Renal disease in the Aboriginal community of Woorabinda
Peter S. Hill, School of Population Health, The University of Queensland, Herston Road, Herston, Queensland, 4006, Australia. Email: email@example.com
Objective: An apparent increase in the incidence of end-stage renal disease had been observed in the Australian Aboriginal community of Woorabinda. This study documents the incidence of end-stage renal disease (ESRD) in Woorabinda, and correlates this with predictors of renal disease.
Design: The methodology included a retrospective audit of deaths from, and cases commencing treatment for ESRD between 1999 and 2001 in Woorabinda, and a cross-sectional study.
Participants: The 183 participants were Aboriginal residents over 15 years of age. Females numbered 102 (55.7%) and males 81 (44.3%).
Main outcome measure: The incidence of ESRD was comparable to other recognised high incidence Indigenous communities in Australia. This was corroborated by a high prevalence of predictors of renal disease.
Results: Audit: the year 2001 age- and sex-standardised incidence ratio for commencement of renal replacement therapy is 93.18 (95% CI, 25.34–238.53). Clinical Study: the prevalence of overt albuminuria was 7.6%; 11.7% had an albumin : creatinine ratio >3.4–33.9 g mol−1; 33.3% had microalbuminuria of ≥20 mg L−1; and 67.8% prevalence of proteinuria was found. The prevalence of diabetes was 18.6%, with another 13.2% having impaired fasting glucose. There was a 19.7% prevalence of hypertension. Of those with hypertension 22.2% had overt albuminuria.
Conclusions: Although Woorabinda was previously placed in a region of low end-stage renal disease incidence, further investigation has identified a high incidence of renal disease, not exclusively due to diabetes. The finding raises questions regarding the current trajectory of the epidemic in other Aboriginal and Torres Strait Islander communities.
End-stage renal disease (ESRD) is an increasingly recognised problem for Indigenous and minority groups in the ‘fourth world’. In the USA the burden of renal disease is carried disproportionately by African and Native Americans1 and Mexican Americans.2 In Canada an excess of renal disease has been observed among Native Americans,3 and in Australia regional epidemics of renal disease have been identified among Torres Strait Islander and Aboriginal populations.4
In 2001, a systematic report was conducted to determine variation in the incidence of ESRD among Indigenous Australians across the 36 Aboriginal and Torres Strait Islander Commission (ATSIC) regions between 1993 and 1998.5 The remote areas of Tennant Creek, Aputula and Jabiru in the Northern Territory, Warburton and Kalgoorlie in Western Australia, and Ceduna in South Australia were found to have the highest incidence of ESRD with up to 1300 cases per million.
The ATSIC region of Rockhampton was identified as being among the regions of lowest incidence with less than 100 per million. Woorabinda is a rural Aboriginal community of 961 people located within the Rockhampton ATSIC region.6 Local anecdotal evidence, however, suggested a rise in the rate of ESRD, and a clinical study and retrospective audit were conducted to examine the current pattern of renal disease in Woorabinda.
What is already known on this subject:
- • Although renal disease has been recognised in Aboriginal and Torres Strait Islander communities, the areas of high incidence were limited and well recognised.
- • On the basis of a systematic review in 2001, Woorabinda community, the locus of this study, was located within a region of lowest incidence of end-stage renal disease.
What this study adds:
- • This study conducted an audit of end-stage renal disease from 1999 to 2001, which demonstrates levels comparable with the regions of highest reported incidence. The evidence is corroborated with high levels of serum predictors of renal disease, obtained through voluntary screening.
- • The study raises questions regarding the trajectory of the epidemic of renal disease in Aboriginal and Torres Strait Islander communities, given the unpredicted rise of end-stage renal disease and the high incidence of renal disease predictors in Woorabinda community.
The study comprises two elements: an audit of ESRD and a clinical study of the incidence of predictors of renal disease.
The audit is a retrospective review of the incidence of ESRD for the years 1999–2001. The audit includes all cases of ESRD treated at the sole health care provider in the community – the Woorabinda Multipurpose Health Service. Cases of ESRD are defined as those who received renal replacement therapy or died of ESRD. The limitations of such studies in communities with low populations are acknowledged.
