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.

Pathways between birth weight and later body size in predicting blood pressure: Australian Aboriginal Cohort Study 1987-2007.

BACKGROUND: Although a large number of previous studies suggest an association between birth weight and later blood pressure, others do not. Controversy surrounds the relative importance of these associations, in particular in relation to more modifiable factors in later life and whether the association would be seen in a, relatively disadvantaged, Indigenous population. The aim of this study, within the Aboriginal Birth Cohort study, was to examine the relative contributions and mediating pathways of birth weight, and later growth and lifestyle factors to variation in blood pressure at age 16-20 years. METHODS: Detailed information was collected prospectively, including maternal smoking, birth weight, childhood BMI. At age 16-20 years, 451 underwent clinical examination, including the measurement of diastolic and systolic blood pressures. These data were analyzed using linear regression and path analyses, incorporating adjustment for potential confounders. RESULTS: Increased BMI at age 18 years was significantly associated with both increasing systolic and diastolic blood pressures. BMI had the highest relative importance and mediated the effects from earlier in life, including birth weight. Being female and living in remote residence were also independently associated with a reduction in systolic blood pressure. CONCLUSION: Blood pressure in this cohort is primarily influenced by contemporaneous BMI, which in this population at this age is generally lower than that seen in non-Indigenous populations in developed countries. However, other factors, including birth weight, do appear to play a role that is mediated through later BMI.

Prevalence and validity of self-reported smoking in Indigenous and non-Indigenous young adults in the Australian Northern Territory.

BACKGROUND: In this study, we used data from Australia's Northern Territory to assess differences in self-reported smoking prevalence between the Indigenous and non-Indigenous populations. We also used urinary cotinine data to assess the validity of using self-reported smoking data in these populations. METHODS: The Aboriginal Birth Cohort (ABC) is a prospective study of 686 Aboriginal babies born in Darwin 1987-90. The Top End Cohort (TEC) is a study of non-Indigenous adolescents, all born in Darwin 1987-91. In both studies, participants aged between 16 and 21 years, were asked whether they smoked. Urinary cotinine measurements were made from samples taken at the same visits. RESULTS: Self-reported smoking prevalence was 68% in the ABC and 14% in the TEC. Among the self-reported non-smokers, the median cotinine levels were higher in the ABC (33 ng/ml) than in the TEC (5 ng/ml), with greater percentages of reported non-smokers in the under 50 ng/ml group in the TEC than in the ABC CONCLUSIONS: Prevalence of smoking was much higher in the ABC than in the TEC. The higher cotinine levels in ABC non-smokers may reflect an underestimated prevalence, but is also likely to reflect higher levels of passive smoking. A broader approach encompassing social, cultural and language factors with increased attention to smoking socialisation factors is required.

Challenges and strategies for cohort retention and data collection in an indigenous population: Australian Aboriginal Birth Cohort.

BACKGROUND: Longitudinal prospective birth cohort studies are pivotal to identifying fundamental causes and determinants of disease and health over the life course. There is limited information about the challenges, retention, and collection strategies in the study of Indigenous populations. The aim is to describe the follow-up rates of an Australian Aboriginal Birth Cohort study and how they were achieved. METHODS: Participants were 686 babies enrolled between January 1987 and March 1990, born to a mother recorded in the Delivery Suite Register of the Royal Darwin Hospital (RDH) as a self-identified Aboriginal. The majority of the participants (70%) resided in Northern Territory within rural, remote and very remote Aboriginal communities that maintain traditional connections to their land and culture. The Aboriginal communities are within a sparsely populated (0.2 people/ km2) area of approximately 900,000 km² (347 sq miles), with poor communication and transport infrastructures. Follow-ups collecting biomedical and lifestyle data directly from participants in over 40 locations were conducted at 11.4 years (Wave-2) and 18.2 years (Wave-3), with Wave-4 follow-up currently underway. RESULTS: Follow-ups at 11 and 18 years of age successfully examined 86% and 72% of living participants respectively. Strategies addressing logistic, cultural and ethical challenges are documented. CONCLUSIONS: Satisfactory follow-up rates of a prospective longitudinal Indigenous birth cohort with traditional characteristics are possible while maintaining scientific rigor in a challenging setting. Approaches included flexibility, respect, and transparent communication along with the adoption of culturally sensitive behaviours. This work should inform and assist researchers undertaking or planning similar studies in Indigenous and developing populations.

Birthweight and fasting glucose and insulin levels: results from the Aboriginal Birth Cohort Study.

