Small for gestational age and anthropometric body composition from early childhood to adulthood: the Aboriginal Birth Cohort study.

Background: In Australia the estimated rate of small for gestational age (SGA) births is 9% among non-Indigenous births compared to 14% among Aboriginal and Torres Strait Islanders. There is limited research investigating the effect of being born SGA on body composition later in life in Indigenous Australians. Methods: Using data from the Aboriginal Birth Cohort longitudinal study, we compared the body composition of those born SGA to non-SGA by analysing anthropometric measures (height, weight, waist circumference, fat percentage [FAT%], body mass index [BMI], waist-to-height ratio, and A body shape index [ABSI]) collected at four follow-up periods (from childhood to adult). For cross-sectional analyses, linear regression models were employed to assess factors associated with anthropometric measures. For longitudinal analyses linear mixed models were employed to assess differences in anthropometric measures among SGA versus non-SGA individuals while adjusting for repeated measures. Results: The analytic baseline cohort were those who participated in Wave 2 (n = 570). In cross-sectional analyses, across all waves those born SGA had smaller anthropometric z-scores compared to non-SGA individuals (ß ranging from -0.50 to -0.25). Participants residing in urban environments were significantly larger in Waves 2 to 4 (ß ranged 0.26 to 0.65). Those born SGA had higher ABSI scores in Waves 2 and 4 (ß 0.26 and 0.37, respectively). In longitudinal analyses, those born SGA had smaller measures of body composition across the life course; these differences were larger in urban communities. In remote communities those born SGA had significantly higher ABSI scores during adolescence and young adulthood, and this difference was not observed in urban communities. Conclusion: Indigenous Australians born SGA are smaller anthropometrically later in life compared to their non-SGA counterparts. In remote communities, those born SGA had higher levels of central adiposity compared to non-SGA.

Birth weight for gestational age and later cardiovascular health: a comparison between longitudinal Finnish and indigenous Australian cohorts.

INTRODUCTION: Small or large birth weight for gestational age has been linked with later cardiovascular disease risk. However, cardiovascular risk markers from childhood to adulthood according to birth weight in diverse longitudinal settings globally have not been extensively studied. OBJECTIVES: To examine the relationship between birth weight and cardiovascular risk profile from childhood until young adulthood in two geographically and socioeconomically distinct cohorts. METHODS: Data were derived from two longitudinal birth cohort studies; one from southern Finland (Special Turku Coronary Risk Factor Intervention Project, STRIP) and one from northern Australia comprising Indigenous Australians (Aboriginal Birth Cohort, ABC). The sample included 747 Finnish participants and 541 Indigenous Australians with data on birth weight, gestational age and cardiovascular risk factors (body mass index [BMI]), waist-to-height ratio [WHtR], lipid profile, blood pressure) collected at ages 11, 18 and 25 or 26 years. Carotid intima-media thickness (cIMT) was assessed at age 18 or 19 years. Participants were categorised according to birth weight for gestational age (small [SGA], appropriate [AGA] or large [LGA]). Associations between birth weight category and cardiovascular risk markers were studied using a repeated measures ANOVA. RESULTS: Higher birth weight category was associated with higher BMI later in life in both cohorts (p=.003 for STRIP and p<.0001 for ABC). In the ABC, higher birth weight category was also associated with higher WHtR (p=.004). In the ABC, SGA participants had lower systolic and diastolic blood pressure than AGA participants (p=.028 for systolic, p=.027 for diastolic) and lower systolic blood pressure than LGA participants (p=.046) at age 25. In the STRIP cohort, SGA participants had lower cIMT than LGA participants (p=.024). CONCLUSIONS: Birth weight can predict future cardiovascular risk profile in diverse populations. Thus, it needs to be included in targeted public health interventions for tackling the obesity pandemic and improving cardiovascular health worldwide.Key messagesThe strongest association between birth weight and later cardiovascular risk profile was manifested as differences in body mass index in two culturally and geographically distinct cohorts.Foetal growth is a determinant for later cardiovascular health in diverse populations, indicating a need to focus on maternal and foetal health to improve cardiovascular health worldwide.

Computerised emotional well-being and substance use questionnaires in young Indigenous and non-Indigenous Australian adults.