The clinical study investigates the prevalence of predictors of renal disease in the Woorabinda community, undertaken during community clinical screening conducted by the Woorabinda Health Service in December 2001. The clinical factors relevant to renal disease included blood pressure, diagnosed diabetes, fasting blood glucose, Hba1c, proteinuria, microalbuminuria, albumin : creatinine ratio (ACR), serum urea and serum creatinine.
Blood pressure was measured following 5-min rest (using the ‘Dinamap Plus Vital Sign Monitor’). Fasting blood glucose, Hba1c, serum urea and serum creatinine were determined from fasting blood specimens, and proteinuria, microalbuminuria and ACR were determined by spot urine specimens, analysed by Queensland Health Pathology and Scientific Services.
Diabetes status was determined by participant self-report and confirmed by clinical record. New cases of diabetes were determined by a fasting blood glucose ≥7.0 mmol L−1.7 Impaired fasting glucose (IFG) is defined as a fasting blood glucose of ≥5.5 and <7 mmol L−1.7
Overt albuminuria was determined by an ACR of ≥34 g mol−1. Microalbuminuria was determined as an ACR >3.4–33.9 g mol−1 as well as by urine biochemistry of ≥20 mg L−1. Proteinuria was determined by urine biochemistry of ≥100 mg L−1.
Ethical approval was provided by the Rockhampton Health District Human Research Ethics Committee. Permission to publish the study findings has been granted by the Woorabinda Aboriginal Council.
The 183 participants in the clinical screening were volunteers over 15 years of age, who had fasted for the previous 10 h. The screened population represents approximately one-third of the total adult population of 579.6 The sex distribution of the screened population was female: 55.7% (n = 102) and male: 44.3% (n = 81). The age correlation between the screened population and the 2001 Australian Bureau of Statistics population data is r = 0.91 (P < 0.001) and the sample is considered representative of the total adult population of Woorabinda.
In 1999 the unstandardised incidence of ESRD in Woorabinda was 2081 per million, and in 2000 and 2001 it was 5203 per million. Using the 2000 Australian figures of the Australia and New Zealand Dialysis and Transplant Registry (ANZDATA) 2001 Report8 and indirect standardisation to calculate the age- and sex-standardised incidence ratio for commencement of ESRD treatment for people of Woorabinda in 2001, the standardised incidence ratio is 93.18 (95% CI, 25.34–238.53).
There is a high prevalence of diabetes with 18.6% having known diabetes or a fasting blood glucose of ≥7.0 mmol L−1. 13.2% of those screened were found to have possible diabetes with an IFG between ≥5.5 and <7.0 mmol L−1.
Overt albuminuria (ACR ≥ 34 g mol−1) was found in 7.6% of the screened population. Of those with overt albuminuria (ACR = 34 g mol−1) 92.3% had diabetes (mean, 214.17, standard deviation, 167.99; P < 0.001).
A 67.8% prevalence of proteinuria (≥100 mg L−1) was found, but there does not appear to be a relationship between diabetes status and prevalence of proteinuria (chi-squared: P > 0.1), although the severity of the proteinuria is greater in those with diabetes. There is a significant difference in the mean proteinuria between the diabetes status categories (anova: P < 0.01).
There was a prevalence of microalbuminuria of 11.7% of ACR >3.4–33.9 g mol−1. The prevalence of microalbuminuria (≥20 mg L−1) was 33.3% and a significant difference was found in prevalence between the categories of diabetes status (chi-squared: P < 0.005).
The prevalence of hypertension was found to be 19.7%, with 38.9% of those with hypertension diagnosed as diabetic and 25% with possible diabetes (chi-squared: P < 0.05). Of those with hypertension 22.2% had overt albuminuria.
Woorabinda is located within the Rockhampton ATSIC region, found to be one of the lowest ESRD incidence ATSIC regions in a study conducted between 1993 and 1998.5
However, between 1999 and 2001, there were 12 cases of ESRD in the Woorabinda population of 961.6 The unstandardised incidence of ESRD in Woorabinda for the years 2000 and 2001 is 5203 per million, compared with the 2700 per million incidence of ESRD among the Tiwi Island communities.9
The highest standardised incidence ratio for ESRD for Indigenous people in an ATSIC region (using indirect standardisation to adjust for sex and age), was 31.05 (95% CI, 20.96–44.33).5 When the 2001 treated cases of ESRD in Woorabinda are adjusted for age and sex using indirect standardisation, the standardised incidence ratio is 93.18(95% CI, 25.34–238.53).
