Social class and infantile autism

Socioeconomic status and the risk of suspected autism spectrum disorders among 18-month-old toddlers in Japan: a population-based study

The association between family socioeconomic status (SES) and the suspected autism spectrum disorder (ASD) status of 18-month-old toddlers was investigated using a population-based sample in Japan, which has a universal healthcare system and a mandatory health checkup system for toddlers. Questionnaires including SES measurements and modified checklist for autism in toddlers were mailed to all families with 18-month-old toddlers in Chiba, a city near Tokyo (N = 6,061; response rate: 64%). The results of logistic regression analysis (which were adjusted for potential confounders) indicated that low maternal education, but not paternal education or family income, were associated with having suspected ASD offspring. Lower maternal education was associated with an increased risk of autistic traits in Japan.

Parental socioeconomic status and risk of offspring autism spectrum disorders in a Swedish population-based study

OBJECTIVE

Epidemiological studies in the United States consistently find autism spectrum disorders (ASD) to be overrepresented in high socioeconomic status (SES) families. These findings starkly contrast with SES gradients of many health conditions, and may result from SES inequalities in access to services. We hypothesized that prenatal measures of low, not high, parental SES would be associated with an increased risk of offspring ASD, once biases in case ascertainment are minimized.

METHOD

We tested this hypothesis in a population-based study in Sweden, a country that has free universal healthcare, routine screening for developmental problems, and thorough protocols for diagnoses of ASD. In a case-control study nested in a total population cohort of children aged 0 to 17 years living in Stockholm County between 2001 and 2007 (N = 589,114), we matched ASD cases (n = 4,709) by age and sex to 10 randomly selected controls. We retrieved parental SES measures collected at time of birth by record linkage.

RESULTS

Children of families with lower income, and of parents with manual occupations (OR = 1.4, 95% CI = 1.3-1.6) were at higher risk of ASD. No important relationships with parental education were observed. These associations were present after accounting for parental ages, migration status, parity, psychiatric service use, maternal smoking during pregnancy, and birth characteristics; and regardless of comorbid intellectual disability.

CONCLUSIONS

Lower, not higher, socioeconomic status was associated with an increased risk of ASD. Studies finding the opposite may be underestimating the burden of ASD in lower SES groups.

Socioeconomic inequality in the prevalence of autism spectrum disorder: evidence from a U.S. cross-sectional study

BACKGROUND

This study was designed to evaluate the hypothesis that the prevalence of autism spectrum disorder (ASD) among children in the United States is positively associated with socioeconomic status (SES).

METHODS

A cross-sectional study was implemented with data from the Autism and Developmental Disabilities Monitoring Network, a multiple source surveillance system that incorporates data from educational and health care sources to determine the number of 8-year-old children with ASD among defined populations. For the years 2002 and 2004, there were 3,680 children with ASD among a population of 557,689 8-year-old children. Area-level census SES indicators were used to compute ASD prevalence by SES tertiles of the population.

RESULTS

Prevalence increased with increasing SES in a dose-response manner, with prevalence ratios relative to medium SES of 0.70 (95% confidence interval [CI] 0.64, 0.76) for low SES, and of 1.25 (95% CI 1.16, 1.35) for high SES, (P<0.001). Significant SES gradients were observed for children with and without a pre-existing ASD diagnosis, and in analyses stratified by gender, race/ethnicity, and surveillance data source. The SES gradient was significantly stronger in children with a pre-existing diagnosis than in those meeting criteria for ASD but with no previous record of an ASD diagnosis (p<0.001), and was not present in children with co-occurring ASD and intellectual disability.

CONCLUSIONS

The stronger SES gradient in ASD prevalence in children with versus without a pre-existing ASD diagnosis points to potential ascertainment or diagnostic bias and to the possibility of SES disparity in access to services for children with autism. Further research is needed to confirm and understand the sources of this disparity so that policy implications can be drawn. Consideration should also be given to the possibility that there may be causal mechanisms or confounding factors associated with both high SES and vulnerability to ASD.

