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Biomedical subjects

A H Bittles

Publications and source records attributed to A H Bittles.

At least 19 recordsLinked to original sources
PubMed2005

An assessment of intellectual disability among Aboriginal Australians.

BACKGROUND: The health and well-being of Indigenous people is a significant global problem, and Aboriginal Australians suffer from a considerably higher burden of disease and lower life expectancy than the non-Indigenous population. Intellectual disability (ID) can further compromise health, but there is little information that documents the prevalence of ID among indigenous populations. This study provides information on ID among the Aboriginal population of Western Australia. METHODS: The Disability Services Commission (DSC) of Western Australia has maintained a statewide database of people with ID since 1953. Data on people of Aboriginal descent were extracted from the DSC database and linked to two other state-based databases, the Hospital Morbidity Data System and the Deaths Registry, with additional linkage to the National Death Index. The linked data were used to assess the prevalence, survival patterns and causes of death in Aboriginal people with ID. RESULTS: Although comprising 3.5% of the population, Aboriginal Australians represented 7.4% of all people registered for ID services. The level of ID was assessed as borderline or mild in 40.7% of cases, moderate in 19.9%, severe or profound in 12.1%, but had not been specified in 27.2% cases. Median survival was 55.1 years for men and 64.0 years for women, with a mean age at death (n = 102) of 19.6 years. The leading causes of death were respiratory diseases, diseases of the circulatory system, and accidents. CONCLUSIONS: The study presents unique population summary data for ID in the Aboriginal community of Western Australia. To provide appropriate prevention and intervention strategies, there is an urgent need for more detailed information on the prevalence and patterns of ID.

Adolescent↗
PubMed2005

Endogamy, consanguinity and community disease profiles.

Considerable attention is paid to the role of consanguineous marriage as a causative factor in the prevalence of genetic disorders. At the same time, the potential influence of community endogamy on overall levels of homozygosity and disease profiles remains largely under-investigated. With the ongoing global epidemiological transition from infectious to non-communicable disease, the impact of genetic disorders will become increasingly important and a thorough understanding of the determinants of human population-genetic structure will be all the more necessary. In particular, the genetic components of adult-onset diseases will become more obvious and assume greater significance. Similarly, refinements of study design to incorporate intercommunity genetic variation appear to be an essential prerequisite in pharmacogenetic research if the concept of individualized treatments is to achieve reality, with equivalent subject-control comparison difficulties also predicted in forensic genetics.

Consanguinity↗
PubMed2004

Consanguinity, caste and deaf-mutism in Punjab, 1921.

The effects of religion, population sub-division and geography on the prevalence of deaf-mutism were investigated using information collected in the 1921 Census of Punjab. The total sample size was 9.36 million, and comprised data on thirteen Hindu castes, seventeen Muslim biraderis and two Sikh castes. A two-way analysis of variance comparing males in Hindu castes in which consanguineous marriage was prohibited, with males in Muslim biraderis which favoured first cousin marriage, indicated major differences with respect to the patterns of deaf-mutism within each religion. In the Muslim population 9.1% of the relative variation in the prevalence of deaf-mutism was inter-biraderi, 36.8% between geographical regions, and 48.8% an interaction between biraderi and region, whereas among Hindus 46.8% of the observed variation was inter-caste, 12.8% inter-region and 33.6% due to caste region interaction. From a wider disease perspective the results obtained with the Hindu community indicate the significant genetic differentiation associated with caste endogamy. As the overwhelming majority of Hindu marriages continue to be within-caste, it can be predicted that similar levels of inter-caste differences in disease frequency currently exist. By comparison, the lower level of inter-biraderi variation among Muslims is probably indicative of the dissolution of pre-existing caste boundaries and the resultant gene pool mixing that followed the large-scale conversion of Hindus to Islam during Muslim rule in North India from the 13th to the 19th centuries.

Catchment Area, Health↗
PubMed2004

A community profile of alpha thalassaemia in Western Australia.

OBJECTIVE: To investigate the current prevalence of alpha-thalassaemia in the population of Western Australia, which has received substantial immigration from South-East Asia during the last 30 years. METHOD: Over a 1-year period commencing July 2002, alpha-thalassaemia DNA testing was performed on 920 blood samples received from the Migrant Health Service, referring doctors or pathology laboratories in Western Australia. Molecular testing for alpha-thalassaemia was performed on extracted DNA for single and double alpha-globin gene deletions and mutations by PCR. RESULTS: An alpha-globin gene abnormality was detected in 35.4% (326/920) of samples. There were 177 cases (50.6%) with a single gene deletion alpha(+)-thalassaemia, most commonly -3.7 kb, and 102 cases (31.2%) with double alpha-gene deletions (alpha(0)-thalassaemia), including 7 cases of HbH disease. CONCLUSION: Overall, the findings amount to 1.7 new cases of alpha-thalassaemia per 10,000 population in the 12-month period and demonstrate that alpha-thalassaemia is an increasingly common disorder in the Western Australian population. This has important implications for community outreach programmes, genetic counselling and the screening of at-risk populations.

Adolescent↗
PubMed2003

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.

Activities of Daily Living↗
PubMed2003

Increased frequency of the mannose-binding lectin LX haplotype in Chinese systemic lupus erythematosus patients.

