considered also in the context of multiple exposure to several toxins simultaneously or sequentially. CONCLUSION/SUGGESTED ACTION: Some measures aimed at reducing exposure to dioxins have been partly successful in that the dioxin content of breast milk is going down. However, further steps to reduce exposure must be taken. We suggest legislative measures for reducing the re-entry of especially PCBs from waste into the environment. Individual pre-conception counselling is recommended in order to reduce developmental exposure and its consequences. Biomonitoring of the substances themselves in breast milk and foods is recommended as well as monitoring possible endocrine effects.

A population-based study of the recurrence of developmental disabilities--Metropolitan Atlanta Developmental Disabilities Surveillance Program, 1991-94

Serious developmental disabilities (DD) are quite common and affect approximately 2% of all school-aged children. The impact of DDs with respect to the need for special education services, medical care and the demand on family members can be enormous. While this impact can be magnified for families with more than one child with a DD, little is known regarding the epidemiology of recurrence of DDs. When the cause of a DD is unknown, genetic counsellors rely on recurrence risk estimates which for DDs are over 10 years old. The objectives of our study were to: (1) assess the contribution of recurrent cases to the prevalence of DDs; (2) provide current, population-based recurrence risk estimates; and (3) examine characteristics of the first affected child as predictors of recurrence. Two population-based data sources were used to identify all children born to the same mother during the period 1981-91 in the five-county metropolitan Atlanta area with at least one of four DDs: mental retardation (MR), cerebral palsy, hearing loss, or vision impairment. Recurrence risk estimates for these DDs ranged from 3% to 7% and were many times higher than the background prevalences. The risk of recurrence of DDs was greatest for MR - approximately eight times greater than the baseline MR prevalence. Isolated mild MR (IQ 50-70) was highly concordant between siblings with MR. Sex, race, and birthweight of the index child, maternal education, and maternal age were not significantly associated with recurrence risk. Further research is needed to investigate the roles of genetic and environmental factors on the recurrence of DDs, particularly isolated mild MR.

Prevalence of intellectual disability in Western Australia

Record linkage of multiple sources was used to ascertain children with intellectual disability born in Western Australia between 1983 and 1992. The prevalence was 14.3 per 1000, 10.6 per 1000 for children with mild or moderate and 1.4 per 1000 for those with a severe level of intellectual disability. Prevalence was greater in males (prevalence ratio 1.6) and in children of Aboriginal mothers (prevalence ratio 2.3). Although prevalence of intellectual disability has been found to vary according to study location, method of ascertainment and criteria used, these estimates are similar to estimates from several recent studies.

The epidemiology of mental retardation: challenges and opportunities in the new millennium

There are a number of problems and challenges in relating the science of epidemiology to mental retardation (MR). These relate to how MR is defined and classified and how these definitions may change over time. These as well as other differences in ascertainment sources and methods need to be considered when comparing MR prevalence over time and place. On the other hand, advances in technology also provide new and efficient methods of data collection both by data linkage and by use of web-based methods to study rare diseases. While prevalence studies have not been individually reviewed, we have examined the range of data including recent studies relating to how prevalence differs according to age, gender, social class and ethnicity. Some problems with available etiological classification systems have been identified. Recent etiological studies, most of which use different classification systems, have been reviewed and explanations have been postulated to account for differences in results. Individual risk factors for MR are considered whilst the option of considering a population as opposed to a high risk strategy to MR prevention is raised. This might well involve improving the social milieu surrounding the occurrence of individual risk factors. The impact of biotechnological advances such as antenatal and neonatal screening and assisted reproduction on MR are discussed. The issue of how inequalities in access to technology may impact on case identification and even have the potential to further widen inequalities is raised. The importance of extending the use of epidemiological tools to study the social, health and economic burden of MR is also emphasized. However, in order to apply to MR the "prevention-intervention-research" cycle, which surely underpins all epidemiology, it is vital to ensure that the methodological challenges we raise are adequately addressed.

Increased risk for developmental disabilities in children who have major birth defects: a population-based study

OBJECTIVE

We sought to quantify the strength of associations between each of four specific developmental disabilities (DDs) and specific types of major birth defects.

METHODS

We linked data from 2 independent surveillance systems, the Metropolitan Atlanta Congenital Defects Program and the Metropolitan Atlanta Developmental Disabilities Surveillance Program. Children with major birth defects (n = 9142; born 1981-1991 in metro Atlanta) and 3- to 10-year-old children who were born between 1981 and 1991 in metro Atlanta and identified between 1991 and 1994 as having mental retardation, cerebral palsy, hearing impairment, or vision impairment (n = 3685) were studied. Prevalence ratio (PR), which is the prevalence of a DD in children with 1 or more major birth defects divided by the prevalence of the same DD in children without major birth defects, was measured.

RESULTS

Among the 9142 children who were born with a major birth defect, 657 (7.2%) had a serious DD compared with 0.9% in children with no major birth defect, yielding a PR of 8.3 (95% confidence interval: 7.6-9.0). In general, the more severe the DD, the higher was the PR. Birth defects that originated in the nervous system and chromosomal defects resulted in the highest PRs for a subsequent DD. For all other categories of birth defects, PRs were lowest when all major birth defects present were confined to a single category (ie, isolated defects). PRs for any DD increased monotonically with the number of coded birth defects per child or the number of different birth defect categories per child, regardless of the severity of the defect or whether defects of the nervous system, chromosomal defects, or "other syndromes" were counted.

CONCLUSIONS

These data highlight the possible early prenatal origins of some DDs and suggest that both the number of coded birth defects present and the number of anatomic systems involved are strongly related to functional outcomes.