Prevalence of Autism Spectrum Disorder in Children in Andalusia (Spain)

Autism Spectrum Disorder (ASD) is socially relevant because of its number and the intensity of the medical and socio-educational response it requires. In Andalusia, one in 70 children will be diagnosed with ASD in 2021. It is much more frequent in boys than in girls, being 5.91 times more likely to present it as a boy than as a girl. The age of diagnosis is increasingly younger, standing at 4.4 years. In more than half of primary schools and more than 75% of secondary schools there are an average of three students with ASD per school. It is necessary to develop a network of preferential care centers for students with ASD to generalize specialized care in ordinary modalities.

What Is the Male-to-Female Ratio in Autism Spectrum Disorder? A Systematic Review and Meta-Analysis

OBJECTIVE

To derive the first systematically calculated estimate of the relative proportion of boys and girls with autism spectrum disorder (ASD) through a meta-analysis of prevalence studies conducted since the introduction of the DSM-IV and the International Classification of Diseases, Tenth Revision.

METHOD

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. The Medline, Embase, and PsycINFO databases were searched, and study quality was rated using a risk-of-bias tool. Random-effects meta-analysis was used. The pooled outcome measurement was the male-to-female odds ratio (MFOR), namely the odds of being male in the group with ASD compared with the non-ASD group. In effect, this is the ASD male-to-female ratio, controlling for the male-to-female ratio among participants without ASD.

RESULTS

Fifty-four studies were analyzed, with 13,784,284 participants, of whom 53,712 had ASD (43,972 boys and 9,740 girls). The overall pooled MFOR was 4.20 (95% CI 3.84-4.60), but there was very substantial between-study variability (I² = 90.9%). High-quality studies had a lower MFOR (3.32; 95% CI 2.88-3.84). Studies that screened the general population to identify participants regardless of whether they already had an ASD diagnosis showed a lower MFOR (3.25; 95% CI 2.93-3.62) than studies that only ascertained participants with a pre-existing ASD diagnosis (MFOR 4.56; 95% CI 4.10-5.07).

CONCLUSION

Of children meeting criteria for ASD, the true male-to-female ratio is not 4:1, as is often assumed; rather, it is closer to 3:1. There appears to be a diagnostic gender bias, meaning that girls who meet criteria for ASD are at disproportionate risk of not receiving a clinical diagnosis.

Vitamin D and Autism Spectrum Disorder: A Literature Review

Low vitamin D status in early development has been hypothesised as an environmental risk factor for Autism Spectrum Disorder (ASD), given the concurrent increase in the prevalence of these two conditions, and the association of vitamin D with many ASD-associated medical conditions. Identification of vitamin D-ASD factors may provide indications for primary and secondary prevention interventions. We systematically reviewed the literature for studies on vitamin D-ASD relationship, including potential mechanistic pathways. We identified seven specific areas, including: latitude, season of conception/birth, maternal migration/ethnicity, vitamin D status of mothers and ASD patients, and vitamin D intervention to prevent and treat ASD. Due to differences in the methodological procedures and inconsistent results, drawing conclusions from the first three areas is difficult. Using a more direct measure of vitamin D status—that is, serum 25(OH)D level during pregnancy or childhood—we found growing evidence for a relationship between vitamin D and ASD. These findings are supported by convincing evidence from experimental studies investigating the mechanistic pathways. However, with few primary and secondary prevention intervention trials, this relationship cannot be determined, unless randomised placebo-controlled trials of vitamin D as a preventive or disease-modifying measure in ASD patients are available.

Lactic acid bacteria as a cell factory for the delivery of functional biomolecules and ingredients in cereal-based beverages: a review

In this review, we aim to describe the mechanisms by which LAB can fulfil the novel role of efficient cell factory for the production of functional biomolecules and food ingredients to enhance the quality of cereal-based beverages. LAB fermentation is a safe, economical, and traditional method of food preservation foremost, as well as having the additional benefits of flavor, texture, and nutrition amelioration. Additionally, LAB fermentation in known to render cereal-based foods and beverages safe, in a chemical-free, consumer-friendly manner, from an antinutrient and toxigenic perspective. Huge market opportunities and potential exist for food manufacturers who can provide the ideal functional beverage fulfilling consumer needs. Newly developed fermented cereal-based beverages must address markets globally including, high-nutrition markets (developing countries), lifestyle choice consumers (vegetarian, vegan, low-fat, low-salt, low-calorie), food-related non-communicable disease sufferers (cardiovascular disease, diabetes), and green label consumers (Western countries). To fulfil these recommendations, a suitable LAB starter culture and cereal-based raw materials must be developed. These strains would be suitable for the biopreservation of cereal beverages and, ideally, would be highly antifungal, anti-mycotoxigenic, mycotoxin-binding and proteolytic (neutralize toxic peptides and release flavor-contributing amino acids) with an ability to ferment cereals, whilst synthesizing oligosaccharides, thus presenting a major opportunity for the development of safe cereal-based prebiotic functional beverages to compete with and replace the existing dairy versions.

