Prevalence and characteristics of autism spectrum disorders in the ALSPAC cohort

Developmental Medicine & Child Neurology (Impact Factor: 3.51). 08/2008; 50(9):672 - 677. DOI: 10.1111/j.1469-8749.2008.03042.x


The aim of this study was to determine the prevalence of autistic spectrum disorder (ASD) within a large representative population sample: the Avon Longitudinal Study of Parents and Children (ALSPAC). Cases of ASD were identified from the clinical notes of children in the ALSPAC with a suspected developmental disorder and from the Pupil Level Annual Schools Census (PLASC) for England in 2003. Seventy-one cases of ASD diagnosed after a multidisciplinary assessment were identified from health records. There were an additional 15 cases from PLASC data in which ASD was mentioned as a principal difficulty, thus giving a total of 86 children diagnosed by the age of 11 years. Prevalence of ASD per 10 000 population at 11 years was 51.1 for those with a multi-professional diagnosis, and 61.9 if cases from education were included, made up of 21.6 for childhood autism, 10.8 for atypical autism, 16.6 for Asperger syndrome, and 13.0 for unspecified ASD. The male:female ratio was 6.8:1. Median age at diagnosis ranged from 45 months in childhood autism to 116 months in Asperger syndrome. A comorbid developmental disorder was recorded in 33.8% of cases, including learning disability† in 14.7%, epilepsy in 10.3%, and mixed developmental disorder in 4.4%. We conclude that the prevalence of ASD diagnosed at 11 years in a UK representative population-based sample is at least 51.1/10 000.