Possible association between the androgen receptor gene and autism spectrum disorder

Autism is a highly heritable disorder but the specific genes involved remain largely unknown. The higher prevalence of autism in men than in women, in conjunction with a number of other observations, has led to the suggestion that prenatal brain exposure to androgens may be of importance for the development of this condition. Prompted by this hypothesis, we investigated the potential influence of variation in the androgen receptor (AR) gene on the susceptibility for autism. To this end, 267 subjects with autism spectrum disorder and 617 controls were genotyped for three polymorphisms in exon 1 of the AR gene: the CAG repeat, the GGN repeat and the rs6152 SNP. In addition, parents and affected siblings were genotyped for 118 and 32 of the cases, respectively. Case-control comparisons revealed higher prevalence of short CAG alleles as well as of the A allele of the rs6152 SNP in female cases than in controls, but revealed no significant differences with respect to the GGN repeat. Analysis of the 118 families using transmission disequilibrium test, on the other hand, suggested an association with the GGN polymorphism, the rare 20-repeat allele being undertransmitted to male cases and the 23-repeat allele being overtransmitted to female cases. Sequencing of the AR gene in 46 patients revealed no mutations or rare variants. The results lend some support for an influence of the studied polymorphisms on the susceptibility for autism, but argue against the possibility that mutations in the AR gene are common in subjects with this condition.

School district resources and identification of children with autistic disorder

OBJECTIVES

We estimated the effect of community and school district resources on the identification of children with autistic disorder.

METHODS

Latent growth curve regression models were applied to school district-level data from one large state.

RESULTS

The rate of identification of autistic disorder increased on average by 1.0 child per 10000 per year (P<.001), with statistically significant district variation. After adjustment for district and community characteristics, each increase in decile of school revenue was associated with an increase of 0.16 per 10000 children identified with autistic disorder. The proportion of economically disadvantaged children per district was inversely associated with autistic disorder cases.

CONCLUSIONS

District revenue was associated with higher proportions of children identified with autistic disorder at baseline and increasing rates of identification when measured longitudinally. Economically disadvantaged communities may need assistance to identify children with autistic spectrum disorders and other developmental delays that require attention.

Descriptive epidemiology of autism in a California population: who is at risk?

We investigated the association between selected infant and maternal characteristics and autism risk. Children with autism born in California in 1989-1994 were identified through service agency records and compared with the total population of California live births for selected characteristics recorded on the birth certificate. Multivariate models were used to generate adjusted risk estimates. From a live birth population of more than 3.5 million, 4381 children with autism were identified. Increased risks were observed for males, multiple births, and children born to black mothers. Risk increased as maternal age and maternal education increased. Children born to immigrant mothers had similar or decreased risk compared with California-born mothers. Environmental factors associated with these demographic characteristics may interact with genetic vulnerability to increase the risk of autism.

Descriptive epidemiology of autism in a California population: who is at risk?

We investigated the association between selected infant and maternal characteristics and autism risk. Children with autism born in California in 1989-1994 were identified through service agency records and compared with the total population of California live births for selected characteristics recorded on the birth certificate. Multivariate models were used to generate adjusted risk estimates. From a live birth population of more than 3.5 million, 4381 children with autism were identified. Increased risks were observed for males, multiple births, and children born to black mothers. Risk increased as maternal age and maternal education increased. Children born to immigrant mothers had similar or decreased risk compared with California-born mothers. Environmental factors associated with these demographic characteristics may interact with genetic vulnerability to increase the risk of autism.

Epidemiology of autism in Singapore: findings of the first autism survey

The report describes the results of a survey conducted on 176 parents of children with autism in Singapore. The ages of the children ranged from 3 to 12 years. The survey focused on the child's background, behaviour problems and skill profile, the home and school situation as well as the linguistic and social background. It was noted that the Singapore population confirms the international distribution regarding a predominance of boys over girls and a low incidence of birth complications. A positive trend noted was the fact that 60% of the children were diagnosed before the age of 3 years. Discussion focuses on possible risk factors and psychosocial adversities for autism such as a high frequency of caregivers who are foreign maids, the use of multiple languages and the high level of punitive educational practices. The possible influence of psychosocial deprivation on child development is discussed.