The Autism-Spectrum Quotient in university students: pattern of changes in its scores and associated factors

INTRODUCTION

Support to university students with autism spectrum disorders (ASD) is becoming increasingly important. To determine the validity of the Autism-Spectrum Quotient (AQ) for ASD screening of university students, we conducted longitudinal measurements of the AQ in a large sample of university students and investigated the possibility of changes in the AQ and associated factors.

METHODS

The AQ, University Personality Inventory (UPI), and the willingness of the students to be interviewed were determined at admission in students from four departments of Kochi University; the AQ was determined again in the second year. Changes in the AQ and associated factors were analyzed statistically.

RESULTS

The number of valid responses in the initial survey was 3427 (87.2%). The AQ was significantly higher in the group with high UPI scores (F = 156.08, P < 0.001). Of the 486 students interviewed at admission, 22 had suspected ASD. The sensitivity/specificity of the AQ for ASD was 81.8%/92.0%. A total of 319 (11.0%) students responded to the second-year survey, which revealed significant decrease of the AQ in the group with high AQ values at admission.

DISCUSSION

The AQ measured at admission was correlated with the UPI score, regardless of the sex or department; in the second survey, the scores decreased significantly in those with high AQ values at admission, suggesting that an unstable mental state can produce a temporary increase of the AQ scores.

Autism spectrum disorders--are they really epidemic?

AIM

The aim of this paper is to report on how different external methodological factors influence estimates of ASD prevalence.

METHODS

PubMed searches was conducted using the search terms, "Autism", "Autistic Disorder", "Autism Spectrum Disorders", "Asperger", "Prevalence" and "epidemiology", in combination. In total 49 studies were included. We also performed a manual search for and reviewed related articles referenced in the original articles.

RESULTS

The reported prevalence rates of ASD vary widely, and so do the methodology used in the studies.

CONCLUSION

There are reasons to argue that the methods used in some studies cause the high prevalence rates reported recently.

Association between autistic traits and social anxiety among Japanese university students

Background: Symptom overlap between autism spectrum disorders (ASD) and social anxiety disorder has been reported. However, few reports exist on the associations between autistic traits and social anxiety in young adults.

Methods: Autistic traits and social anxiety were assessed using the Autism-Spectrum Quotient (AQ) and the Liebowitz Social Anxiety Scale (LSAS), respectively. The survey was performed as part of the student health check-up at admission to our school, Kochi University. The relationship between the AO and LSAS scores were analyzed.

Results: In all, 1479 students (77.2%) completed both the questionnaires. The overall AQ score was significantly related to the score on the Japanese version of the LSAS (LSAS-J) (Spearman’s correlation coefficient; 0.46, p<0.001). The group of students with AQ≥33 had significantly higher total and subscale scores on the LSAS-J as compared to the group with AQ<33, while the group with LSAS-J≥44 showed significantly higher scores on all the subscales of the AQ, except “Attention to detail,” as compared to the group with LSAS-J<44.

Conclusions: The results suggest that both students diagnosed as having ASD and those with autistic traits may experience anxiety symptoms. The score for “Attention to detail” on the AQ, which was not related to the presence of social anxiety, may be useful in discriminating between autistic traits and social anxiety.

Prenatal and perinatal analgesic exposure and autism: an ecological link

BACKGROUND

Autism and Autism Spectrum Disorder (ASD) are complex neurodevelopmental disorders. Susceptibility is believed to be the interaction of genetic heritability and environmental factors. The synchronous rises in autism/ASD prevalence and paracetamol (acetaminophen) use, as well as biologic plausibility have led to the hypothesis that paracetamol exposure may increase autism/ASD risk.

METHODS

To explore the relationship of antenatal paracetamol exposure to ASD, population weighted average autism prevalence rates and paracetamol usage rates were compared. To explore the relationship of early neonatal paracetamol exposure to autism/ASD, population weighted average male autism prevalence rates for all available countries and U.S. states were compared to male circumcision rates - a procedure for which paracetamol has been widely prescribed since the mid-1990s. Prevalence studies were extracted from the U.S. Centers for Disease Control and Prevention Summary of Autism/ASD Prevalence Studies database. Maternal paracetamol usage and circumcision rates were identified by searches on Pub Med.

RESULTS

Using all available country-level data (n = 8) for the period 1984 to 2005, prenatal use of paracetamol was correlated with autism/ASD prevalence (r = 0.80). For studies including boys born after 1995, there was a strong correlation between country-level (n = 9) autism/ASD prevalence in males and a country's circumcision rate (r = 0.98). A very similar pattern was seen among U.S. states and when comparing the 3 main racial/ethnic groups in the U.S. The country-level correlation between autism/ASD prevalence in males and paracetamol was considerably weaker before 1995 when the drug became widely used during circumcision.