OBJECTIVE: To examine the relationships between birthweight, current size, and fasting glucose and fasting insulin levels in Aboriginal adolescents. DESIGN, PARTICIPANTS AND SETTING: Longitudinal prospective study of a Northern Territory Aboriginal birth cohort of 686 Aboriginal babies born at the Royal Darwin Hospital between January 1987 and March 1990, and followed up between December 2006 and January 2008 in over 40 NT locations. MAIN OUTCOME MEASURES: Fasting insulin and glucose levels, adjusted for gestational age, sex and contemporary age. RESULTS: Among the 134 participants with complete data, those with fetal growth restriction (FGR) or low birthweight (LBW) at birth were not overweight at 18 2013s. In these circumstances, birthweight showed a significant positively directed association with fasting glucose levels (P = 0.002). Current weight showed a significant and positively directed association with both fasting insulin (P < 0.001) and fasting glucose levels (P = 0.001), and current height showed a significant and positively directed association with insulin levels (P = 0.006). CONCLUSIONS: Birthweight was only positively associated with fasting glucose levels, with no association with fasting insulin levels. The high-risk combination for type 2 diabetes of LBW or FGR with later overweight or obesity was rare in this adolescent Aboriginal population.

Oral health and social and emotional well-being in a birth cohort of Aboriginal Australian young adults.

BACKGROUND: Social and emotional well-being is an important component of overall health. In the Indigenous Australian context, risk indicators of poor social and emotional well-being include social determinants such as poor education, employment, income and housing as well as substance use, racial discrimination and cultural knowledge. This study sought to investigate associations between oral health-related factors and social and emotional well-being in a birth cohort of young Aboriginal adults residing in the northern region of Australia's Northern Territory. METHODS: Data were collected on five validated domains of social and emotional well-being: anxiety, resilience, depression, suicide and overall mental health. Independent variables included socio-demographics, dental health behaviour, dental disease experience, oral health-related quality of life, substance use, racial discrimination and cultural knowledge. RESULTS: After adjusting for other covariates, poor oral health-related items were associated with each of the social and emotional well-being domains. Specifically, anxiety was associated with being female, having one or more decayed teeth and racial discrimination. Resilience was associated with being male, having a job, owning a toothbrush, having one or more filled teeth and knowing a lot about Indigenous culture; while being female, having experienced dental pain in the past year, use of alcohol, use of marijuana and racial discrimination were associated with depression. Suicide was associated with being female, having experience of untreated dental decay and racial discrimination; while being female, having experience of dental disease in one or more teeth, being dissatisfied about dental appearance and racial discrimination were associated with poor mental health. CONCLUSION: The results suggest there may be value in including oral health-related initiatives when exploring the role of physical conditions on Indigenous social and emotional well-being.

Fetal growth restriction and 18-year growth and nutritional status: Aboriginal birth cohort 1987-2007.

The main objective of the work is to compare the growth and nutritional status of Australian Aboriginal term infants born with (n = 81) and without fetal growth restriction (n = 260). A prospective birth cohort study of 341 Aboriginal babies from the Top End of the Northern Territory of Australia was recruited at birth (1987-1990) and re-examined at a mean age of 18.3 years (2006-2008) for outcome measures of growth and nutrition status. Those with growth restriction at birth were 3 cm shorter (P = 0.0026) and 9 kg lighter (P = 0.0001) with head circumferences 0.95 cm smaller (P = 0.0008) than those without growth restriction. The proportions of growth restricted participants with body mass index <18.5 kg/m(2) were significantly greater (P = 0.028), and those with BMI > 25 kg/m(2) and with fat percentage >85th percentile were significantly smaller (P = 0.012 and 0.004, respectively). In this cohort, those Aboriginal babies born smaller and lighter have remained smaller and lighter at 18 years of age. However, the highest risk of later chronic noncommunicable disease has been reported in subjects who were born small and become relatively larger in later life. The continued study of this Aboriginal birth cohort will give us an opportunity to determine if and when in later life the effects of birth weight are modified by environmental nutritional factors.

Lipoprotein(a) identifies cardiovascular risk in childhood: the Australian Aboriginal Birth Cohort Study.

AIM: To describe the lipoprotein(a) (Lp(a))profile and its relationship to cardiovascular risk factors in Australian Aboriginal children. METHODS: A cross-sectional study within a longitudinal birth cohort study in the Darwin Health Region (Northern Territory, Australia). Subjects were Aboriginal children born between 1987 and 1990 who were re-examined between 1998 and 2001. Outcome measures were cholesterol, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, apoB, apoA1, apoA1/B ratio, anthropometric measures, cardiovascular disease (CVD) risk factors, maternal smoking and nutrition. RESULTS: At a mean age of 11.4 years, results showed that high concentrations of Lp(a) were significantly related to well-known lipid-based CVD risk factors for both boys and girls, and that only one anthropometric factor, height, was significant for girls. Non-genetic factors and maternal smoking were not found to be significant contributors to Lp(a) concentrations. CONCLUSIONS: Lp(a) should be considered as a more effective marker of CVD than anthropometric measures, and children from families with a history of premature CVD should be regularly screened for this factor.