BACKGROUND: Mental health disorders rank among the most substantial causes of morbidity and mortality worldwide. Almost half of Australian adults experience mental illness at some point in their lifetime, with Indigenous Australians disproportionally affected. Thus, it is imperative that effective, acceptable screening tools are used, which are tailored to the target population. OBJECTIVES: This research investigates the methodology of computerised questionnaires in assessing the emotional well-being and substance use in Indigenous and non-Indigenous young adults. METHODS: Cross-sectional data from young adults (21-28 years) in the Life Course Program, Northern Territory, Australia, are presented. Through an extensive consultation process, validated questionnaires were adapted to a computerised format suitable for both remote and urban residing Indigenous and non-Indigenous adults. RESULTS: Of the 576 participants (459 Indigenous, 117 non-Indigenous) available for assessment, high consent rates were seen, with completion rates >86%. One in three young adults in this cohort were highlighted as 'at risk' of psychological distress, and one in five as 'at risk' of suicidal ideation or self-harm. CONCLUSION: The target population of this study were at a critical age with high levels of psychological distress and suicidal ideation reported, particularly in Indigenous young adults. This simple, user-friendly, pictorial programme allowed assessment of a sensitive topic anonymously, while simultaneously collating data and identifying those at high risk, irrespective of literacy level or cultural background.

Socioeconomic status, remoteness and tracking of nutritional status from childhood to adulthood in an Australian Aboriginal Birth Cohort: the ABC study.

OBJECTIVES: To determine prevalences of underweight and overweight as well as low and high waist-to-height ratio (WHtR) in three prospective follow-ups and to explore tracking of these measures of nutritional status from childhood to adolescence and adulthood. The influence of socioeconomic status, remoteness, maternal body mass index (BMI) and birth weight on weight status was assessed. DESIGN: Longitudinal birth cohort study of Indigenous Australians. SETTING: Data derived from three follow-ups of the Aboriginal Birth Cohort study with mean ages of 11.4, 18.2 and 25.4 years for the participants. PARTICIPANTS: Of the 686 Indigenous babies recruited to the study between 1987 and 1990, 315 had anthropometric measurements for all three follow-ups and were included in this study. PRIMARY AND SECONDARY OUTCOME MEASURES: BMI categories (underweight, normal weight, overweight and obesity),WHtR categories (low and high), sex, areal socioeconomic disadvantage as defined by the Indigenous Relative Socioeconomic Outcomes index, urban/remote residence, maternal BMI and birth weight. Logistic regression was used to calculate ORs for belonging to a certain BMI category in adolescence and adulthood according to BMI category in childhood and adolescence. RESULTS: Underweight was common (38% in childhood and 24% in adulthood) and the prevalence of overweight/obesity increased with age (12% in childhood and 35% in adulthood). Both extremes of weight status as well as low and high WHtR tracked from childhood to adulthood. Underweight was more common and overweight was less common in remote and more disadvantaged areas. Birth weight and maternal BMI were associated with later weight status. There were significant sex differences for prevalences and tracking of WHtR but not for BMI. CONCLUSIONS: Socioeconomic factors, remoteness and gender must be addressed when assessing nutrition-related issues in the Indigenous communities due to the variation in nutritional status and its behaviour over time within the Indigenous population.

Fingernail cortisol as a marker of chronic stress exposure in Indigenous and non-Indigenous young adults.

Cumulative exposure to stress over a long period can negatively impact an individual's health. Significant advancements in biomarkers of chronic stress have been made, with the use of fingernails recently explored. Cross sectional data from the Australian Aboriginal Birth Cohort (Indigenous) and Top End Cohort (non-Indigenous) were used to investigate the associations (sociodemographic and emotional) of fingernail cortisol in Indigenous and non-Indigenous young adults. Details on sociodemographic (age, gender, and Indigenous identification), smoking and alcohol use, emotional wellbeing, and emotional stress (perceived stress and stressful events), and fingernail samples were obtained face-to-face. Fingernail samples were analyzed for 179 Indigenous and 66 non-Indigenous participants (21-28 years). Indigenous participants were subjected to higher rates of stressful events compared to non-Indigenous (Median 6.0; interquartile range (IQR) 4, 9 vs. 1.0; IQR 0, 2; p < .001). Median cortisol levels were similar between Indigenous and non-Indigenous participants (4.36 pg/mg; IQR 2.2, 10.0 vs. 3.87 pg/mg: IQR 2.0, 9.7; p = .68). However, Indigenous participants had a higher cortisol level on adjustment for emotional distress and exposure to stressful events (Geometric Mean 1.82; 95CI: 1.07-3.09), with a negative association with increasing number of stressful events (Geometric Mean 0.94; 95CI 0.90, 0.99). Collection of fingernails was an easily conducted, well-tolerated method to measure stress markers in this multicultural cohort. Indigenous young adults experienced a high number of stressful events which was associated with a lowering of fingernail cortisol levels.Lay abstractChronic stress can impact negatively on health and emotional wellbeing. A fingernail sample provided a culturally acceptable, noninvasive method of measuring chronic stress in Indigenous and non-Indigenous young adults. Cortisol levels, a marker of chronic stress, were different between Indigenous and non-Indigenous young adults and were influenced by emotional status and occurrence of multiple stressful events.

