Glenys Dixon

Autism spectrum disorders in young children: effect of changes in diagnostic practices.

BACKGROUND It is unclear whether the increase in autism over the past two decades is a real increase or due to changes in diagnosis and ascertainment of autism spectrum disorders (ASDs), which include autism, Asperger syndrome and pervasive developmental disorder not otherwise specified (PDD-NOS). The aim of this study was to examine the trends in ASD over time in Western Australia (WA) and the possible effects and contribution of changes in diagnostic criteria, age at diagnosis, eligibility for service provision based on ASD diagnoses and changes in diagnostic practices. METHODS A population-based study was conducted among the cohort of children born in WA between 1983 and 1999 and diagnosed with ASD between the age of 2 and 8 years up to December 31, 2004. The trend in ASD diagnosis over the study period was assessed by investigating birth cohort and period effects, and examining whether these were modified by age of diagnosis. ASD diagnosis corresponding with changes in diagnostic criteria, funding and service provision over time were also investigated. A subgroup analysis of children aged <or=5 years was also conducted to examine trends in the incidence and age of diagnosis of ASD and intellectual disability (ID) and to investigate the role of changes in diagnostic practices. RESULTS The overall prevalence of ASD among children born between 1983 and 1999 and diagnosed by age 8 was 30 per 10,000 births with the prevalence of autism comprising 21 per 10,000 births. The prevalence of ASD increased by 11.9% per annum, from 8 cases per 10,000 births in 1983 to 46 cases per 10,000 births in 1999. The annual incidence of ASD, based on newly diagnosed ASD cases in each year from 1985 to 2002, increased over the study period. The increase in incidence of ASD appeared to coincide with changes in diagnostic criteria and availability of funding and services in WA, particularly for children aged <5 years. The age-specific rates of autism and PDD-NOS increased over time and the median age of diagnosis for autism decreased from 4 to 3 years of age throughout the 1990s. For children aged <or=5 years the incidence of ASD diagnosis increased significantly from 1992, with an average annual increase of 22%. Similar findings were found for autism. In the corresponding years the incidence of diagnosis of severe ID fell by 10% per annum and mild-moderate ID increased by 3% per annum. CONCLUSIONS The rise in incidence of all types of ASDs by year of diagnosis appears to be related to changes in diagnostic and service provision practices in WA. In children aged <or=5 years, diagnosis of severe ID decreased, but mild-moderate ID increased during the study period. A true increase in ASD cannot be ruled out.

Cerebral palsy following term newborn encephalopathy : a population-based study

Cerebral palsy (CP) can occur in term infants with or without preceding newborn encephalopathy. We compared the type and severity of CP and associated disability in these two groups. Participants from a population-based case-control study of term newborn encephalopathy were followed up for 6 years and linked to the Western Australian Cerebral Palsy Register. The remaining term infants with CP for the same period were also identified from the Cerebral Palsy Register. 13% of neonatal survivors of term newborn encephalopathy had CP, a rate of 116 per 1000 term live births. Overall, 24% of term infants with CP followed newborn encephalopathy. CP following newborn encephalopathy was more likely to: affect males (72% vs 56%); be severe (47% vs 25%); and be of spastic quadriplegia or dyskinetic types. Cognitive impairment was more common (75% vs 43%) and severe (41% vs 16%), as was epilepsy (53% vs 29%) in survivors of encephalopathy. These children were also more likely to: be non-verbal (47% vs 22%); have a severe composite disability score (47% vs 26%); and die between time of diagnosis of CP and age 6 years (5-year cumulative mortality 19% vs 5%). Children born at term who develop CP following newborn encephalopathy have a poorer prognosis than those with CP who were not encephalopathic in the first week of life.

Autism and intellectual disability are differentially related to sociodemographic background at birth.