Indigenous perinatal and neonatal outcomes: a time for preventive strategies.

Pregnancy outcomes for Indigenous mothers and babies have improved, but marked disparities remain between Indigenous and non-Indigenous women. Many contributors to these disparities such as smoking, alcohol use, poor nutrition, infection, teenage pregnancy and stress are preventable or modifiable particularly if addressed prior to pregnancy. It is suggested that we expand our reproductive health research, education and care to a life course approach beginning in early adolescence.

Clinical oral health outcomes in young Australian Aboriginal adults compared with national-level counterparts.

OBJECTIVE: To compare clinical oral health outcomes between a birth cohort of young Australian Aboriginal adults and age-matched, national-level counterparts. DESIGN, SETTING AND PARTICIPANTS: Comparison of outcomes between the dental component of Wave-3 of the Aboriginal Birth Cohort (ABC) study--a cross-sectional study conducted between January 2006 and December 2007, nested within a prospective longitudinal investigation in the Northern Territory's Top End--and the 2004-06 National Survey of Adult Oral Health (NSAOH), a representative survey of the Australian population. Data were analysed for 442 ABC study participants and 202 NSAOH participants aged 16-20 years. MAIN OUTCOME MEASURES: Severity and prevalence of clinical oral health outcomes. RESULTS: The mean number of decayed teeth was 8.0 times higher among ABC study participants than NSAOH participants, while the prevalence of untreated decayed teeth was 3.1 times higher. ABC study participants experienced 10.8 times the prevalence of moderate or severe periodontal disease of NSAOH participants, and 1.9, 4.1 and 4.5 times the prevalence of calculus, plaque and gingivitis, respectively. CONCLUSION: Adverse clinical oral health outcomes were 2-11 times higher in a cohort of young Australian Aboriginal adults than their age-matched, nationally representative counterparts.

Substance use and periodontal disease among Australian Aboriginal young adults.

AIM: To investigate the effects of tobacco, marijuana, alcohol and petrol sniffing on periodontal disease among Australian Aboriginal young adults. DESIGN: Cross-sectional nested within a long-standing prospective longitudinal study. Setting Aboriginal communities in Australia's Northern Territory. PARTICIPANTS: Members of the Aboriginal Birth Cohort study who were recruited from birth between January 1987 and March 1990 at the Royal Darwin Hospital, Northern Territory, Australia. Data were from wave III, when the mean age of participants was 18 years. MEASUREMENTS: Clinical dental examination and self-report questionnaire. FINDINGS: Of 425 participants with complete data, 26.6% had moderate/severe periodontal disease. There was elevated risk of periodontal disease associated with tobacco [prevalence ratio (PR) = 1.59, 95% CI = 1.06-2.40], marijuana (PR = 1.44, 95% CI = 1.05-1.97) and petrol sniffing (PR = 1.83, 95% CI = 1.08-3.11), but not alcohol (PR = 0.92, 95% CI = 0.67-1.27). Stratified analysis showed that the effect of marijuana persisted among tobacco users (PR = 1.47, 95% CI 1.03-2.11). It was not possible to isolate an independent effect of petrol sniffing because all petrol sniffers used both marijuana and tobacco, although among smokers of both substances, petrol sniffing was associated with an 11.8% increased prevalence of periodontal disease. CONCLUSIONS: This is the first time that substance use has been linked with periodontal disease in a young Australian Aboriginal adult population, and the first time that petrol sniffing has been linked with periodontal disease in any population. The role of substance use in periodontal disease among this, and other, marginalized groups warrants further investigation.

Risk indicators for severe impaired oral health among indigenous Australian young adults.

BACKGROUND: Oral health impairment comprises three conceptual domains; pain, appearance and function. This study sought to: (1) estimate the prevalence of severe oral health impairment as assessed by a summary oral health impairment measure, including aspects of dental pain, dissatisfaction with dental appearance and difficulty eating, among a birth cohort of Indigenous Australian young adults (n = 442, age range 16-20 years); (2) compare prevalence according to demographic, socio-economic, behavioural, dental service utilisation and oral health outcome risk indicators; and (3) ascertain the independent contribution of those risk indicators to severe oral health impairment in this population. METHODS: Data were from the Aboriginal Birth Cohort (ABC) study, a prospective longitudinal investigation of Aboriginal individuals born 1987-1990 at an Australian regional hospital. Data for this analysis pertained to Wave-3 of the study only. Severe oral health impairment was defined as reported experience of toothache, poor dental appearance and food avoidance in the last 12 months. Logistic regression models were used to evaluate effects of demographic, socio-economic, behavioural, dental service utilisation and clinical oral disease indicators on severe oral health impairment. Effects were quantified as odds ratios (OR). RESULTS: The percent of participants with severe oral health impairment was 16.3 (95% CI 12.9-19.7). In the multivariate model, severe oral health impairment was associated with untreated dental decay (OR 4.0, 95% CI 1.6-9.6). In addition to that clinical indicator, greater odds of severe oral health impairment were associated with being female (OR 2.0, 95% CI 1.2-3.6), being aged 19-20 years (OR 2.1, 95% CI 1.2-3.6), soft drink consumption every day or a few days a week (OR 2.6, 95% 1.2-5.6) and non-ownership of a toothbrush (OR 1.9, 95% CI 1.1-3.4). CONCLUSIONS: Severe oral health impairment was prevalent among this population. The findings suggest that public health strategies that address prevention and treatment of dental disease, self-regulation of soft drink consumption and ownership of oral self-care devices are needed if severe oral health impairment among Indigenous Australian young adults is to be reduced.