Clearly, despite being previously located in a low incidence area for ESRD, the observed incidence of ESRD in Woorabinda is now comparable with other high incidence Indigenous populations.
Possible explanations for the increase could include under-reporting in the original ANZDATA records, or improved access to treatment (and therefore inclusion in the ANZDATA) since the 1993–1998 study. The establishment of an integrated health service, with improved continuity of medical care and a Diabetes Educator, contributed. The third possibility is that Woorabinda is experiencing a sudden and significant increase in ESRD, as in other Indigenous or disadvantaged groups.1,10–12
The community screening revealed a high prevalence of diabetes (18.6%), with an additional 13.2% with possible diabetes (IFG). Estimates for the Australian national prevalence of diabetes range from 4.3% to 7.4%;13,14 and prevalence of IFG is 16.4%.14 The overall prevalence of diabetes among Australian Aboriginal people and Torres Strait Islanders is estimated to be 10–30%.15
Although diabetes is known to contribute to much renal disease in Aboriginal communities, the predictors of renal disease not associated with diabetes are also of interest. The Woorabinda community screening demonstrated a high prevalence of microalbuminuria (11.7% ACR >3.4–33.9 and 33.3% microalbuminuria ≥20 mg L−1). ACR >3.4–33.9 was found in 20.6% of those with diabetes. Overt albuminuria as measured by ACR of ≥34 g mol−1 was found in 7.6% of the Woorabinda adult population and in 30.5% of those with diabetes. There was a 67.8% prevalence of proteinuria as measured by proteinuria of ≥100 mg L−1, although the protocol did not exclude sexually transmitted infections, urinary tract infections, nor menstruation.
The prevalence of 19.7% hypertension in Woorabinda is slightly higher than the Australian national prevalence.16 Hypertension is twice as prevalent in diabetes compared with non-diabetic individuals.17,18 There was a high prevalence of overt albuminuria (22.2%) in those with hypertension.
Of the 12 people in Woorabinda to develop ESRD in the three-year audit period only one did not have diabetes, with non-diabetic nephropathy confirmed through renal biopsy. Of the 11 diabetics, the clinical presentation was consistent with diabetic nephropathy and renal biopsies were not performed. In Woorabinda there appears to be a strong association between the indicators of renal disease and diabetes; however, the 62.9% prevalence of proteinuria of ≥100 mg L−1 (mean, 243.7, standard deviation, 273.33) and 9.7% ACR >3.4–33.9 g mol−1 among the diabetes unlikely category is predictive of renal disease independent of diabetes.
The increased incidence of renal disease among Indigenous people has serious implications for resource allocation associated with case management and community-based intervention. The epidemic of renal disease among Australian Aboriginal people shows a doubling of the incidence rate every four years.9,19 The escalation in the incidence of ESRD in Woorabinda appears consistent with this observation. The association between microalbuminuria and overt albuminuria and cardiovascular complications augurs a considerable health and financial burden.
Despite its earlier classification in a low incidence ESRD region, the retrospective audit and community clinical assessment have identified an escalation in renal disease in Woorabinda similar to that seen in the other Indigenous peoples, raising questions as to the current trajectory of this epidemic in other rural Aboriginal and Torres Strait Islander communities.
The ‘Impact of Traditional Lean Meat and Exercise Interventions on Diabetes and Cardiovascular Disease Risk Factors’ research project (part of which is this research) is funded by the National Health and Medical Research Council (Australia) and Queensland Health. The authors wish to acknowledge the support of Rhylla Webb as Director of Nursing and the important contribution to this research by the following members of the Community Health Team of the Woorabinda Multipurpose Health Service: Lloyd Savage, Joshua Weazel, Lorna Vaggs, Maurice Barry, Felicity Gulf, Valerie Tye, Darryl Smith, June Barkworth and Anne Dunne.