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    • "diagnostic methods or any of these in combination. In most ASD diagnoses, a skewed gender ratio has been found, with increased prevalence in males at a ratio of 4:1 (males:females) or even higher (Scott et al., 2002; Williams et al., 2008). One hypothesis that takes into account the gender effect and the cognitive style of ASD is the 'extreme male brain theory'. "
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    ABSTRACT: Autism spectrum disorders (ASD) are a heterogeneous group of disorders which have complex behavioural phenotypes. Although ASD is a highly heritable neuropsychiatric disorder, genetic research alone has not provided a profound understanding of the underlying causes. Recent developments using biochemical tools such as transcriptomics, proteomics and cellular models, will pave the way to gain new insights into the underlying pathological pathways. This review addresses the state-of-the-art in the search for molecular biomarkers for ASD. In particular, the most important findings in the biochemical field are highlighted and the need for establishing streamlined interaction between behavioural studies, genetics and proteomics is stressed. Eventually, these approaches will lead to suitable translational ASD models and, therefore, a better disease understanding which may facilitate novel drug discovery efforts in this challenging field.
    Full-text · Article · Nov 2013 · The International Journal of Neuropsychopharmacology
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    • "Within ALSPAC there is a very small proportion of children with ASD, who were either identified from community paediatric records (National Health Service) or from Education Service databases for the region [36]. Specifically, there were 86 children with ASD at the age of 11 years (prevalence: 62 per 10,000 children). "
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    ABSTRACT: Social communication difficulties represent an autistic trait that is highly heritable and persistent during the course of development. However, little is known about the underlying genetic architecture of this phenotype. We performed a genome-wide association study on parent-reported social communication problems using items of the children's communication checklist (age 10 to 11 years) studying single and/or joint marker effects. Analyses were conducted in a large UK population-based birth cohort (Avon Longitudinal Study of Parents and their Children, ALSPAC, N = 5,584) and followed-up within a sample of children with comparable measures from Western Australia (RAINE, N = 1364). Two of our seven independent top signals (P-discovery <1.0E-05) were replicated (0.009 < P-replication <=0.02) within RAINE and suggested evidence for association at 6p22.1 (rs9257616, meta-P = 2.5E-07) and 14q22.1 (rs2352908, meta-P = 1.1E-06). The signal at 6p22.1 was identified within the olfactory receptor gene cluster within the broader major histocompatibility complex (MHC) region. The strongest candidate locus within this genomic area was TRIM27. This gene encodes an ubiquitin E3 ligase, which is an interaction partner of methyl-CpG-binding domain (MBD) proteins, such as MBD3 and MBD4, and rare protein-coding mutations within MBD3 and MBD4 have been linked to autism. The signal at 14q22.1 was found within a gene-poor region.Single-variant findings were complemented by estimations of the narrow-sense heritability in ALSPAC suggesting that approximately a fifth of the phenotypic variance in social communication traits is accounted for by joint additive effects of genotyped single nucleotide polymorphisms throughout the genome (h2(SE) = 0.18(0.066), P = 0.0027). Overall, our study provides both joint and single-SNP-based evidence for the contribution of common polymorphisms to variation in social communication phenotypes.
    Full-text · Article · Sep 2013 · Molecular Autism
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    • "years on average, which was probably too short to identify all cases, as disorders such as Asperger's syndrome are often diagnosed later. Studies conducted in the UK, in which children with Asperger's syndrome have been diagnosed in the 1990s and 2000s have suggested that the median age at diagnosis is almost 10 years (Williams et al., 2008) or the mean age around 7 years depending on the year of diagnosis (Latif and Williams, 2007). The only cohort study in which a significant positive association between IVF and ASDs has been found [odds ratio (OR): 1.68, 95% confidence interval (CI): 1.11 –2.53] was based on a Finnish cohort (Klemetti et al., 2006) but the definition of the outcome was even less precise than in the previously mentioned studies. "
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    ABSTRACT: STUDY QUESTION: Does IVF increase the risk of autism spectrum disorders (ASDs)? SUMMARY ANSWER: No association between IVF and ASDs or any of its subtypes was found in this sample. WHAT IS KNOWN ALREADY: Certain prenatal factors may increase the risk of ASDs. Studies on the association between IVF and ASDs have shown inconsistent results. IVF is known to increase the risk of perinatal problems but many of them are related to multiple pregnancies. STUDY DESIGN, SIZE, DURATION: This case-control study included 4164 autistic cases and 16 582 matched controls born in Finland in 1991-2005. The cases were diagnosed with ASDs by the year 2007. The maximum age at diagnosis was 16 years. PARTICIPANTS/MATERIALS, SETTING, METHODS: Four controls were matched to each case. For singletons the matching criteria were date of birth, place of birth, sex and residency in Finland. For twins the birth order within a twin pair was included as well. In the whole sample, there were 63 cases (1.51%) and 229 controls (1.38%) born after IVF. MAIN RESULTS AND THE ROLE OF CHANCE: No significant association was found between IVF and ASDs (adjusted odds ratio (OR): 0.9, 95% confidence interval (CI): 0.7-1.3) or its subtypes childhood autism (OR: 0.8, 95% CI: 0.4-1.5), Asperger's syndrome (OR: 0.9, 95% CI: 0.5-1.6) or other pervasive developmental disorder (OR: 1.0, 95% CI: 0.6-1.6). When only singletons were included, there was an association between IVF and Asperger's syndrome in an unadjusted analysis (OR: 2.0, 95% CI: 1.1-3.5) but this was not significant when adjusted for mother's socioeconomic status or parity. When the analyses were conducted separately for boys and girls, there was a significant association between IVF and Asperger's syndrome for boys in an unadjusted analysis (OR: 2.1, 95% CI: 1.2-3.7) but this was not significant in the final adjusted model. LIMITATIONS, REASONS FOR CAUTION: Information both on IVF and on ASDs was based on registers and it is possible that there is some misclassification. No information on different subtypes of IVF or other assisted reproduction techniques was available. Statistical power may have been insufficient. WIDER IMPLICATIONS OF THE FINDINGS: This study showed no increased risk of ASDs in children born after IVF but studies with larger sample sizes and information on different subtypes of IVF are needed to confirm the finding. STUDY FUNDING/COMPETING INTEREST(S): The study was supported by Autism Speaks, NIMH 1K02-MH65422 and NIEHS 1R01ES019004. There are no competing interests.
    Preview · Article · Jan 2013 · Human Reproduction
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