Renal dysfunction is already evident within the first month of life in Australian Indigenous infants born preterm.

Antecedents of the high rates of chronic kidney disease in Australian Indigenous peoples may originate early in life. Fourteen percent of Australian Indigenous infants are born preterm (under 37 weeks gestation) and, therefore, at risk. Here, our observational cohort study sought to determine the impact of preterm birth on renal function in Australian Indigenous and non-Indigenous infants. Renal function was assessed between 4-29 days postnatally in 60 Indigenous and 42 non-Indigenous infants born at 24-36 weeks gestation. Indigenous ethnicity was associated with impaired renal function, with significantly higher serum creatinine (geometric mean ratio (GMR) 1.15 [1.06, 1.25]), fractional excretion of sodium (GMR 1.21 [1.04, 1.39]), and urine albumin (GMR 1.57 [1.05, 2.34]), ß-2 microglobulin (GMR 1.82 [1.11, 2.98]) and cystatin C (GMR 3.27 [1.54, 6.95]) when controlling for gestational/postnatal age, sex and birth weight Z-score. Renal injury, as indicated by high urine neutrophil gelatinase-associated lipocalin levels, was associated with maternal smoking and postnatal antibiotic exposure. Indigenous infants appeared to be most susceptible to the adverse impact of antibiotics. These findings show that preterm Australian Indigenous infants are highly vulnerable to renal dysfunction. Preterm birth may contribute to their increased risk of chronic kidney disease. Thus, we recommended that renal function should be closely monitored life-long in Indigenous children born preterm.

The Australian Aboriginal Birth Cohort study: socio-economic status at birth and cardiovascular risk factors to 25 years of age.

OBJECTIVES: To determine whether socio-economic status at birth is associated with differences in risk factors for cardiovascular disease - body mass index (BMI), blood pressure, blood lipid levels - during the first 25 years of life. DESIGN: Analysis of prospectively collected data. SETTING, PARTICIPANTS: 570 of 686 children born to Aboriginal mothers at the Royal Darwin Hospital during 1987-1990 and recruited for the Aboriginal Birth Cohort Study in the Northern Territory. Participants resided in 46 urban and remote communities across the NT. The analysed data were collected at three follow-ups: Wave 2 in 1998-2001 (570 participants; mean age, 11 years), Wave 3 in 2006-2008 (442 participants; mean age, 18 years), and Wave 4 in 2014-2016 (423 participants; mean age, 25 years). MAIN OUTCOME MEASURES: Cardiovascular disease risk factors by study wave and three socio-economic measures at the time of birth: area-level Indigenous Relative Socioeconomic Outcomes (IRSEO) index score and location (urban, remote) of residence, and parity of mother. RESULTS: Area-level IRSEO of residence at birth influenced BMI (P < 0.001), systolic blood pressure (P = 0.024), LDL-cholesterol (P = 0.010), and HDL-cholesterol levels (P < 0.001). Remoteness of residence at birth influenced BMI (P < 0.001), HDL-cholesterol (P < 0.001), and triglyceride levels (P = 0.043). Mother's parity at birth influenced BMI (P = 0.039). CONCLUSIONS: Our longitudinal life course analyses indicate that area-level socio-economic factors at birth influence the prevalence of major cardiovascular disease risk factors among Indigenous Australians during childhood and early adulthood.

Grip strength among Indigenous and non-Indigenous Australian adults: a longitudinal study of the effects of birth size and current size.