Strong Souls: development and validation of a culturally appropriate tool for assessment of social and emotional well-being in Indigenous youth.

OBJECTIVE: The aim of the present study was to develop and validate an appropriate tool to assess the social and emotional well-being (SEWB) of Indigenous adolescents participating in the longitudinal Aboriginal Birth Cohort (ABC) Study. METHOD: A range of tools was assessed as to the suitability of each for use in the ABC Study. Two existing tools and a newly developed one called 'Strong Souls' were piloted in a representative group (n = 67). Strong Souls was selected as the most appropriate for use in the ABC Study, and was completed by 361 participants. Exploratory factor analysis was used to explore construct validity. Cronbach alpha was used to assess the reliability of the latent constructs and the tool overall. RESULTS: Factor analysis produced a 25-item, four-factor model accounting for 34.5% of the variance. This model demonstrated sound construct validity and reliability. Factor structure was consistent with the epidemiological literature, identifying constructs of anxiety, resilience, depression and suicide risk. While these align with observations in mainstream populations, different relationships between distinct factors, and differences in symptomatology were found in this population. For example, two key findings were: feelings of sadness and low mood were linked with anxiety and not depression; and the expression of anger was verified as a unique symptom of depression for Indigenous people. CONCLUSIONS: Strong Souls demonstrated validity, reliability and cultural appropriateness as a tool for screening for SEWB among Indigenous young people in the Northern Territory.

Indigenous newborn care.

Infant mortality and morbidity disparities occur between non-Indigenous and Indigenous populations of Australia, Canada, New Zealand, and the United States. Neonatal mortality is due to high-risk births, which vary according to prevalence of the maternal risk factors of smoking, alcohol consumption, infection, and disorders of nutritional status, whereas postneonatal mortality is predominantly influenced by environmental factors. Aside from changing socioeconomic conditions, a continuum of maternal and child health care is likely to be the most effective measure in reducing these health disparities.

Relationships between birthweight and biomarkers of chronic disease in childhood: Aboriginal Birth Cohort Study 1987-2001.

Reports of relationships between lower birthweight and later chronic diseases are mainly from populations with low rates of low birthweight (LBW) and growth-restricted births. A prospective study of an Australian Aboriginal birth cohort with a mean birthweight of 3050 g (SD 630), 16% LBW and 28% fetal growth restriction was used to examine the relationships between birthweight and selected biomarkers of chronic adult disease. At a mean age of 11.4 years (range 8.9-14), the mean weight was 35.7 kg (SD 11.8) and the mean height was 143.8 cm (SD 10.6). Using the Centers for Disease Control and Prevention (CDC) 2000 growth references, weight and height-for-age z-scores were -0.8 (SD 1.4) and -0.5 (SD 1.07) respectively and using World Health Organisation criteria, 19% of children were classified as underweight (weight for age Z-score <2.0). The relationships between birthweight and blood pressure (n = 475), total cholesterol (n = 461), Apolipoprotein A-1 (n = 343), Apolipoprotein B (n = 390), respiratory function tests (n = 427), kidney size determined by ultrasound (n = 446), urinary albumin/creatinine ratio (n = 420) and fasting triglycerides (n = 281), insulin (n = 272) and glucose (n = 279) were examined using regression models adjusted for sex, gestational age, current age and puberty status. In this population with high rates of fetal growth restriction at birth and an excess of under-nutrition at age 11 years we found that birthweight had a negative relationship with child blood pressure only, while current child weight was positively related to blood pressure, total cholesterol, Apolipoprotein B, respiratory function tests, kidney size, and fasting triglycerides, insulin and glucose.

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

BACKGROUND: In 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. METHODS: Progressive steps in a multiphase protocol were used for tracing, with modifications for the expected rural or urban location of the participants. RESULTS: Of 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. CONCLUSION: The 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.