Chronic kidney disease and cardiovascular disease in Aboriginal children and young adults

Abstract

Introduction Addressing the gap in health between Aboriginal and Torres Strait Islander and non-Indigenous Australians is a national health priority. The life expectancy of Aboriginal and Torres Strait Islander Australians is currently 70 years for males and 74 years for females, which is 10 years lower than that of non-Aboriginal Australians. Around 80% of the mortality gap is attributable to chronic disease across all ages, with cardiovascular diseases specifically accounting for around 24% of the mortality gap. Aboriginal and Torres Strait Islander Australians have a higher prevalence of cardiovascular disease (27% vs 21%), diabetes (18% vs 5%) and chronic kidney disease (22% vs 10%), with Aboriginal and Torres Strait Islander showing higher prevalence of these conditions during early adult life. Rates of end stage kidney disease are five-fold higher among Aboriginal and Torres Strait Islander Australians compared to non-Indigenous Australians. Cardiovascular disease, diabetes and chronic kidney disease have a number of shared risk factors such as obesity, smoking, hypertension, diet and physical activity as well as perinatal risk factors such as low birth weight. Almost all studies investing the prevalence of risk factors for chronic disease have been cross sectional, with very few having tracked the risk of developing chronic kidney disease through childhood and adolescence into adult life. The Antecedents of Renal Disease in Aboriginal Children (ARDAC) is a population based long-term cohort study, the details of which have been published previously. Commenced in 2002, at an average age of 8.9 years, the original cohort of ARDAC participants has been followed up through mid-childhood, and at four years of follow up (at an average age of 13.3 years) no differences in the prevalence of albuminuria, high systolic blood pressure or obesity between Aboriginal and non-Aboriginal children were observed. The overarching hypothesis of my doctoral research is the higher prevalence of chronic disease in Aboriginal people becomes evident in adolescence and early adult life, and that this inequity is largely explained by the social determinants of health. The aims of my doctoral research was to extend the follow up of the ARDAC Study to 10 years (mean age 16 years), and compare the prevalence of albuminuria and change in blood pressure and body mass index (BMI) from childhood to adolescence using a longitudinal approach to data analysis. I also investigated the influence of the risk factors of residential remoteness, socioeconomic status and birth weight on these early indicators of adult chronic disease. I also aimed to further investigate the influence of the social determinants of health on the incidence of chronic kidney disease through a systematic review of the literature and meta-regression analysis. Finally I aimed to investigate the prevalence of obesity and hypertension in young people in the general Australian population though use of the microdata available from the Australian Health Survey, and to identify behaviour risk factors for hypertension and obesity. Beginning the trajectory to ESKD in adult life: Albuminuria in Australian Aboriginal children and adolescents Globally, disadvantaged populations suffer a high burden of chronic kidney disease. The trajectory to chronic kidney disease during childhood and adolescence remains unclear due to a paucity of longitudinal studies. 3418 participants (1469 non-Aboriginal and 1949 Aboriginal) were enrolled in a prospective, population based cohort study at participating schools across New South Wales (NSW), Australia since 2002. Albumin: creatinine ratio was measured by dipstick every two years along with body mass index (BMI), blood pressure. We used multivariable logistic generalised estimating equation models to examine if Aboriginal children had a higher prevalence of albuminuria compared with non-Aboriginal children with increasing age, and to identify potential risk factors. At enrolment with a mean age of 10.6 years, 14.2% of children were obese and 16.0% overweight, and 11.5% were found to have albuminuria. Over 8 years (11,387 participant-years) of follow up the prevalence of albuminuria increased to 18.5%, overweight to 16.1% and obesity to 17.2%. BMI standard deviation score (SDS) was found to have a differential effect on the risk of albuminuria in Aboriginal and non-Aboriginal children (P interaction < 0.01). The prevalence of albuminuria decreased as BMI SDS increased in both groups of children, but more in non-Aboriginal children, leading to a 2.5% higher prevalence of albuminuria in overweight Aboriginal children (95 CI%: 1.0 to 4.2%). Compared with non-Aboriginal children, Aboriginal children are of higher risk of albuminuria when overweight or obese. These findings suggest that interventions to reduce the prevalence of overweight and obesity, particularly in adolescence and early adult life, are of critical importance to reduce the higher burden of chronic kidney disease experienced by Aboriginal Australians. The differential effect of socioeconomic status, birth weight and gender on body mass index in Australian Aboriginal Children Adult Aboriginal Australians have 1.5 fold higher risk of obesity but the trajectory of body mass index (BMI) through childhood and adolescence and the contribution of socioeconomic factors remain unclear. Our objective was to determine the changes in BMI in Australian Aboriginal children relative to non-Aboriginal children as they move through adolescence into young adulthood, and to identify risk factors for higher BMI. A prospective cohort study of Aboriginal and non-Aboriginal school children commenced in 2002 across 15 different screening areas across urban, regional and remote New South Wales, Australia. Socio-economic status was recorded at study enrolment and participants’ BMI was measured every 2 years. We fitted a series of mixed linear regression models adjusting for age, birth weight and socioeconomic status for boys and girls. 