Belinda Davison

Australian Aboriginal Birth Cohort study: follow-up processes at 20 years

BackgroundIn 1987, a prospective study of an Australian Aboriginal Birth Cohort was established focusing on the relationships of fetal and childhood growth with the risk of chronic adult disease. However as the study is being conducted in a highly marginalized population it is also an important resource for cross-sectional descriptive and analytical studies. The aim of this paper is to describe the processes of the third follow up which was conducted 20 years after recruitment at birth.MethodsProgressive steps in a multiphase protocol were used for tracing, with modifications for the expected rural or urban location of the participants.ResultsOf the original 686 cohort participants recruited 68 were untraced and 27 were known to have died. Of the 591 available for examination 122 were not examined; 11 of these were refusals and the remainder were not seen for logistical reasons relating to inclement weather, mobility of participants and single participants living in very remote locations.ConclusionThe high retention rate of this follow-up 20 years after birth recruitment is a testament to the development of successful multiphase protocols aimed at overcoming the challenges of tracing a cohort over a widespread remote area and also to the perseverance of the study personnel. We also interpret the high retention rate as a reflection of the good will of the wider Aboriginal community towards this study and that researchers interactions with the community were positive. The continued follow-up of this life course study now seems feasible and there are plans to trace and reexamine the cohort at age 25 years.

Improving sexual health for young people: making sexuality education a priority

How well do young people understand their developing sexuality and what this means? This paper reports on findings from the Our Lives: Culture, Context and Risk project, which investigated sexual behaviour and decision-making in the context of the everyday life experience and aspirations of Indigenous and non-Indigenous young people (16–25 years) in the Northern Territory, Western Australia and in South Australia. Using qualitative data, this paper focuses on what participating young people thought was necessary to improve the quality of sexuality education. Participants suggest that current forms of sexuality education are too clinical, didactic and unengaging, and are missing in relevant content. Young people requested more information on relationships, first sexual experiences and negotiating condom use. These requests indicate that young people realise that they need more knowledge in order to have healthy relationships, which conflicts with the popular belief that providing young people with open, honest information around sex will encourage them to have sex or increase sexual risk taking. Making sexuality education more of a priority and listening to the needs of young people could be a positive step towards improving sexual health and well-being.

Childhood metabolic syndrome, inflammation and carotid intima-media thickness. The Aboriginal Birth Cohort Study☆

BACKGROUND/OBJECTIVES We evaluated whether atherosclerotic changes associated with MetS in Australian Aboriginals are reversible in childhood. In addition, we investigated whether heightened inflammation is mediating the adverse effects of MetS. METHODS The study cohort comprised of 351 children from the Aboriginal Birth Cohort Study (a longitudinal study based in the Northern Territory of Australia) aged 9-13 years at baseline examination who were followed up 6 years later. MetS was defined by at least three of the following parameters within the extreme sex- and age-specific quartile: highest quartile for waist circumference, blood pressure, triglycerides, and glucose, and lowest quartile for HDL-cholesterol. Carotid intima-media thickness (IMT) and C-reactive protein (CRP) were assessed at follow-up. RESULTS Individuals with MetS at baseline or follow-up had increased carotid IMT at follow-up (mean ± SEM 539 ± 3 vs. 561 ± 8 μm, P=0.007; and 537 ± 3 vs. 567 ± 8 μm, P<0.0001 respectively). In combined analyses from baseline and follow-up studies, those individuals with MetS only at baseline had partially improved vascular status; their IMT was not significantly increased compared to those without MetS at both time-points (534 ± 3 vs. 550 ± 10 μm, P=0.09). At the follow-up examination, MetS status was associated with increased IMT levels only among individuals with CRP levels above the median (≥ 2.1mg/l) (536 ± 5 vs. 573 ± 9 μm, P<0.0001, P for interaction 0.01). CONCLUSIONS MetS in childhood is associated with subclinical atherosclerosis in an Australian Aboriginal population and the effects appear to be mediated by increased inflammation. The extent of atherosclerosis was partially reduced if metabolic status improved during the follow-up.

Engaging adolescents and young adults in a longitudinal health study: experience from the Top End cohort.

AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH 2011 vol. 35 no. 1

Indigenous Australian household structure: a simple data collection tool and implications for close contact transmission of communicable diseases

Households are an important location for the transmission of communicable diseases. Social contact between household members is typically more frequent, of greater intensity, and is more likely to involve people of different age groups than contact occurring in the general community. Understanding household structure in different populations is therefore fundamental to explaining patterns of disease transmission in these populations. Indigenous populations in Australia tend to live in larger households than non-Indigenous populations, but limited data are available on the structure of these households, and how they differ between remote and urban communities. We have developed a novel approach to the collection of household structure data, suitable for use in a variety of contexts, which provides a detailed view of age, gender, and room occupancy patterns in remote and urban Australian Indigenous households. Here we report analysis of data collected using this tool, which quantifies the extent of crowding in Indigenous households, particularly in remote areas. We use these data to generate matrices of age-specific contact rates, as used by mathematical models of infectious disease transmission. To demonstrate the impact of household structure, we use a mathematical model to simulate an influenza-like illness in different populations. Our simulations suggest that outbreaks in remote populations are likely to spread more rapidly and to a greater extent than outbreaks in non-Indigenous populations.

Sub-optimal protection against past hepatitis B virus infection where subtype mismatch exists between vaccine and circulating viral genotype in northern Australia.