CONCLUSIONS

This ecological analysis identified country-level correlations between indicators of prenatal and perinatal paracetamol exposure and autism/ASD. State level correlation was also identified for the indicator of perinatal paracetamol exposure and autism/ASD. Like all ecological analyses, these data cannot provide strong evidence of causality. However, biologic plausibility is provided by a growing body of experimental and clinical evidence linking paracetamol metabolism to pathways shown to be important in autism and related developmental abnormalities. Taken together, these ecological findings and mechanistic evidence suggest the need for formal study of the role of paracetamol in autism.

Global prevalence of autism and other pervasive developmental disorders

We provide a systematic review of epidemiological surveys of autistic disorder and pervasive developmental disorders (PDDs) worldwide. A secondary aim was to consider the possible impact of geographic, cultural/ethnic, and socioeconomic factors on prevalence estimates and on clinical presentation of PDD. Based on the evidence reviewed, the median of prevalence estimates of autism spectrum disorders was 62/10 000. While existing estimates are variable, the evidence reviewed does not support differences in PDD prevalence by geographic region nor of a strong impact of ethnic/cultural or socioeconomic factors. However, power to detect such effects is seriously limited in existing data sets, particularly in low-income countries. While it is clear that prevalence estimates have increased over time and these vary in different neighboring and distant regions, these findings most likely represent broadening of the diagnostic concets, diagnostic switching from other developmental disabilities to PDD, service availability, and awareness of autistic spectrum disorders in both the lay and professional public. The lack of evidence from the majority of the world's population suggests a critical need for further research and capacity building in low- and middle-income countries.

Nosology and epidemiology in autism: classification counts

Since its initial description by Kanner in 1943, the criteria by which a diagnosis of autism or autism-like disorders was made--and their alleged etiologies portrayed--have undergone manifold changes, from a psychiatric disorder engendered by "refridgerator" parents to a neurodevelopmental disability produced in the main by genetic abnormalities. In addition, the behavioral characterization of autism has also entered the public consciousness and professional domains increasingly in the past 30 years, the effects of which we are continually coming to terms. A diagnosis of autism that once seemed quite unusual is now considered almost epidemic. Increasing numbers of individuals diagnosed with autism and related pervasive developmental disabilities will, in turn, affect the calculated prevalence of the disorder. In this essay, I attempt to account for the increasing prevalence of autism and autism-related disorders by examining its changing criteria, the individuals and instruments used to make the diagnosis, the reliability and validity of same, and the sample sizes and other aspects of the methodology needed to make an accurate estimate of its prevalence.

Autism spectrum disorders--a genetics review

Autism is an etiologically and clinically heterogeneous group of disorders, diagnosed solely by the complex behavioral phenotype. On the basis of the high-heritability index, geneticists are confident that autism will be the first behavioral disorder for which the genetic basis can be well established. Although it was initially assumed that major genome-wide and candidate gene association studies would lead most directly to common autism genes, progress has been slow. Rather, most discoveries have come from studies of known genetic disorders associated with the behavioral phenotype. New technology, especially array chromosomal genomic hybridization, has both increased the identification of putative autism genes and raised to approximately 25%, the percentage of children for whom an autism-related genetic change can be identified. Incorporating clinical geneticists into the diagnostic and autism research arenas is vital to the field. Interpreting this new technology and deciphering autism's genetic montage require the skill set of the clinical geneticist including knowing how to acquire and interpret family pedigrees, how to analyze complex morphologic, neurologic, and medical phenotypes, sorting out heterogeneity, developing rational genetic models, and designing studies. The current emphasis on deciphering autism spectrum disorders has accelerated the field of neuroscience and demonstrated the necessity of multidisciplinary research that must include clinical geneticists both in the clinics and in the design and implementation of basic, clinical, and translational research.

The association of autism diagnosis with socioeconomic status

Background: In 2007 the Centers for Disease Control and Prevention (CDC) reported a higher prevalence of autism spectrum disorder (ASD) in New Jersey, one of the wealthiest states in the United States, than in other surveillance regions.

Objective: To examine the association of socioeconomic status (SES) with ASD prevalence.

Methods: Information on eight-year-olds with ASD from four counties was abstracted from school and medical records. US Census 2000 provided population and median household income data.

Results: 586 children with ASD were identified: autism prevalence was 10.2/1000, higher in boys than girls (16 vs. 4/1000); higher in white and Asian non-Hispanics than in black non-Hispanics and Hispanics (12.5, 14.0, 9.0, and 8.5/1000, respectively); and higher (17.2/1000 (95% CI 14.0–21.1)) in tracts with median income >US$90,000 than in tracts with median income ≤US$30,000 (7.1 (95% CI 5.7–8.9)). Number of professional evaluations was higher, and age at diagnosis younger, in higher income tracts ( p < .001), but both measures spanned a wide overlapping range in all SES levels. In multivariable models race/ethnicity did not predict ASD, but the prevalence ratio was 2.2 (95% CI 1.5–3.1) when comparing highest with lowest income tracts.