Asperger syndrome and high-functioning autism

This paper reviews the history of Asperger syndrome (AS) and high-functioning autism (HFA), current diagnostic concepts and criteria, some controversial diagnostic issues, epidemiology, background factors, outcome, and intervention guidelines.

A comparison of speaking and mute individuals with autism and autistic-like conditions on the Autism Behavior Checklist

The item, total, and subscale scores on the Autism Behavior Checklist (ABC) were compared for 155 mute and 335 speaking individuals with autism spectrum disorders. Although no significant difference was observed between the groups on the ABC total score, the mute group demonstrated significantly more pathology on 21 of 57 items and 3 of 5 subscales. The speaking group obtained significantly higher scores on only 8 items and 1 subscale (Language). The appropriateness of providing greater pathology scores on expressive language items to speaking, rather than to mute, individuals is called into question. The authors speculate whether the expressive language items are weighted too heavily, in regard both to the Language subscale and to the ABC total score. If the expressive language items were removed, the mute group would have significantly higher ABC total scores and therefore a greater degree of autism severity.

Psychophysiological aspects of autistic disorders: overview

The neurological, neurochemical, and neurotransmitter level differences as well as genetic influences associated with autism have been studied extensively in the last two decades. The varied findings from research offer hope for better understanding, effective treatment, and, perhaps, cure of this pervasive developmental disorder.

Children with deficits in attention, motor control and perception (DAMP) almost grown up: The contribution of various background factors to outcome at age 16 years

Fifty-six children with and forty-five children without deficits in attention, motor control and perception (DAMP) had been recruited from the general population at age 7 years. They were followed up neuropsychiatrically at age 16 years after intermediate term follow up at age 10 and 13 years. Cases were subdivided into those with good and not good outcome on the basis of absence or presence of psychiatric and personality disorders, multiple traumatic accidents and speech and language problems at age 16 years. The presence of DAMP in itself was the strongest predictor of poor outcome. High scores for minor neurological dysfunction, low performance IQ, autistic features at age 7 years and poor reading skills at age 10 and/or 13 years were important background factors in cases with poor outcome. In the small subgroup with poor outcome among those without DAMP at age 7 years, major life events was the most important background factor.

The definition and prevalence of autism: A review

Sixteen studies of the prevalence of autism in childhood, using epidemiological methods in defined populations in Europe, the USA and Japan, in English or with English summaries, were found in the published literature. Age specific rates varied from 3.3 to 16.0 per 10,000. Eight studies gave rates for a sub-group of 'typical' autism varying from 1.2 to 8.4. Reasons for variations were sought by examining geographic and demographic details of the populations screened, methods for initial screening and final examination of possibly autistic children, demographic and clinical details of children identified as autistic, and criteria used for diagnosis. There was evidence, independent of diagnostic criteria, of a higher prevalence among children of first generation immigrants to Europe from 'exotic' countries. Apart from this, all differences could be due to variations in diagnostic practice and increasing awareness of the manifestations of autistic conditions throughout the range of intelligence, from severely retarded to average and above. However, it remains possible, though not proven, that rates do vary over place and/or time. The problems of defining a sub-group with 'typical' autism among the wide spectrum of children with the triad of impairments of social interaction, communication and imagination are discussed and the value of such a sub-grouping questioned.

The Emanuel Miller Memorial Lecture 1991. Autism and autistic-like conditions: subclasses among disorders of empathy

Recent autism and autism-related research from Gothenburg is surveyed. In indigenous families, typical autism seems no more common now than 10 years ago. Genetic factors play a part in causing autism and Asperger syndrome. Certain medical syndromes carry a relatively high risk of concomitant autistic symptoms. Evidence for non-specific brain dysfunction is often found in autism and autistic-like conditions. The search for the underlying clue to the riddle of autism may be futile. Autism might be best conceptualized as a behavioural syndrome reflecting underlying brain dysfunction which shades into other clinical syndromes. A new class of disorders of empathy is proposed.