BACKGROUND In Australias Northern Territory, the hepatitis B virus (HBV) subgenotype A2 (subtype adw2) vaccine was introduced in 1988 for Indigenous infants. Subsequently, the circulating viral genotype has been identified as subgenotype C4 (subtype ayw3). We assessed HBV vaccine effectiveness (VE) in light of this subtype mismatch. METHODS Participants of the Aboriginal Birth Cohort (ABC) study were recruited at birth (1987-1990), with HBV serology obtained at follow-up waves 3 (2005-2007) and 4 (2013-2015). Participants were immune if HBV surface antibody levels exceeded 10 IU/L. We determined the VE against any HBV infection (anti-HBc+) and against chronic infection (HBsAg+ or HBV DNA+), comparing non-vaccinated participants with those fulfilling United States Centers for Disease Control and Prevention (CDC) criteria for full HBV immunisation. RESULTS Of 686 participants in the ABC study, we obtained HBV serology from 388 at wave 4. 181 participants were immune to HBV and 97 had evidence of any infection. Seven participants were chronically infected, of whom five had received three vaccine doses, and anti-HBc seroconversion had occurred subsequent to the three vaccine doses for two of these seven participants. Comparing the 107 participants who had been vaccinated in accordance with CDC recommendations and 127 who had not been vaccinated, VE against any infection was 67% (95%CI, 43-104%). The odds of being anti-HBc+ was 87% lower in participants raised in urban settings compared to those born into families from remote areas (OR, 0.1; 95%CI, 0.03-0.4). CONCLUSIONS In a setting where there exists a subtype mismatch between vaccine and circulating genotype, the vaccine was largely effective in preventing chronic infection but sub-optimal against any infection. The implications of a high prevalence of anti-HBc seropositivity in this population are unclear and require further study. The fact that anti-HBc seropositivity was strongly associated with remote dwelling suggests ongoing viral exposure in remote settings.

Association of anthropometric measures and cardiovascular risk factors in children and adolescents: findings from the Aboriginal Birth Cohort study

This study examined the association of anthropometric measures including height, leg length, trunk length and body mass index (BMI) at 11 and 18 years with systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol, low-density lipoprotein cholesterol (LDL-c) and high-density lipoprotein cholesterol (HDL-c) at 11 and 18 years. We analysed data from 661 participants from the Aboriginal Birth Cohort study–a longitudinal study based in the Northern Territory, Australia. Associations between anthropometric measures and cardiovascular risk factors were investigated in linear regression analyses adjusted for confounding, with imputation for missing data. In adjusted analyses, increasing leg length [males: 0.47mmHg/cm (0.23, 0.72); females: 0.50mmHg/cm (0.18, 0.83)], trunk length [males: 0.50mmHg/cm (0.28, 0.73); females: 0.57mmHg/cm (0.33, 0.81)] and height [males: 0.32mmHg/cm (0.16, 0.48); females: 0.32mmHg/cm (0.12, 0.52)] at 11 years was associated with higher SBP at 11 years. When these exposures were measured at 18 years the effect on SBP at 18 years had attenuated, and only increased trunk length was associated with higher SBP at 18 years for both sexes [males: 0.46mmHg/cm (0.05, 0.87); females: 0.69mmHg/cm (0.30, 1.08)]. We observed little association between height, leg length and trunk length and DBP, total cholesterol, LDL-c and HDL-c. Increased BMI was associated with elevated SBP and DBP at 11 and 18 years. Our findings suggest that height, leg length, and trunk length measured at 11 and 18 years was generally not associated with cardiovascular risk factors at 11 and 18 years. However, greater childhood BMI was associated with higher blood pressure and this association persisted into adolescence. This study contributes to the limited body of evidence on the association between measures of early anthropometry and cardiovascular risk among the Australian Aboriginal population.

Early life determinants of cardiovascular health in adulthood. The Australian Aboriginal Birth Cohort study

Abstract Background In 2010, The American Heart Association (AHA) set seven impact goals for ideal cardiovascular health (CVH): ideal blood pressure (BP), glucose, cholesterol levels and body mass index (BMI), physical activity on recommended levels, non-smoking and a healthy diet. We explored the prevalence of ideal CVH and the relationship between early life determinants and later CVH in an Aboriginal Birth Cohort in Australia. Methods The sample comprised 686 Aboriginal babies born in Darwin between 1987 and 1990. At birth, birthweight was measured and data was gathered about the families. A follow-up was conducted in adulthood. Prevalences of CVH metrics were assessed and each participant received an AHA score between 0 and 7. The relationship between socioeconomic factors at birth and later CVH was analysed. Results Ideal CVH was rare. Females had higher levels of ideal blood pressure (OR 5.87, P  Conclusions Several early life factors affect later CVH in this cohort. These factors could be of significance in reducing the gap in cardiovascular mortality and morbidity between the Aboriginal and the non-Aboriginal populations in Australia.

Life, lifestyle and location: examining the complexities of psychological distress in young adult Indigenous and non-Indigenous Australians

Mental health is fundamental to an individuals health and well-being. Mental health disorders affect a substantial portion of the Australian population, with the most vulnerable time in adolescence and young adulthood. Indigenous Australians fare worse than other Australians on almost every measure of physical and mental health. Cross-sectional data from young adults (21-27 years) participating in the Life Course Program, Northern Territory, Australia, is presented. Rates of psychological distress were high in remote and urban residing Indigenous and urban non-Indigenous young adults. This rate was more pronounced in young women, particularly in Indigenous remote and urban residing women. Young adults with high psychological distress also had lower levels of positive well-being, higher perceived stress levels, experienced a higher number of major life events and were at an increased risk of suicidal ideation and/or self-harm. This study supports the need for a continued focus on early screening and treatment at this vulnerable age. The significant association seen between psychological distress and other markers of emotional well-being, particularly risk of suicidal ideation and/or self-harm, highlights the need for a holistic approach to mental health assessment and treatment. A concerted focus on improving the environs of young adults by lowering levels of stress, improving access to adequate housing, educational and employment opportunity, will assist in improving the emotional health of young adults.