Conclusions: In the US state of New Jersey, ASD prevalence is higher in wealthier census tracts, perhaps due to differential access to pediatric and developmental services.

Prevalence of autism according to maternal immigrant status and ethnic origin

OBJECTIVE

To examine the rates of autism separately according to maternal immigrant status and ethnic origin in respect to the vitamin D insufficiency hypothesis.

METHOD

Articles were identified by electronic searches. Studies were selected when they analysed autism rates according to maternal immigrant status and/or ethnic origin using multivariate techniques.

RESULTS

This review gave further support to the association between maternal immigrant status and an increased risk of autism. The relationship with ethnic origin was more complex. Although the crude rates did not differ, multivariate analyses taking into account confounding factors found that black ethnicity was associated with an increased risk for autism. The risk was highly significant when considering the strict definition of autistic disorders as opposed to the large definition of other pervasive developmental disorders. The risk was also very significant for autism associated with mental retardation.

CONCLUSION

These results are consistent with the maternal vitamin D insufficiency hypothesis. Neurobiological studies are warranted to document the effect of maternal vitamin D insufficiency during pregnancy on the foetal brain and the window of vulnerability. This review stresses the importance of monitoring vitamin D levels in pregnant women, especially those who are immigrant, dark-skinned or veiled, and the urgency of randomized controlled trials.

Timing of increased autistic disorder cumulative incidence

Autistic disorder (AD) is a severe neurodevelopmental disorder typically identified in early childhood. Both genetic and environmental factors are implicated in its etiology. The number of individuals identified as having autism has increased dramatically in recent years, but whether some proportion of this increase is real is unknown. If real, susceptible populations may have exposure to controllable exogenous stressors. Using literature AD data from long-term (approximately 10-year) studies, we determined cumulative incidence of AD for each cohort within each study. These data for each study were examined for a changepoint year in which the AD cumulative incidence first increased. We used data sets from Denmark, California, Japan, and a worldwide composite of studies. In the Danish, California, and worldwide data sets, we found that an increase in AD cumulative incidence began about 1988-1989. The Japanese study (1988-1996) had AD cumulative incidence increasing continuously, and no changepoint year could be calculated. Although the debate about the nature of increasing autism continues, the potential for this increase to be real and involve exogenous environmental stressors exists. The timing of an increase in autism incidence may help in screening for potential candidate environmental stressors.

Epidemiology of pervasive developmental disorders

This article reviews the results of 43 studies published since 1966 that provided estimates for the prevalence of pervasive developmental disorders (PDDs), including autistic disorder, Asperger disorder, PDD not otherwise specified, and childhood disintegrative disorder. The prevalence of autistic disorder has increased in recent surveys and current estimates of prevalence are around 20/10,000, whereas the prevalence for PDD not otherwise specified is around 30/10,000 in recent surveys. Prevalence of Asperger disorder is much lower than that for autistic disorder and childhood disintegrative disorder is a very rare disorder with a prevalence of about 2/100,000. Combined all together, recent studies that have examined the whole spectrum of PDDs have consistently provided estimates in the 60-70/10,000 range, making PDD one of the most frequent childhood neurodevelopmental disorders. The meaning of the increase in prevalence in recent decades is reviewed. There is evidence that the broadening of the concept, the expansion of diagnostic criteria, the development of services, and improved awareness of the condition have played a major role in explaining this increase, although it cannot be ruled out that other factors might have also contributed to that trend.

Quantitative assessment of autism symptom-related traits in probands and parents: Broader Phenotype Autism Symptom Scale

Autism susceptibility genes likely have effects on continuously distributed autism-related traits, yet few measures of such traits exist. The Broader Phenotype Autism Symptom Scale (BPASS), developed for use with affected children and family members, measures social motivation, social expressiveness, conversational skills, and flexibility. Based on 201 multiplex families, psychometric data on the BPASS are reported. Adequate inter-rater reliability and internal consistency were found. Parents had lower BPASS scores than affected children, after controlling for IQ. Parents and affected children showed overlapping distributions suggesting the BPASS captured variability in traits across groups. BPASS scores were not correlated with ethnicity or parent education; however, some domains were correlated with IQ. The BPASS holds promise as a quantitative phenotypic assessment for genetic studies.