Background Research findings investigating the sociodemographics of autism spectrum disorder (ASD) have been inconsistent and rarely considered the presence of intellectual disability (ID). Methods We used population data on Western Australian singletons born from 1984 to 1999 (n = 398,353) to examine the sociodemographic characteristics of children diagnosed with ASD with or without ID, or ID without ASD compared with non-affected children. Results The profiles for the four categories examined, mild-moderate ID, severe ID, ASD without ID and ASD with ID varied considerably and we often identified a gradient effect where the risk factors for mild-moderate ID and ASD without ID were at opposite extremes while those for ASD with ID were intermediary. This was demonstrated clearly with increased odds of ASD without ID amongst older mothers aged 35 years and over (odds ratio (OR) = 1.69 [CI: 1.18, 2.43]), first born infants (OR = 2.78; [CI: 1.67, 4.54]), male infants (OR = 6.57 [CI: 4.87, 8.87]) and increasing socioeconomic advantage. In contrast, mild-moderate ID was associated with younger mothers aged less than 20 years (OR = 1.88 [CI: 1.57, 2.25]), paternal age greater than 40 years (OR = 1.59 [CI: 1.36, 1.86]), Australian-born and Aboriginal mothers (OR = 1.60 [CI: 1.41, 1.82]), increasing birth order and increasing social disadvantage (OR = 2.56 [CI: 2.27, 2.97]). Mothers of infants residing in regional or remote areas had consistently lower risk of ASD or ID and may be linked to reduced access to services or under-ascertainment rather than a protective effect of location. Conclusions The different risk profiles observed between groups may be related to aetiological differences or ascertainment factors or both. Untangling these pathways is challenging but an urgent public health priority in view of the supposed autism epidemic.

A comparison of autism prevalence trends in Denmark and Western Australia

Prevalence statistics for autism spectrum disorders (ASD) vary widely across geographical boundaries. Some variation can be explained by diagnostic methods, case ascertainment and age at diagnosis. This study compared prevalence statistics for two distinct geographical regions, Denmark and Western Australia, both of which have had population-based registers and consistent classification systems operating over the past decade. Overall ASD prevalence rates were higher in Denmark (68.5 per 10,000 children) compared with Western Australia (51.0 per 10,000 children), while the diagnosis of childhood autism was more prevalent in Western Australia (39.3 per 10,000 children) compared with Denmark (21.8 per 10,000 children). These differences are probably caused by local phenomena affecting case ascertainment but influence from biological or geographical factors may exist.

Prenatal Alcohol Exposure and Language Delay in 2-Year-Old Children: The Importance of Dose and Timing on Risk

OBJECTIVE. The aim of this study was to investigate the association of dose and timing of prenatal alcohol exposure with early language acquisition. METHODS. We examined language delay in a randomly selected, population-based sample of Western Australian children born in 1995–1996 whose mothers had agreed to participate in a longitudinal study on health-related behaviors and who had completed the 2-year questionnaire (N = 1739). Information on alcohol consumption was collected at 3 months after birth for four periods; the three months pre-pregnancy and for each trimester separately. Prenatal alcohol exposure was grouped into none, low, moderate-heavy and binge (>5) based on the total quantity consumed per week, quantity consumed per occasion, and frequency of consumption. The communication scale from the Ages & Stages Questionnaire was used to evaluate language delay. Logistic regression analysis was used to generate odds ratios and 95% confidence intervals, adjusted for confounding factors. RESULTS. There was no association between low levels of alcohol consumption and language delay at any time period, although there was a nonsignificant 30% increase in risk when moderate-to-heavy levels of alcohol were consumed in the third trimester. Children exposed to a binge pattern of maternal alcohol consumption in the second trimester had nonsignificant, three-fold increased odds of language delay, with a similar estimate following third trimester alcohol exposure after controlling for covariates. CONCLUSIONS. This study did not detect an association between low levels of prenatal alcohol exposure and language delay when compared with women who abstained from alcohol during pregnancy. A nonsignificant threefold increase in the likelihood of language delay was seen in children whose mothers binged during late pregnancy. However, the small numbers of women with a binge-drinking pattern in late pregnancy limited the power of this study; studies analyzing larger numbers of children exposed to binge drinking in late pregnancy are needed.

