Susan Sayers

An Australian Aboriginal birth cohort: a unique resource for a life course study of an Indigenous population. A study protocol

BackgroundThe global rise of Type 2 diabetes and its complications has drawn attention to the burden of non-communicable diseases on populations undergoing epidemiological transition. The life course approach of a birth cohort has the potential to increase our understanding of the development of these chronic diseases. In 1987 we sought to establish an Australian Indigenous birth cohort to be used as a resource for descriptive and analytical studies with particular attention on non-communicable diseases. The focus of this report is the methodology of recruiting and following-up an Aboriginal birth cohort of mobile subjects belonging to diverse cultural and language groups living in a large sparsely populated area in the Top End of the Northern Territory of Australia.MethodsA prospective longitudinal study of Aboriginal singletons born at the Royal Darwin Hospital 1987–1990, with second wave cross-sectional follow-up examination of subjects 1998–2001 in over 70 different locations. A multiphase protocol was used to locate and collect data on 686 subjects with different approaches for urban and rural children. Manual chart audits, faxes to remote communities, death registries and a full time subject locator with past experience of Aboriginal communities were all used.DiscussionThe successful recruitment of 686 Indigenous subjects followed up 14 years later with vital status determined for 95% of subjects and examination of 86% shows an Indigenous birth cohort can be established in an environment with geographic, cultural and climatic challenges. The high rates of recruitment and follow up indicate there were effective strategies of follow-up in a supportive population.

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.

Large waist but low body mass index: the metabolic syndrome in Australian Aboriginal children.

OBJECTIVE To describe the prevalence and clinical characteristics of the metabolic syndrome (MetS) in a cohort of Australian Aboriginal children. STUDY DESIGN Body mass index (BMI), waist circumference, skin fold thickness, body fat percentage, insulin resistance, and the prevalence of MetS were evaluated in 486 children age 9 to 14 years from the Darwin Health Region, Northern Territory, Australia. RESULTS Using an age- and sex- specific definition, 14% of the children in the cohort had MetS, 6.4% were overweight, 4.9% were obese, and 26.2% had an elevated waist circumference. The mean percentage of body fat was 30.2%. The children with MetS had higher BMI and waist z-scores, percent body fat, Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) score, and skin fold thickness compared with those without MetS (P < .001); however, >50% of those with MetS were neither overweight nor obese. Waist circumference was significantly associated with insulin resistance as measured by the HOMA-IR (P < .001). CONCLUSIONS MetS is common in our cohort despite low rates of overweight and obesity. A tendency for central adiposity is already evident in these young children. Measurement of waist circumference may help identify Aboriginal children at high risk for MetS.

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

BackgroundOral 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.MethodsData 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).ResultsThe 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).ConclusionsSevere 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.

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

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.

Apo-B/AI ratio identifies cardiovascular risk in childhood: the Australian Aboriginal Birth Cohort study.

We describe the lipoprotein and apolipoprotein profiles and their relationship to cardiovascular risk factors in Australian Aboriginal children. This cross-sectional study within a longitudinal birth cohort study involved Australian Aboriginal children born between 1987 and 1990 and re-examined between 1998 and 2001. Height, weight, blood pressure, waist circumference, body fat percentage, cholesterol, triglycerides, HDL-c, LDL-c, apolipoprotein B and A1 were measured. Mean age was 11.4 years (52% male). Mean cholesterol, triglyceride, HDL-c and LDL-c did not differ from reference data. Measures of obesity, blood pressure and prevalence of the metabolic syndrome did not differ in those children with lipoproteins in the upper quartile of the cohort (lower quartile for HDL-c). Boys with an Apo-B/A1 ratio in the upper quartile of the cohort had higher BMI z-score, waist z-score, % body fat, diastolic blood pressure and frequency of the metabolic syndrome (p<0.05). In girls, waist circumference, % body fat and the prevalence of the metabolic syndrome was higher in those with an Apo-B/A1 ratio in the upper quartile (p<0.05).The Apo-B/A1 ratio may be useful to identify cardiovascular risk in Australian Aboriginal children and is suited to clinical practice as the assays are standardised, accurate, automated and a fasting sample is not required.

An evaluation of three methods used to assess the gestational age of Aboriginal neonates

Abstract Many Aboriginal women do not recall their last menstrual period date, so alternative methods of estimating gestational age are necessary for optimal obstetric and neonatal care. In this retrospective review of 605 Aboriginal infants born at the Royal Darwin Hospital, the gestational age was estimated by the Dubowitz method and compared with available gestational age estimates from first fundal height and first ultrasound measurement. There was good agreement between the Dubowitz and ultrasound estimates of gestational age with best agreement occurring when ultrasound was done in the first trimester and worst agreement in the third trimester. Agreement between fundal height and Dubowitz estimates was poor but the measurement of fundal height was not standardized. When accurate last menstrual period information is absent, these findings suggest that good estimates of gestational age in Aboriginal neonates can be determined from the Dubowitz assessment at birth and from ultrasound measurements taken in the first trimester.

A Retrospective Longitudinal Study of Caries Development in an Australian Aboriginal Birth Cohort

There are a limited number of longitudinal investigations that examine the progression of dental disease in an indigenous population. Dental examinations of a cohort of indigenous Australians born in Darwin (Australia) between 1987 and 1990 were conducted at ages 6–8 and 11–13 years as part of the Child Dental Health Survey, and 18–20 years as part of the longstanding prospective Aboriginal Birth Cohort (ABC) study. Data was available at all ages for 145 participants. The percent DMFT >0 increased from 17.2 to 44.1 to 81.4%, representing a linear trajectory, whereas mean DMFT increased from 0.3 to 1.0 to 5.6, representing an exponential trajectory. Both trends were significant. At age 18–20 years, the percent DMFT >0 among ABC study participants was 1.2 times that of their counterparts at a national level. The differences were more marked when dental caries severity was considered, with mean DMFT among 18- to 20-year-old ABC study participants being 1.7 times that of similarly aged adults at a national level. Most of this disparity was constituted by the decayed component, with ABC study participants having eight times the mean DT of their national-level counterparts. The findings indicate that Aboriginal young adults in this birth cohort experience a disproportionate amount of dental disease relative to their non-indigenous counterparts, and that this pattern is consistent across the life course.

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

BackgroundSocial 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 Australias Northern Territory.MethodsData 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.ResultsAfter 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.ConclusionThe 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.