Mannose-binding lectin (MBL) is an important complement-activating protein of the human immune system. As a result of one of three structural gene mutations in exon 1 (variants B, C and D) and/or the presence of a low-efficiency promoter polymorphism, MBL deficiency may be associated with increased susceptibility to infectious diseases and to autoimmune disorders, including systemic lupus erythematosus (SLE). Using a combined approach of heteroduplex generator and polymerase chain reaction, a systematic search for mutations in exon 1 and the promoter region of the MBL gene was performed in a Chinese study population comprising 41 SLE patients and 111 healthy controls. Two alleles, a wild-type allele A and a variant allele B (a previously reported mutation of GGC to GAC at codon 54), were identified in MBL exon 1. The frequency of the B allele (0.15) was higher in the SLE patients than in the healthy controls (0.09), but the difference did not attain statistical significance (P > 0.05). However, for two polymorphisms at positions -550 and -221 in the promoter region, the frequency of the low-MBL-producing haplotype (LX) in the patients (0.2073) was significantly higher than that in the controls (0.0855) (P = 0.003, relative risk = 2.79). Our results suggest that the LX haplotype represents a strong risk factor among Chinese SLE patients. Although of lesser importance, the MBL B allele also may be a risk component in the developing process of SLE in Chinese patients.

Adolescent↗
PubMed2002

Endogamy, consanguinity and community genetics.

The population of India is composed of many thousands of subpopulations, divided by geography, language, religion and caste or biraderi (patrilineage) boundaries, with endogamous marriage the norm. The net effect has been the creation of multiple genetic isolates with individual mutation profiles, but to date the clinical consequences of this highly complex differentiation have been largely ignored. In contrast, the topic of consanguinity continues to attract attention among medical and population geneticists, clinicians and social scientists. The significant progress made in India in improving childhood nutritional status and combating infectious disease means that genetic disorders have assumed ever-increasing importance. In populations where consanguineous marriage is widely practised, recessive genetic disorders will continue to gain greater prominence in the overall spectrum of ill health. At the same time this increase will in part be negated by urbanization and the move to smaller family sizes, which predictably will result in a decline in the prevalence of consanguineous unions. Developing an understanding of these changes will require a wide-ranging and multidisciplinary investigative approach for which community genetics is ideally suited.

Consanguinity↗
PubMed2002

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

Cohort studies have indicated that the survival of individuals with Down's 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 Down's 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 Down's 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 Down's syndrome.

Cohort Studies↗
PubMed2002

The influence of intellectual disability on life expectancy.

BACKGROUND: To date, relatively few representative data have been available to health planners and advocacy groups on the life expectancy of people with intellectual disability. A study of trends in the survival profiles of people with intellectual disability was undertaken to assist in the planning of appropriate medical and support services. METHODS: Since 1953, the Disability Services Commission of Western Australia has maintained a database of persons diagnosed with intellectual disability. The database was used to calculate survival probabilities on a total of 8724 individuals, 7562 of whom were still alive at the time of sampling in December 2000. RESULTS: Kaplan-Meier survival plots showed a strong negative association between severity of intellectual disability and survival, with median life expectancies of 74.0, 67.6, and 58.6 years for people with mild, moderate, and severe levels of handicap. Significant negative associations also were observed with male gender, Indigenous Australian parentage, and individuals diagnosed with a specific genetic disorder. CONCLUSIONS: The findings indicate a major and expanding increase in the service requirements of this aging, intellectually disabled population during the past two generations.

Adult↗
PubMed2001

The forensic DNA implications of genetic differentiation between endogamous communities.

In many indigenous minority populations, and among migrants from Asian and African populations now resident in western Europe, North America and Australia, there is a strong tradition of endogamy and a preference for consanguineous unions. These marriage practices can result in F(ST) values greatly in excess of the maximum value (0.01) currently recommended for forensic DNA purposes under guidelines established by the National Research Council (NRC) of the USA. To examine the possible extent of deviation from this accepted norm, three co-resident Pakistani communities were studied using 10 autosomal dinucleotide markers and six tetranucleotide markers on the Y-chromosome. The mean population subdivision coefficient (FST) value was 0.13 for the autosomal loci, and Y-chromosome loci exhibited even stronger differentiation with unique alleles identified in all three communities. The data indicate that even when sub-populations are virtually indistinguishable in terms of anthropology, geography, ethnicity or culture, they may still exhibit major genetic differentiation. Where significant population stratification is known to exist, more detailed genetic databases should be developed for forensic DNA purposes, based on reference data from each of the appropriate sub-populations and not on random or combined samples.

Consanguinity↗
PubMed2001

Imperfect units of an extended microsatellite structure involving single nucleotide changes.

Short tandem repeats (STRs) and single nucleotide polymorphisms (SNPs) are widely used as markers in human genome studies. We have characterized a highly polymorphic STR locus (D20S85) with (AAAG)n repeats, by a combination of direct DNA sequencing and single-strand conformation polymorphism (SSCP) analysis. Eight STR alleles were first identified on denaturing gels, and SSCP gels were then used to demonstrate the existence of previously indistinguishable multiple alleles at the locus on the basis of variable allelic flanking sequences. This was confirmed by direct sequencing of the alleles. Four transitions, two G to A and two A to G in the 5'-flanking region of the locus at positions 14, 22, 24, and 26 effectively subdivided the STR alleles into two groups, with frequencies of 0.431 and 0.569, respectively. The mutational processes that generated the polymorphisms involved both simple changes in the number of AAAG repeats and single nucleotide mutations in the region flanking the repeat. The findings have potential application in the avoidance of false linkage and association. A composite locus of this nature, with separate STR and SNP evolutionary histories and resulting from different mutational processes, also could have wide application in studies of selection, drift, migration and inbreeding.

Adult↗