Birth Defects in Children With Autism Spectrum Disorders: A Population-based, Nested Case-Control Study

The causes of autism spectrum disorders (ASDs) are unknown, although genetic and environmental influences have been implicated. Previous studies have suggested an association with birth defects, but most investigators have not addressed associations with specific diagnostic categories of ASD. In this study, the authors investigated the associations between birth defects and autism, Asperger syndrome, and pervasive developmental disorder not otherwise specified. Using Western Australian population-based linked data, the authors compared all children with ASD born in Western Australia during 1980-1995 (n = 465) with their siblings (n = 481) and population controls (n = 1,313) in a nested case-control study. The prevalence of birth defects was significantly higher in ASD cases than in population controls; this difference remained significant after adjustment for confounding factors. Odds ratios for birth defects were similar for autism (odds ratio (OR) = 2.0, 95% confidence interval (CI): 1.3, 3.0) and pervasive developmental disorder not otherwise specified (OR = 2.2, 95% CI: 1.1, 4.3) but not for Asperger syndrome (OR = 0.5, 95% CI: 0.1, 1.9). Birth defects in case siblings were not significantly different from those in cases and population controls. The association between birth defects and ASD may be due to underlying genetic and/or environmental factors common to both ASD and birth defects, or birth defects may predispose a child to ASD.

Developmental outcomes of newborn encephalopathy in the term infant

Newborn ecephalopathy is a clinically defined condition of abnormal neurological behaviours in the newborn period. Though most cases have their origin in the preconceptional and antepartum period, newborn encephalopathy represents a crucial link between intrapartum events and permanent neurological problems in the child. The birth prevalence of newborn encephalopathy ranges from 1.8 to 7.7 per 1000 term live births according to the definition used and the population to which it is applied. Few studies have investigated the outcomes of newborn encephalopathy other than for cases solely attributed to intrapartum hypoxia. These adverse outcomes range from death to cerebral palsy, intellectual disability, and less severe neurological disabilities such as learning and behavioural problems. Outcomes following newborn encephalopathy may vary from country to country with 9.1% of affected babies dying in the newborn period in Western Australia and 10.1% manifesting cerebral palsy by the age of two. These compare to a case fatality of 30.5% in Kathmandu and a cerebral palsy rate of 14.5% by one year of age. The study by Robertsonet al which followed children with hypoxic ischaemic encephalopathy found an incidence of impairment of 16% among survivors assessed at 8 years with 42% requiring school resource room help or special classes. This review emphasises the great need for comprehensive clinical and educational assessment as these infants approach school entry to enable appropriate educational provisions to be made.

Cranial ultrasound as a predictor of outcome in term newborn encephalopathy

As part of a patient-based case-control study of newborn encephalopathy, we examine the cranial ultrasound results of 212 patients to determine the validity of ultrasound in predicting an adverse outcome. Forty-six (22%) patients died or developed cerebral palsy (adverse outcome) by 2 years of age. On the basis of clinical decision, 125 (60%) patients had an ultrasound before 72 hours of age; of these, 29% had an adverse outcome. The resistive index is the primary measure of interest, with a value of 0.55 or less considered abnormal. Infants with an abnormal resistive index are 8.8 times (P < 0.001) more likely to have an adverse outcome than those with a normal result. The positive predictive value of an abnormal resistive index was 71%. The results are similar for the subgroup with intrapartum hypoxia and the subgroup that had ultrasound performed before 24 hours of age. It is clear that resistive index results cannot be used in isolation, although they may have a place, in combination with other factors, in the counseling of parents and, cautiously, in the clinical management of patients.

Maternal awareness of fetal seizures in pregnancies resulting in newborn encephalopathy

From the TVW Telethon Institute for Child Health Research, Western Australia, the Department of Obstetrics and Gynaecology, Hornsby Hospital, University of Sydney, New South Wales, the Department of Neonatology, The New Children’s Hospital, Royal Alexandra Hospital for Children, Department of Paediatrics, University of Sydney, New South Wales, the Department of Neonatology, Princess Margaret Hospital for Children, Western Australia, and the Department of Paediatrics, University of Western Australia, Australia

Can parents accurately screen children at risk of developmental delay

Aim:  To evaluate the validity and potential value of the parent‐completed Infant/Child Monitoring Questionnaire (IMQ) as a screening measure for developmental delay in high‐risk infants.