OBJECTIVES: Indigenous Australians are born smaller than non-Indigenous Australians and are at an increased risk of early onset of frailty. This study aimed to identify the relationship between birth size, current size and grip strength, as an early marker of frailty, in Indigenous and non-Indigenous young adults. DESIGN: Cross sectional data from two longitudinal studies: Aboriginal birth cohort (Indigenous) and top end cohort (non-Indigenous). SETTING: Participants reside in over 40 urban and remote communities across the Northern Territory, Australia. PARTICIPANTS: Young adults with median age 25 years (IQR 24-26); 427 participants (55% women), 267 (63%) were remote Indigenous, 55 (13%) urban Indigenous and 105 (25%) urban non-Indigenous. OUTCOME MEASURES: Reliable birth data were available. Anthropometric data (height, weight, lean mass) and grip strength were directly collected using standardised methods. Current residence was classified as urban or remote. RESULTS: The rate of low birthweight (LBW) in the non-Indigenous cohort (9%) was significantly lower than the Indigenous cohort (16%) (-7%, 95% CI -14 to 0, p=0.03). Indigenous participants had lower grip strength than non-Indigenous (women, -2.08, 95% CI -3.61 to -0.55, p=0.008 and men, -6.2, 95% CI -9.84 to -2.46, p=0.001). Birth weight (BW) was associated with grip strength after adjusting for demographic factors for both women (ß=1.29, 95% CI 0.41 to 2.16, p=0.004) and men (ß=3.95, 95% CI 2.38 to 5.51, p<0.001). When current size (lean mass and body mass index [BMI]) was introduced to the model BW was no longer a significant factor. Lean mass was a positive indicator for grip strength, and BMI a negative indicator. CONCLUSIONS: As expected women had significantly lower grip strength than men. Current size, in particular lean mass, was the strongest predictor of adult grip strength in this cohort. BW may have an indirect effect on later grip strength via moderation of lean mass development, especially through adolescence and young adulthood.

Examining the relationship between body mass index and adverse cardio-metabolic profiles among Australian Indigenous and non-Indigenous young adults.

Australian Indigenous young people have a 10-fold excess of deaths from ischaemic heart disease compared with non-Indigenous Australians, yet the reasons behind this remain understudied. This paper aims to describe cardio-metabolic profiles among Australian Indigenous (n = 459) and non-Indigenous (n = 117) young adults (21-27 years). The association between body size and an adverse cardio-metabolic profile (≥3 abnormal cardio-metabolic markers) is assessed by gender and urban/rural residence, employing regression analyses. The prevalence of obesity was highest among urban Indigenous participants, both males and females (22% and 23%, respectively). Overall, BMI showed a significant positive association with an adverse cardio-metabolic profile. Moreover, adverse cardio-metabolic profile was present in a substantial proportion of Indigenous participants even in overweight and normal BMI categories. Among females, this could reflect elevated waist circumference, which was present in half of those of normal weight. Remote Indigenous females had the highest predicted probability of having an adverse cardio-metabolic profile across all BMI categories (13% for underweight, 54% for normal BMI, 93% for overweight, and 99% for obese). Our findings highlight the associations between obesity and adverse cardio-metabolic profiles among Indigenous and non-Indigenous youth. Culturally-relevant strategies that address lifestyle risks, including access to healthy food, are urgently needed in this age group.

Iodine status of Indigenous and non-Indigenous young adults in the Top End, before and after mandatory fortification.

OBJECTIVE: To assess the median urine iodine concentration (UIC) of young adults in the Top End of Northern Territory, before and after fortification of bread with iodised salt became mandatory. DESIGN, SETTING: Analysis of cross-sectional data from two longitudinal studies, the Aboriginal Birth Cohort and the non-Indigenous Top End Cohort, pre- (Indigenous participants: 2006-2007; non-Indigenous participants: 2007-2009) and post-fortification (2013-15). PARTICIPANTS: Indigenous and non-Indigenous Australian young adults (mean age: pre-fortification, 17.9 years (standard deviation [SD], 1.20 years); post-fortification, 24.9 years (SD, 1.34 years). MAIN OUTCOME MEASURE: Median UIC (spot urine samples analysed by a reference laboratory), by Indigenous status, remoteness of residence, and sex. RESULTS: Among the 368 participants assessed both pre- and post-fortification, the median UIC increased from 58 µg/L (interquartile range [IQR], 35-83 µg/L) pre-fortification to 101 µg/L (IQR, 66-163 µg/L) post-fortification (P < 0.001). Urban Indigenous (median IUC, 127 µg/L; IQR, 94-203 µg/L) and non-Indigenous adults (117 µg/L; IQR, 65-160 µg/L) were both iodine-replete post-fortification. The median UIC of remote Indigenous residents increased from 53 µg/L (IQR, 28-75 µg/L) to 94 µg/L (IQR, 63-152 µg/L; p < 0.001); that is, still mildly iodine-deficient. The pre-fortification median UIC for 22 pregnant women was 48 µg/L (IQR, 36-67 µg/L), the post-fortification median UIC for 24 pregnant women 93 µg/L (IQR, 62-171 µg/L); both values were considerably lower than the recommended minimum of 150 µg/L for pregnant women. CONCLUSIONS: The median UIC of young NT adults increased following mandatory fortification of bread with iodised salt. The median UIC of pregnant Indigenous women in remote locations, however, remains low, and targeted interventions are needed to ensure healthy fetal development.