Lack of association between Rh status, Rh immune globulin in pregnancy and autism

Though causes of autism are considered largely genetic, considerable concern remains that exposure to Rh immune globulin (RhIg), which until 2001 in the United States contained the preservative thimerosal, can cause autism. To determine whether mothers of children with autism are more likely to be Rh negative (Rh(-)) or to have received RhIg preserved with thimerosal, which is 49.6% ethyl mercury, we surveyed families of children with an autism spectrum disorder (ASD) ascertained through a University-based autism clinic considered free of ascertainment biases related to type of autism or severity. Between 2004 and 2006, 305 mothers of 321 children with an ASD agreed to participate in a telephone interview. Analysis of complete records including the blood group status and RhIg exposure of 214 families showed that Rh(-) status is no higher in mothers of children with autism than in the general population, exposure to antepartum RhIg, preserved with thimerosal is no higher for children with autism and pregnancies are no more likely to be Rh incompatible. This was also true for autism subgroups defined by behavioral phenotype, gender, IQ, regressive onset, head circumference, dysmorphology, birth status, essential, or complex phenotype. These findings support the consensus that exposure to ethylmercury in thimerosal is not the cause of the increased prevalence of autism. These data are important not only for parents in this country but also for the international health community where thimerosal continues to be used to preserve multi-dose vials which in turn makes vaccines affordable.

Autism in the Faroe Islands. An Epidemiological Study

The Faroe Islands are considered to be a genetic isolate. This population study of the prevalence of autism sought to identify a representative cohort for future genetic studies. In 2002 all schools were screened for autism spectrum disorders. The target population were all children born in 1985 through 1994 and living in the Faroe Islands on December 31, 2002. Children who screened positive for autism characteristics were examined using the Diagnostic Interview for Social and Communication Disorders (DISCO). Of the children aged 8 through 17 years, 0.56% had childhood autism, Asperger syndrome or atypical autism. The male:female ratio was just under 6:1. The prevalence of autism in the Faroe Islands was very similar to that reported from many western countries.

Sociodemographic Risk Factors for Autism in a US Metropolitan Area

The present study examined the association between autism and sociodemographic factors, overall and in subgroups of children with autism with and without mental retardation (Autism/MR and Autism/No MR, respectively); the association was further examined in subanalyses by child's source of ascertainment to assess the presence of ascertainment bias. In the main analyses, one marker of higher social class (higher median family income) was significantly associated with autism overall. Both markers of higher social class (higher maternal education and higher median family income) were significantly associated with autism/no MR, but not associated with autism/MR. In the subanalyses, associations with social class varied by ascertainment source. Future studies should consider phenotypic subgroups of children with autism and must consider potential ascertainment bias.

Assessing Need for Social Support in Parents of Children with Autism and Down Syndrome

Parents of children with autism frequently turn to the service delivery system to access supports designed to help adapt to the challenges of having a child with a life-long impairment. Although studies have suggested various supports and coping strategies that are effective for adapting, few studies have examined parents' own perceptions of needs, and whether parents felt their needs were being met. In the present study the Family Needs Questionnaire (FNQ; Waaland et al., 1993) was modified to address needs for children with developmental disorders. A sample of fifty-six parents of children with autism and a comparison group of thirty-two parents of children with Down syndrome completed the FNQ. The groups did not differ significantly on the number of important needs reported nor the number of important needs being met. However, the two groups differed in the types of supports they most frequently endorsed as Important or Unmet.

Verbal communication outcomes in children with autism after in-home father training

BACKGROUND

This retrospective study examined the efficacy of in-home father training on the communicative outcomes of children with autism. The in-home training consisted of two components: (1) expectant waiting; and (2) imitation with animation.

METHODS

Efficacy of parent training was examined by measuring the ratio of utterances produced by the parents to the utterances produced by the children and the number of verbal imitation by the parents. Outcomes of the children's verbal production were examined by measuring the number of (1) single word utterances; (2) different words produced; and (3) verbal response to questions.

RESULTS

Following training there was a decrease in the ratio of parent to child utterances and an increase in (1) the use of imitation by the parents; and (2) the number of single words and different words produced by the children.

DISCUSSION

Results of this study suggested that the parents had learned to wait for their children to communicate verbally during communicative interactions and to interact more efficiently with their children by using verbal imitation. Overall, the results of this study support the efficacy of parent training that focuses on promotion of social reciprocity, and have important implications for clinicians and future research.

Incidence of autism spectrum disorders: changes over time and their meaning

AIM

Several reviews have noted a huge increase in the rate of diagnosed autism spectrum disorders. The main aims of this paper are: 1) to use published empirical findings to consider whether the rise reflects a true increase in incidence, as distinct from the consequences of better ascertainment and a broadening of the diagnostic concept; and 2) to consider how epidemiological data may be used to test hypotheses about possible causal influences, using MMR and thimerosal as examples.

METHODS

Search of the literature for studies with a large epidemiological base population, systematic standardized screening, a focus on an age group for which diagnostic assessments are reliable and valid, and diagnosis by trained professionals using high-quality research assessments. Also, search of a broader literature to consider the evidence from all epidemiological studies with respect to the hypothesized causal effect of MMR and thimerosal on autism spectrum disorders.