Neuropsychiatric assessment of children with autism: a population-based study

Thirty-five children with autistic disorder and 17 with autistic-like conditions underwent an exhaustive neurobiological evaluation, and the findings were contrasted with those obtained from various comparison groups. Almost 90 per cent of the children with autistic disorder and autistic-like conditions had major indications of brain damage or dysfunction. Some of those who did not show such abnormalities had a first-degree relative with Asperger syndrome. The rate of abnormality was similar to that of severely mentally retarded children, but in excess of that of normal children. Within the autism group, abnormality rate did not correlate with degree of mental retardation. It is concluded that autism has multiple biological aetiologies and that autistic symptoms in a child should always prompt a thorough medical/neurobiological evaluation.

The family background in anorexia nervosa: a population-based study

A group of 51 cases with anorexia nervosa (including a total population of cases from one birth cohort) was compared with a sex-, age- and school-matched group of 51 cases on various measures of family demography and interactions. There was no support for the notion of a "typical anorexia nervosa family." However, there were more major problems in the anorexia group and there was also a higher prevalence of dead first-degree relatives and depression in the mothers.

Is autism more common now than ten years ago?

A total population study of children, aged 13 years and under, suggested that there has been an apparent rise in the frequency of autistic disorder and autistic-like conditions (excluding Asperger's syndrome) in one area of western Sweden over the last ten years. The frequency was 4.0/100,000 in 1980, 7.5/10,000 in 1984 and 11.6/10,000 in 1988 in the city of Göteborg. Even though the prevalence rates refer to slightly different age cohorts, it was concluded that the apparent increase is in part due to better detection, but also to new cases born to immigrant parents. Typical cases of autistic disorder accounted for 75% of cases, and 20% had normal or near-normal IQs.

Autism under age 3 years: a clinical study of 28 cases referred for autistic symptoms in infancy

Twenty-eight children referred with a preliminary diagnosis of autistic disorder under age 3 yrs were extensively examined from the neuropsychiatric point of view and followed up for several months to several years. A diagnosis of autistic disorder was confirmed in 75% of the cases. A variety of associated medical conditions was identified. It was concluded that autism can be diagnosed in a substantial proportion of cases before age 3 yrs and that the neurobiological background is similar to that seen in older autistic children.

Do children with autism have March birthdays?

One hundred people with autistic disorder (DSM-III-R) without a known cause who comprised a total population of children with autism were compared with "autistic-like" children, Asperger syndrome and age-matched comparison children from the general population and were examined with regard to month of birth. There was an excess of March birth in the group of children with autism. The possible reasons for this finding are discussed.

A follow-up study of infantile autism in Hong Kong

All 87 autistic children referred to the Department of Psychiatry from 1976 to 1986 were included as subjects. Their demographic, family, medical, and psychiatric characteristics were described. Sixty-six (75.9%) were traced for follow-up assessment. There was a striking similarity between the characteristics of our sample and those reported in other countries (e.g., sex ratio, intelligence, language ability, behavioral characteristics, and outcome). The finding of less family history of language delay, epilepsy, and sex difference are discussed.

Asperger syndrome in 23 Swedish children

Twenty-three Swedish children aged five to 18 years who fulfilled specific criteria for Asperger syndrome were examined and compared with an age- and IQ-matched group with infantile autism. The boy:girl ratio was 10:1. Less than 10 per cent were mentally retarded and 17 per cent were of above-average intelligence. Apart from motor clumsiness (very common in the Asperger group) and reduced optimality in the prenatal and perinatal periods (more common in the autistic group), there was very little in the clinical or neurobiological backgrounds to suggest a clear distinction between Asperger syndrome and infantile autism.

A twin study of autism in Denmark, Finland, Iceland, Norway and Sweden

The Nordic countries were screened for the occurrence of cases of autism with a same-sexed twin under age 25 years. Twenty-one pairs (11 monozygotic and 10 dizygotic) of twins and one set of identical triplets were found and extensively examined. The concordance for autism by pair was 91% in the monoygotic and 0% in the dizygotic pairs. The corresponding concordances for cognitive disorder were 91% and 30%, respectively. In most of the pairs discordant for autism, the autistic twin had more perinatal stress. The results lend support for the notion that autism sometimes has a hereditary component and that perinatal stress is involved in some cases.