Nutritional dual burden in Indigenous young adults: The geographical differential.

OBJECTIVE: Nutritional dual burden is defined as the coexistence of underweight and overweight in the same population. We report the rates of nutritional dual burden in Indigenous young men and women in the Northern Territory. Additionally, we examine the impact geographical area has on these rates. DESIGN: Cross-sectional data obtained from the longitudinal Aboriginal Birth Cohort Study. SETTING: Participants residing in over 40 urban and remote communities across the Top End of the Northern Territory. PARTICIPANTS: Young adults aged 23-28 years; urban (n = 99) and remote (n = 316). MAIN OUTCOME MEASURE(S): Anthropometric data was directly collected using standardised methods. Underweight was defined as BMI ≤ 18.5 kg/m2 and overweight/obese as body mass index ≥ 25 kg/m2 . Remote residency was categorised by established shires/regions (Vic/Daly, Arnhem and Tiwi). RESULTS: Significantly higher levels of underweight were seen in remote participants, compared to urban participants, irrespective of sex. Further differences were seen by regions, with the highest rates seen in Vic/Daly, compared to Arnhem and Tiwi. Higher rates of overweight/obesity were found in urban participants, compared to remote. The levels of overweight/obesity varied, depending on region of residence. CONCLUSION: Underweight and overweight patterns coexist in Indigenous young adults, with variation across geographical regions. Health programs need to take this dual nutritional burden into consideration to avoid worsening the severity of underweight, whilst reducing levels of overweight.

Hair cortisol and cortisone as markers of stress in Indigenous and non-Indigenous young adults.

Chronic, ongoing stress can impact negatively on health and wellbeing. Indigenous Australians are at an increased risk of experiencing multiple stressors. Hair glucocorticoids have been used as a marker for chronic stress. This study aimed to assess the associations of hair cortisol and cortisone with sociodemographic (age, gender, Indigenous Identification), substance use, emotional wellbeing, and emotional stress, in a cohort at increased risk of stressful events and psychological distress. Cross-sectional data (age 21-28 years) are presented from two Australian longitudinal studies; the Aboriginal Birth Cohort (n = 253) and non-Indigenous Top End Cohort (n = 72). A third of the cohort reported psychological distress, with Indigenous participants reporting higher rates of stressful events compared to non-Indigenous (6 vs. 1; p < .001). Significantly higher levels of cortisone were seen in Indigenous women compared to non-Indigenous women (ß 0.21; p = .003). A positive association with age was present in hair cortisol and cortisone in Indigenous young adults (ß 0.29 and ß 0.41; p < .001, respectively). No association with substance use, emotional wellbeing or emotional stress was seen. Sub-analysis in women suggested a possible curvilinear relationship between hair cortisone and the number of stressful events. In this culturally diverse cohort, hair sampling provides a noninvasive, easily conducted and generally well tolerated mechanism to measure stress markers. The association with age, even in this narrow age range, likely represents the manifold changes in circumstances (financial independence, becoming parents, increased risk of substance use and mental illness) that occur during this transitional period of life, particularly for young Indigenous women. LAY ABSTRACT Chronic stress can impact negatively on health and emotional wellbeing. A hair sample is an easy way to measure chronic stress in Indigenous and non-Indigenous young people. The markers of chronic stress, cortisol and cortisone, were different between Indigenous and non-Indigenous, men and women and increased with age in Indigenous young adults.

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.

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

BACKGROUND: In Australia's 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.

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.

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.

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.

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.