RESULTS

The true incidence of autism spectrum disorders is likely to be within the range of 30-60 cases per 10 000, a huge increase over the original estimate 40 years ago of 4 per 10000. The increase is largely a consequence of improved ascertainment and a considerable broadening of the diagnostic concept. However, a true risk due to some, as yet to be identified, environmental risk factor cannot be ruled out. There is no support for the hypothesis for a role of either MMR or thimerosal in causation, but the evidence on the latter is more limited.

CONCLUSION

Progress in testing environmental risk hypotheses will require the integration of epidemiological and biological studies.

What's going on? The question of time trends in autism

Increases in the reported prevalence of autism and autistic spectrum disorders in recent years have fueled concern over possible environmental causes. The author reviews the available survey literature and finds evidence of large increases in prevalence in both the United States and the United Kingdom that cannot be explained by changes in diagnostic criteria or improvements in case ascertainment. Incomplete ascertainment of autism cases in young child populations is the largest source of predictable bias in prevalence surveys; however, this bias has, if anything, worked against the detection of an upward trend in recent surveys. Comparison of autism rates by year of birth for specific geographies provides the strongest basis for trend assessment. Such comparisons show large recent increases in rates of autism and autistic spectrum disorders in both the U.S. and the U.K. Reported rates of autism in the United States increased from < 3 per 10,000 children in the 1970s to > 30 per 10,000 children in the 1990s, a 10-fold increase. In the United Kingdom, autism rates rose from < 10 per 10,000 in the 1980s to roughly 30 per 10,000 in the 1990s. Reported rates for the full spectrum of autistic disorders rose from the 5 to 10 per 10,000 range to the 50 to 80 per 10,000 range in the two countries. A precautionary approach suggests that the rising incidence of autism should be a matter of urgent public concern.

Prevalence of autism in a US metropolitan area

CONTEXT

Concern has been raised about possible increases in the prevalence of autism. However, few population-based studies have been conducted in the United States.

OBJECTIVES

To determine the prevalence of autism among children in a major US metropolitan area and to describe characteristics of the study population.

DESIGN, SETTING, AND POPULATION

Study of the prevalence of autism among children aged 3 to 10 years in the 5 counties of metropolitan Atlanta, Ga, in 1996. Cases were identified through screening and abstracting records at multiple medical and educational sources, with case status determined by expert review.

MAIN OUTCOME MEASURES

Autism prevalence by demographic factors, levels of cognitive functioning, previous autism diagnoses, special education eligibility categories, and sources of identification.

RESULTS

A total of 987 children displayed behaviors consistent with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for autistic disorder, pervasive developmental disorder-not otherwise specified, or Asperger disorder. The prevalence for autism was 3.4 per 1000 (95% confidence interval [CI], 3.2-3.6) (male-female ratio, 4:1). Overall, the prevalence was comparable for black and white children (black, 3.4 per 1000 [95% CI, 3.0-3.7] and white, 3.4 per 1000 [95% CI, 3.2-3.7]). Sixty-eight percent of children with IQ or developmental test results (N = 880) had cognitive impairment. As severity of cognitive impairment increased from mild to profound, the male-female ratio decreased from 4.4 to 1.3. Forty percent of children with autism were identified only at educational sources. Schools were the most important source for information on black children, children of younger mothers, and children of mothers with less than 12 years of education.

CONCLUSION

The rate of autism found in this study was higher than the rates from studies conducted in the United States during the 1980s and early 1990s, but it was consistent with those of more recent studies.

The epidemiology of autistic spectrum disorders: is the prevalence rising?

For decades after Kanner's original paper on the subject was published in 1943, autism was generally considered to be a rare condition with a prevalence of around 2-4 per 10,000 children. Then, studies carried out in the late 1990s and the present century reported annual rises in incidence of autism in pre-school children, based on age of diagnosis, and increases in the age-specific prevalence rates in children. Prevalence rates of up to 60 per 10,000 for autism and even more for the whole autistic spectrum were reported. Reasons for these increases are discussed. They include changes in diagnostic criteria, development of the concept of the wide autistic spectrum, different methods used in studies, growing awareness and knowledge among parents and professional workers and the development of specialist services, as well as the possibility of a true increase in numbers. Various environmental causes for a genuine rise in incidence have been suggested, including the triple vaccine for measles, mumps and rubella (MMR]. Not one of the possible environmental causes, including MMR, has been confirmed by independent scientific investigation, whereas there is strong evidence that complex genetic factors play a major role in etiology. The evidence suggests that the majority, if not all, of the reported rise in incidence and prevalence is due to changes in diagnostic criteria and increasing awareness and recognition of autistic spectrum disorders. Whether there is also a genuine rise in incidence remains an open question.

Prevalence of autism in a United States population: the Brick Township, New Jersey, investigation

OBJECTIVE

This study determined the prevalence of autism for a defined community, Brick Township, New Jersey, using current diagnostic and epidemiologic methods.