3418 (1949 Aboriginal) participants were screened over a total of 11,387 participant years of follow up. The prevalence of obesity was 14.2% (mean age 11 years) at baseline, and increased to 17.2% by a mean age of 16 years. The mean BMI increased with age and was significantly higher among Aboriginal girls compared to non-Aboriginal girls (P<0.01). Girls born at low birth weight had a lower BMI than girls born of normal birth weight (P<0.001). Socioeconomic status and low birth weight had a differential effect on BMI for Aboriginal boys compared to non-Aboriginal boys (P for interaction = 0.01). Aboriginal boys of highest socioeconomic status, unlike those of lower socioeconomic status, had a higher BMI compared to non-Aboriginal boys. Non-Aboriginal boys of low birth weight were heavier than Aboriginal boys. Socioeconomic status and birth weight have differential effects on BMI among Aboriginal boys, and Aboriginal girls had a higher mean BMI than non-Aboriginal girls through childhood and adolescence. Intervention programs need to recognise the differential risk for obesity for Aboriginal and non-Aboriginal boys and girls to maximise their impact. Blood pressure in Aboriginal and non-Aboriginal children through childhood and adolescence Hypertension is associated with an increased risk of chronic kidney disease (CKD) in adulthood. Aboriginal adults have a higher prevalence of hypertension, but whether this develops during childhood and adolescence is unclear. Our aim was to determine relative changes in blood pressure between Aboriginal and non-Aboriginal children as they move through adolescence into young adulthood. A prospective cohort study of Aboriginal and non-Aboriginal schoolchildren commenced in 2002 across NSW. Blood pressure was measured every 2 years. We fitted a series of mixed linear regression models for systolic and diastolic blood pressure adjusting for age, sex, Aboriginality, birth weight and socioeconomic status (SES). 3418 (1949 Aboriginal) participants were screened over a total of 11, 387 participant years follow up. At study enrolment at a mean age of 11 years, , the prevalence of high systolic blood pressure (SBP SDS > 95th centile) was 7.2% which increased to 15.4% at eight years follow up (mean age was 15.36 years). Although age and birth weight had a differential effect on systolic blood pressure for Aboriginal boys, the difference in systolic blood pressure was minor. The was no difference in the systolic blood pressure of Aboriginal girls compared to non-Aboriginal girls. For both boys and girls, lower socioeconomic status was associated with an increase in systolic blood pressure of approximately 2.5 mmHg. The prevalence of high diastolic blood pressure was approximately 3% for both boys and girls and remained constant over follow up. Socioeconomic status had a differential effect on blood pressure for Aboriginal children, with lower socioeconomic status associated with lower diastolic blood pressure for both boys and girls. The prevalence of high systolic blood pressure increased through adolescence, with no difference in systolic blood pressure for Aboriginal participants compared to non-Aboriginal participants. Low socioeconomic status is associated with an increase in systolic blood pressure among children and adolescents, and targeted intervention for young people of low socioeconomic status is required to control blood pressure within our community. The social determinants of chronic kidney disease: a systematic review Socio-economic disadvantage is increasingly recognised as an important risk factor for chronic disease, but the strength of the association with the development of chronic kidney disease (CKD) and the contribution of the various domains of disadvantage are uncertain. The aim of this study was to synthesise the evidence regarding the risk of CKD and end stage kidney disease (ESKD) in the general population according to markers of socio-economic disadvantage. We performed a systematic review and meta-analysis of published primary articles in MEDLINE, EMBASE or CINAHL (until December 2014), risk of bias was assessed using the Newcastle Ottawa Scale and summary effects were estimated using random effects meta-analysis and meta-regression. Cohort studies conducted in the general population and the social determinants of health investigated were ethnicity, education, income, occupation and area level measures of socio-economic status with the outcome of interest incident CKD (any stage). We identified 21 studies (n=12,987,147) - 13 investigated risk by ethnicity, education (9), income (6), area level socio-economic status (4) and occupation (2). Only two of the included studies were of high risk of bias. Black Americans have more than double the risk of ESKD compared to white Americans (hazard ratio 2.33, 95% confidence interval 2.02 to 2.63, I2 59%). Low income was found to increase risk of ESKD in four of the six studies identified, however low education and low SES were not consistently identified as risk factors for CKD. Measurement of domains, and thresholds used to define disadvantage were heterogeneous so that summary estimates were generally not able to be calculated. Although there is a substantial body of evidence regarding the association between socioeconomic disadvantage and CKD, there appears to be an inconsistent relationship. This may be artefactual, due to difficulties in quantifying disadvantage, or reflect true underlying differences in the association across different settings. Obesity and hypertension in Australian young people: Results from the Australian Health Survey 2011 to 2012 Few studies have focused on the prevalence of hypertension and obesity among young people (ages 15 to 25), although there is increasing awareness that preventative programs need to target this age group. We examined the prevalence of overweight, obesity and hypertension among 2 163 young people in Australia using data from the Australian Health Survey 2011 to 2012 and aimed to identify behavioural risk factors using logistic regression. The prevalence of obesity increased from 7.5% to 15% through the ages of 15 to 25 among boys, whilst the prevalence of overweight and obesity remains constant among girls throughout this age group (14%). Low levels of physical activity was shown to be a strong risk factor for obesity for both boys (odds ratio 5.95, 95% CI 1.83 to 19.36) and girls (OR 3.20 95% CI 0.69 to 14.87). Low socioeconomic status was associated with obesity among girls only. Although the prevalence of hypertension is low in this age group, the prevalence of high normal blood pressure is high especially among men (28% men and 14% women). Our results suggest that programs targeting physical activity participation should be tailored differently for boys and girls, with a focus on girls during late childhood and early adolescence but late adolescence and early adult life for boys.