Beverly Petterson

The changing survival profile of people with Down's syndrome: implications for genetic counselling

Cohort studies have indicated that the survival of individuals with Downs syndrome has dramatically increased over the past 50 years. Early childhood survival in particular has shown major improvement, due largely to advances in cardiac surgery and in general health management. The present study was based on a continuous cohort of 1332 people with Downs syndrome in Western Australia, registered for intellectual disability services between 1953 and 2000. Their life expectancy was 58.6 years, 25% lived to 62.9 years, and the oldest living person is 73 years of age. Life expectancy for males was greater than females by 3.3 years. The substantial increase in survival across the study period means that the life expectancy of people with Downs syndrome is approaching that of the general population, but accompanied by a range of significant mid‐life health problems. The findings are of relevance to all developed countries and have considerable implications in terms of the counselling information provided to families at risk of having a child with Downs syndrome.

What constitutes cerebral palsy

Cerebral palsy (CP) is a term of convenience applied to a group of motor disorders of central origin defined by clinical description. It is not a diagnosis in that its application infers nothing about pathology, aetiology, or prognosis. It is an umbrella term covering a wide range of cerebral disorders which result in childhood motor impairment. The precise inclusion criteria vary with the objectives for using the term. For meaningful comparison of rates of CP, as performed by and between CP registers, it is important that the rates should be generated using the same criteria. As generally understood there must be motor impairment, and this impairment must stem from a malfunction of the brain (rather than spinal cord or muscles). Furthermore, the brain malfunction must be non‐progressive and it must be manifest early in life. For the purposes of comparisons of rates across time even when the condition meets all the above criteria, it must not historically have been excluded from the category of CP. This paper addresses the problem of standardizing the inclusion criteria for selecting people included on CP registers with particular reference to this last criterion.

On the twin risk in autism.

Autism is considered by many to be the most strongly genetically influenced multifactorial childhood psychiatric disorder. In the absence of any known gene or genes, the main support for this is derived from family and twin studies. Two recent studies (Greenberg et al. 2001; Betancur et al. 2002) suggested that the twinning process itself is an important risk factor in the development of autism. If true, this would have major consequences for the interpretation of twin studies. Both studies compared the number of affected twin pairs among affected sib pairs to expected values in two separate samples of multiplex families and reported a substantial and significant excess of twin pairs. Using data from our epidemiological study in Western Australia, we investigated the possibility of an increased rate of autism in twins. All children born between 1980 and 1995 with autism, Asperger syndrome, or pervasive developmental disorder not otherwise specified (PDD-NOS) were ascertained. Of the 465 children with a diagnosis, 14 were twin births (rate 30.0/1,000) compared to 9,640 children of multiple births out of a total of 386,637 births in Western Australia between 1980 and 1995 (twin rate weighted to number of children with autism or PDD per year 26.3/1,000). These data clearly do not support twinning as a substantial risk factor in the etiology of autism. We demonstrate that the high proportion of twins found in affected-sib-pair studies can be adequately explained by the high ratio of concordance rates in monozygotic (MZ) twins versus siblings and the distribution of family size in the population studied. Our results are in agreement with those of two similar studies by Croen et al. (2002) in California and Hultman et al. (2002) in Sweden.

Twins born following assisted reproductive technology: perinatal outcome and admission to hospital

BACKGROUND Compared with spontaneously conceived (SC) singletons, adverse perinatal outcome, neonatal intensive care unit (NICU) admission and hospital admission in infancy are more common in those born following Assisted Reproductive Technology (ART). Similar comparisons for twins have shown conflicting results. METHODS We investigated perinatal outcome and hospital admission during the first 3 years of life for all twin children born in Western Australia between 1994 and 2000 [700 ART, 4097 SC]. RESULTS ART twins had a greater risk of adverse perinatal outcome including preterm birth, low birthweight and death compared with SC twins of unlike-sex. In their first year of life, ART twins had a longer birth admission; were 60% more likely to be admitted to a NICU; and had a higher risk of hospital admission. The increased risk of hospital admission continued in the second and third year but was not statistically significant in the third year. CONCLUSIONS Couples undertaking ART should be aware that in addition to the known increased perinatal risks associated with a twin birth, ART twins are more likely than SC twins to be admitted to a NICU and hospitalized in the first 3 years of life.