METHODS

The target population was children who were 3 to 10 years of age in 1998, who were residents of Brick Township at any point during that year, and who had an autism spectrum disorder. Autism spectrum disorder was defined as autistic disorder, pervasive developmental disorder-not otherwise specified (PDD-NOS), and Asperger disorder. The study used 4 sources for active case finding: special education records, records from local clinicians providing diagnosis or treatment for developmental or behavioral disabilities, lists of children from community parent groups, and families who volunteered for participation in the study in response to media attention. The autism diagnosis was verified (or ruled out) for 71% of the children through clinical assessment. The assessment included medical and developmental history, physical and neurologic evaluation, assessment of intellectual and behavioral functioning, and administration of the Autism Diagnostic Observation Schedule-Generic.

RESULTS

The prevalence of all autism spectrum disorders combined was 6.7 cases per 1000 children. The prevalence for children whose condition met full diagnostic criteria for autistic disorder was 4.0 cases per 1000 children, and the prevalence for PDD-NOS and Asperger disorder was 2.7 cases per 1000 children. Characteristics of children with autism in this study were similar to those in previous studies of autism.

CONCLUSIONS

The prevalence of autism in Brick Township seems to be higher than that in other studies, particularly studies conducted in the United States, but within the range of a few recent studies in smaller populations that used more thorough case-finding methods.

Measles-mumps-rubella vaccine and autistic spectrum disorder: report from the New Challenges in Childhood Immunizations Conference convened in Oak Brook, Illinois, June 12-13, 2000

BACKGROUND

Parents and physicians are understandably concerned about the causes and treatment of autism, a devastating disease that affects the entire family. Although much has been learned about autism, there are many gaps in our knowledge about what causes the disorder and how it can be prevented. Autistic symptoms occur along a spectrum, often referred to as autistic spectrum disorder (ASD). Concern has been raised about a possible association between measles-mumps-rubella (MMR) vaccine and inflammatory bowel disease (IBD) and ASD, especially autism with regression. Also, increased requests for educational services related to ASD have raised concerns about possible increases in the incidence of ASD.

METHODS

On June 12-13, 2000, the American Academy of Pediatrics (AAP) convened a conference titled "New Challenges in Childhood Immunizations" in Oak Brook, Illinois. At this conference, parents, practitioners, and scientists presented information and research on MMR vaccine and ASD. Attendees included representatives from select AAP committees and sections as well as federal and other organizations that address related issues. The multidisciplinary panel of experts reviewed data on what is known about the pathogenesis, epidemiology, and genetics of ASD and the available data on hypothesized associations with IBD, measles, and MMR vaccine. Supplemental information was requested from authors who have proposed the hypotheses and other experts in relevant areas.

RESULTS

Autism is a complex disorder of uncertain and probably multiple etiologies. Genetic predisposition to ASD may involve as many as 10 genes. Many experts believe that the abnormal brain development in autism occurs before 30 weeks' gestation in most instances. In utero rubella is a known cause of autism. Animal model data support the biologic plausibility that exposure to yet unrecognized infectious or other environmental agents could cause ASD. Several factors may contribute to apparent increases in incidence of ASD in recent years. Most data indicate increased recognition and reporting as primary factors, but the epidemiologic data are insufficient to determine if there has been a true increase in the incidence of ASD. Increased reporting of ASD in recent years has occurred long after the introduction of MMR vaccine in the United States in 1971 and widespread use of this vaccine in the 1970s for routine immunization of children at 12 to 15 months of age. Appropriate detailed studies are needed to define the true incidence and prevalence of ASD. Epidemiologic studies in Europe indicate no association between MMR vaccine and ASD. Some children with ASD have gastrointestinal symptoms, but an increased rate of any specific gastrointestinal disorder in children with ASD has not been established. Studies to detect evidence of measles virus in intestinal tissue specimens from patients with IBD or autism with gastrointestinal symptoms have not used uniform techniques. Several laboratories have found no evidence of measles viruses in tissue specimens from patients with IBD, but 2 groups have found evidence of measles virus using different techniques. A group that found evidence of measles virus in affected tissue specimens from patients with IBD has also reported detecting portions of measles virus in peripheral blood lymphocytes and intestinal tissue specimens from patients with autism and gastrointestinal disorders. Finding a portion of a virus using molecular techniques does not constitute evidence for a causal relationship, because some viruses persist in unaffected hosts. Additional controlled studies in several laboratories are needed to determine if portions of measles virus persist in intestinal and other tissues of people with and without gastrointestinal disease and/or ASD.

CONCLUSIONS

Although the possible association with MMR vaccine has received much public and political attention and there are many who have derived their own conclusions based on personal experiences, the available evidence does not support the hypothesis that MMR vaccine causes autism or associated disorders or IBD. Separate administration of measles, mumps, and rubella vaccines to children provides no benefit over administration of the combination MMR vaccine and would result in delayed or missed immunizations. Pediatricians need to work with families to ensure that children are protected early in the second year of life from these preventable diseases. Continued scientific efforts need to be directed to the identification of the causes of ASD.

