Background: Chronic diseases in Indigenous Australians are widespread, often at rates higher than non-Indigenous Australians. The expression of chronic diseases within Indigenous Australians is not consistent across all communities reflecting differences in risk factors and health service delivery between communities. Low birth weight is recognised as a risk factor in the development of chronic disease in later life.
Data have been collected at two community wide health screens, between 1992-1996 and 2004-2006, to identify proportions of people with, and risk factors for, renal disease, cardiovascular disease and diabetes on the Tiwi Islands, Northern Territory (NT), Australia. During this interim follow up period, there has been much change in the delivery of health services in remote NT communities. Results from the first screen are described elsewhere. Data collected from the second community wide screen enables the most complete comparison of health profiles, in a relatively homogenous Indigenous community, after a 10 year follow up with significant community ascertainment at both screens.
Indigenous birth weights in the NT have been historically low. Moreover, cohorts of low birth weight infants are surviving to adulthood as a result of improved postnatal care. Global evidence suggests these individuals are at elevated risk of chronic disease development. Our group has described a relationship between low birth weight with albuminuria and blood pressure in adult females and with deaths of natural causes in the Tiwi community. Participant number and age were relatively low in those with birth weights at the first screen. However, a larger cohort with available data in the second screen has allowed a more comprehensive analysis of the relationship between birth weight and chronic disease morbidity and mortality in this high risk community.
Aims: To describe, in adults from the Tiwi community:
• Chronic disease profiles of selected diseases and their markers between 2004-2006.
• The evolution of selected chronic diseases by comparing profiles from the first health screen of 1992-1996 with the second of 2004-2006.
• The association between birth weight and chronic disease profiles from the first screen (where not previously reported) and second screen in those with recorded birth weights.
• The association between birth weight and natural terminal endpoints.
Methods: 920 and 1078 adults (≥20 years) participated in the first and second health screens between 1992-1996 and 2004-2006 respectively. Participants completed health questionnaires and underwent physical, blood and urine assessments. Data were analysed by gender in age specific groups.
Prof Hoy’s group had gathered available birth weights of babies born within the Tiwi community, and/or to a Tiwi mother, from clinic and hospital registers up to 1985. Birth weights were available for 376 and 602 adults that participated in the first and second health screen respectively.
Terminal events were obtained from the clinic death registry, which contains information regarding each death within the community, and from medical and dialysis unit records. This analysis relates to recorded deaths up to and including the 31st December 2009 in community members with recorded birth weights.
Results: In males, systolic blood pressure and serum creatinine were lower while HDL-c was higher at the second compared to the first screen. Weight, waist, BMI, diastolic blood pressure, urinary albumin and urinary creatinine were lower in middle age males at the second compared to the first screen. In older females, weight, waist and BMI were higher, total cholesterol and HDL-c lower and triglycerides higher at the second compared to the first screen. The proportions of older males and females with diabetes were significantly higher at the second compared to the first screen. Prescribed treatment for hypertension, renal disease and diabetes was highest in both older males and females at second screen.
Mean birth weight increased while rates of low birth weight decreased over time. Lower birth weights were associated with lower height, weight, waist and hip circumferences, BMI, lean mass and fat percentage in males and females, higher blood pressure in females and higher urinary ACR in males and females. In addition, blood pressure was amplified by the cumulative effect of lower birth weight and higher adult BMI in males and females. Lower birth weight was associated with higher rates of death due to natural causes.
Conclusions: This thesis presents the most comprehensive follow-up of chronic disease profiles in any Aboriginal community over time. It also provides the most complete description of the association between birth weight and chronic disease morbidity and mortality in remote living Indigenous Australians. These results have profound implications for remote health service delivery. Chronic disease screening must occur regularly, at least, in adolescence and must be comprehensive in nature by screening for multiple instead of single conditions. Special attention should be given to two groups: 1) those of low birth weight to avoid the amplifying effects of obesity on disease occurrence and 2) young Indigenous women with a specific focus on antenatal care.