Breast cancer and the uptake of mammography screening services by women with intellectual disabilities

BACKGROUND It is estimated that approximately 50% of women in Australia with intellectual disability will live to 70 years of age and as a result many will fall within the age group at highest risk for breast cancer (50-69 years). METHODS Subjects were identified through the Western Australia Disability Services database. To determine the number of women diagnosed with breast cancer during the period 1982-2000, individual records (n = 2,370) were linked to the Western Australia Cancer Registry and the Mammography Screening Registry. RESULTS The incidence of breast cancer among women with intellectual disability was 64.0 per 100,000 person-years, by comparison with 146.7 per 100,000 person-years in the general population. The uptake of breast cancer screening was examined in a subgroup of 380 women, 34.7% of whom had used mammographic screening, as opposed to 54.6% screening uptake in the general population. Failure to use screening services was highest in women who were unmarried, and was positively associated with severity of intellectual disability, presence of physical disabilities, and urban residence. CONCLUSIONS The lower incidence of breast cancer in women with intellectual disability may in part be attributable to decreased life expectancy, but it also appears to reflect significant under utilization of the readily available screening services.

IDEA (Intellectual Disability Exploring Answers): A population-based database for intellectual disability in Western Australia

Despite the demands it places on individuals, families and the community, intellectual disability (ID) is a neglected area of public health. Accurate estimates of prevalence are sparse and range from 0.5 to 3.0%. The cause of the condition is unknown in at least 50% of cases. This paper describes the Intellectual Disability Exploring Answers (IDEA) database set up in Western Australia to provide an infrastructure for research and to facilitate the planning of service provision for people with ID. Since 1953 a database for ID has been maintained in Western Australia, a state with a population of 1.95 million in an area of 2.52 million km2. The current IDEA database aims to obtain ongoing population-based ascertainment of ID from providers of clinical and educational services, with the potential for linkage to a network of other state databases. The average prevalence of ID for children born in Western Australia over the years 1983–1996 was 15.2 per 1000 live births, with 50% ascertained only through the education system. During this time period 60% of cases were male. Of children with an ID born in Western Australia in 1980–1999 and surviving to 1 year, 30.1% had a birth defect, and the prevalence ratio of birth defects in this group compared to the population with no birth defects was 6.5 (CI 6.3–6.8).

Autism following a history of newborn encephalopathy: More than a coincidence?

Between June 1993 and December 1996, 276 term newborn infants with encephalopathy and 564 randomly selected term controls were enrolled in a population‐based study of moderate and severe term newborn encephalopathy (NE) in Western Australia. During comprehensive neurobehavioural and cognitive follow‐up of all patients and controls at 3 years and again at 5 years of age we found an unexpected but strong association between NE and autism spectrum disorders (ASDs). A diagnosis of ASD by age 5 years was reached using criteria according of the Diagnostic Statistical Manual, 4th edition. Linking records to the Western Australian Disability Services Commission Register ensured that no child in the study with ASD was missed. By age 5 years, 37 (13.4%) infants with NE and one (0.2%) control had died. Among the 239 survivors of NE, 12 (5%) were diagnosed with an ASD. Of these, 10 (4.2%) met the full criteria for autism, one had pervasive developmental disorder‐not otherwise specified, and one had Asperger syndrome. Among the 563 surviving controls, five (0.8%) were diagnosed with an ASD: three with autism, one with autism/possible Asperger syndrome, and one with Asperger syndrome. Compared with the controls, the children who had experienced NE were 5.9 times (95% confidence interval 2.0–16.9) more likely to have been diagnosed with an ASD.

SPASTIC QUADRIPLEGIA IN WESTERN AUSTRALIA: A GENETIC EPIDEMIOLOGICAL STUDY. I: CASE POPULATION AND PERINATAL RISK FACTORS

In a case‐control study of all cerebral palsy cases with moderates and serve spastic quadriplegia born between 1976 and 1985, males comprised three‐quarters of the cases and tended to have more sevre motor impairment than females. The majority of cases had multiple and serve disabilities, and 27 per cent had died by the time of data collection. There was an excess of low‐birthweight and preterm births compared with all live births in WA. An intrapartum casuse was considered possible in 18 of the 74 children; however, half of these had evidence of compromise before labour.

Adverse outcome after multiple pregnancy

There is increasing interest in the outcomes of multiple pregnancies as their numbers rise, mainly owing to advances in fertility-enhancing techniques. In addition, the numbers of multiple births surviving the perinatal period is increasing with the increasing survival of very tiny babies. In order to investigate these outcomes or to evaluate procedures that may improve them, it is important to consider a number of methodological issues that affect the comparability of data both between and within populations. How a birth and a multiple birth are defined, data sources, whether multiple pregnancies or individual births are being counted and the identification of multiple gestations by zygosity and chorionicity will all affect the reported outcome rates. In light of this, perinatal mortality and neurodevelopmental disabilities are examined as adverse outcomes of multiple pregnancies.

Intellectual disability in Western Australia

Objective: To investigate the prevalence of intellectual disability in Western Australia (WA), its causes, prevention, and trends over time.