New perspectives in autism, Part II: The differential diagnosis and neurobiology of autism

The clinical spectrum of autism spans a broad range of functions, but the core symptoms remain the same regardless of the intelligence of the child: the autistic type of social deficit that ranges from a lack of inclination to relate to extreme difficulty with the mechanics of social interactions, a global communication deficit that involves both verbal and nonverbal modes, and a severe cognitive deficit involving concept formation (abstraction) that is combined with an exceptional memory for factual information. These symptoms may vary dramatically in severity, but the basic deficits are identifiable regardless of IQ. Under-recognition of autism is a major problem at all IQs, but especially in patients with IQs above 50. No drugs have been found to significantly improve the core deficits in autism. Antipsychotics should be avoided except for short-term use. Antidepressants, anxiolytics, and anticonvulsants are important in the treatment of depression, affective modulation, situation-related stress, and seizures. Intensive social skills training is assuming a prominent role in behavior modification programs, and success with higher-functioning autistic children suggests that outcome can be improved by intensive training. The neurobiology of autism has also undergone dramatic changes. The psychogenic theories of etiology have been completely invalidated. Autism is now considered to be a neurological disorder resulting from an error in brain development. The precise location and nature of this deficit are still being actively debated and investigated. One theory emphasizes a dysfunction of the limbic system that results in an impairment in the acquisition of information. A second theory proposes a primary role for dysfunction of the cortical association network responsible for the processing of information.

Neurobiological findings in 20 relatively gifted children with Kanner-type autism or Asperger syndrome

Seventeen children with classical Kanner autism and three children with Asperger syndrome, all of whom had Full-scale IQs above 65, were subjected to a neurobiological assessment, including CAT scan, auditory brainstem response, EEG, chromosomal cultures, cerebrospinal fluid, blood and urine examinations and a thorough physical examination. 15 of the 20 children had 'definite abnormalities' on at least one of these examinations. It is concluded that the number of cases of 'non-organic' autism, even among children with relatively higher intelligence, dwindles rapidly as our neurobiological assessment methods become increasingly sophisticated.

Infantile autism in children of immigrant parents. A population-based study from Göteborg, Sweden

A population-based study of infantile autism from western Sweden has been completed. Urban children with autism more often than age-matched children in the general population had immigrant parents from 'exotic' countries. No such trend was seen in rural children with infantile autism.

Autism and autistic-like conditions in Swedish rural and urban areas: a population study

The total population of children under 10 years in one Swedish urban area and one rural area was screened for infantile autism (IA) and autistic-like conditions (AC). A total prevalence of 6.6 per 10 000 was found, which is somewhat higher than in previous similar studies of the same region. Infantile autism accounted for two-thirds of the cases. Boys far outnumbered girls, but this was entirely accounted for by the IA group. The preponderance of autistic boys was less pronounced among the severely mentally retarded children. Mental retardation was seen in almost 90% of cases and only one child had an IQ exceeding 100; clinical and laboratory signs of brain dysfunction were also found in a majority of cases. Distribution by social class was no different in either patient group from the general population.

Familial heterogeneity in infantile autism

The incidence of autism and cognitive disability was assessed in the biological siblings of 29 autistic probands subdivided on the basis of IQ. A significant clustering of autism and nonspecific intellectual retardation was found in the siblings of severely retarded autistic probands which was not present in the siblings of our higher-functioning autistic sample. These findings suggest that there may be etiological differences in autism, depending on the degree of associated mental retardation.

Infantile autism: a total population study of reduced optimality in the pre-, peri-, and neonatal period

Twenty-five autistic children, constituting a total population sample of children with infantile autism, were compared with 25 sex- and maternity-clinic-matched controls for occurrence of reduced optimality in the pre-, peri, and neonatal period, as noted in medical records. Autistic children showed greatly increased scores for reduced optimality, especially with regard to prenatal factors. The findings are at odds with early reports that children with autism had not suffered potential brain injury. The reasons for the discrepancy are discussed.