American Academy of Pediatrics: The pediatrician's role in the diagnosis and management of autistic spectrum disorder in children

Primary care physicians have the opportunity, especially within the context of the medical home, to be the first point of contact when parents have concerns about their child's development or behavior. The goal of this policy statement is to help the pediatrician recognize the early symptoms of autism and participate in its diagnosis and management. This statement and the accompanying technical report will serve to familiarize the pediatrician with currently accepted criteria defining the spectrum of autism, strategies used in making a diagnosis, and conventional and alternative interventions.

Technical report: the pediatrician's role in the diagnosis and management of autistic spectrum disorder in children

Autism and its milder variants are not rare. Most pediatricians will have the opportunity to provide a medical home for a child with autism. This technical report serves to complement and expand on the information in the accompanying policy statement to increase the pediatrician's fund of knowledge and comfort level in caring for children with autism. In so doing, it is anticipated that earlier diagnosis and referral for appropriate intervention will be possible and that this will, in turn, have a positive effect on long-term outcomes for children with autism and their families.

A screening instrument for autism at 18 months of age: a 6-year follow-up study

OBJECTIVES

A population of 16,235 children aged 18 months was screened using the Checklist for Autism in Toddlers (CHAT) to identify childhood autism (CA). Two further screening procedures were conducted at age 3 and 5 years. The population was followed up at age 7 years in order to establish the sensitivity, specificity, and positive predictive value of the instrument.

METHOD

A brief checklist assessing joint attention and pretend play behaviors was administered by primary health care practitioners when the children were 18 months old. Follow-up methods included screening through parents and health practitioners and checking medical and educational records.

RESULTS

Nineteen cases of CA were successfully identified by the CHAT at 18 months. At follow-up a total of 50 cases of CA were identified via all surveillance methods. Thus, the CHAT has a sensitivity of 38% and a specificity of 98% for identifying CA. The positive predictive value of the instrument was maximized by concentration on the highest-risk group. Repeated screening 1 month later increased the positive predictive value to 75% for identification of CA but reduced the sensitivity to 20%, although the specificity was close to 100%. The screen also identified cases of pervasive developmental disorder as well as children with language and other developmental disorders.

CONCLUSIONS

The CHAT can be used to identify cases of autism and related pervasive developmental disorders at 18 months of age. It is emphasized that the CHAT is not a diagnostic instrument but can identify potential cases of autism spectrum disorders for a full diagnostic assessment.

Autism--an evolving concept

BACKGROUND

The rapid increase in research endeavour has not kept pace with the advent of well-publicized theories and treatments for autism.

AIMS

To explore some of the newer developments in biological research into autism.

METHOD

A review of recent publications and presentations.

RESULTS

The concept is shifting from the narrow perception of aloof autism, described by Kanner, to a wider one that includes a spectrum extending to a broader, subclinical phenotype. The genetic basis has been established; now we need to discover the location and interaction of the relevant sites. There is considerable interest in the bowel as a pathogenetic agent, particularly in the effects of exogenous opioids and multiple viral infection (the latter posing a public health problem). Also of concern is the role of (potentially treatable) epilepsy, analogous to the Laudau-Kleffner syndrome.

CONCLUSIONS

In the absence of a cure, the implementation of ideas will continue to outstrip factual evidence. Clinicians are challenged by the availability of information (and misinformation), particularly on the internet.

Autism: not an extremely rare disorder

OBJECTIVE

To study autism over time in order to ascertain whether there has been an increase in its prevalence in recent years.

METHOD

All English language papers on the prevalence of autism were reviewed. Ten of the studies retrieved were not used in the final analysis because they did not meet full criteria for inclusion in the review. The remaining 20 studies, published between 1966 and 1997, were subdivided into US studies (n=2) and non-US studies (n=18), and the latter group was subdivided into four 8-year periods.

RESULTS

The early studies yielded prevalence rates of under 0.5 in 1000 children, whereas the later ones showed a mean rate of about 1 in 1000. There was a marked difference in prevalence rates between those studies that included some children born before 1970 (low rates) and those that included only children born in 1970 and after (high rates). This is probably due to the lower rates obtained by use of criteria strictly based on Kanner's description of his syndrome. The US studies reported atypically low rates. There was a highly significant estimated increase with calendar year in the non-US studies (3.8% per year).

CONCLUSION

It is concluded that autism is considerably more common than was previously believed. The possible reasons for the higher reported rates are discussed.

Neuropsychiatric disorders

Neuropsychiatric disorders of childhood include autism spectrum disorders, disorders comprising attention deficits (attention-deficit-hyperactivity disorder and deficits in attention, motor control and perception), tics (motor or vocal, or both), and obsessions and compulsions (obsessive-compulsive disorder). They affect a small proportion of the child population. They can now reliably be diagnosed, and are valid and clinically meaningful conditions. Effective interventions are available for most of these disorders.