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End-stage renal disease in Aboriginals in New South Wales: a very different picture to the Northern Territory

Alan Cass, Adrian G Gillin and John S Horvath
Med J Aust 1999; 171 (8): 407-410.
Published online: 18 October 1999
Research

End-stage renal disease in Aboriginals in New South Wales: a very different picture to the Northern Territory

Alan Cass, Adrian G Gillin and John S Horvath

MJA 1999; 171: 407-410

Abstract - Introduction - Methods - Results - Discussion - Acknowledgements - References - Authors' details
- - More articles on Aboriginal health


Abstract Objectives: To compare the incidence of end-stage renal disease (ESRD) among Aboriginals in New South Wales with the incidence among Aboriginals in the Northern Territory, and to compare the patterns of ESRD among Aboriginals and non-Aboriginals in NSW.
Design: Secondary data analysis of information from unpublished and published Australia and New Zealand Dialysis and Transplant Registry reports.
Main outcome measures: Average annual incidence of ESRD (persons per million); form of renal replacement therapy; mortality at 31 March 1998; patient and graft survival one and five years after transplant.
Results: Each year in NSW, 5-17 new Aboriginal patients are treated for ESRD. There was no increase in the average annual incidence of ESRD among NSW Aboriginals (118 per million in 1988-1989 and 111 per million in 1996-1997), whereas incidence in the NT increased from 255 per million to 800 per million. In NSW, ESRD was attributed to diabetes in 32% of Aboriginal patients, compared with 13% of non-Aboriginal patients (P < 0.001). In NSW, Aboriginal patients were younger and more likely to be female, a pattern similar to that in the NT. The outcome of ESRD treatment is not significantly different between Aboriginals and non-Aboriginals in NSW.
Conclusion: There is a different pattern of incidence of ESRD and of outcomes with treatment among Aboriginals in NSW compared with those in the NT. A possible explanation is that the lower incidence in NSW reflects less profound socioeconomic disadvantage and better access to primary and specialist care.


Introduction Indigenous Australians experience high morbidity and mortality due to end-stage renal disease (ESRD). In the Northern Territory, the average annual incidence of ESRD for Aboriginals in 1988-1993 was 17.4 times that for non-Aboriginals,1 a disparity made more apparent by age adjustment.2 The number of dialysis treatments in the NT is doubling every two years.3

The 30 June 1996 estimate of the Indigenous population (386 049) represented 2.1% of the total Australian population,4 but Aboriginals constitute 5% of the Australian members of the Australia and New Zealand Dialysis and Transplant Registry (ANZDATA).5 Whether the increasing incidence and prevalence of renal disease is occurring in NSW as well as nationally and in the NT has not been well documented.

The aims of our study were to document the number of new Aboriginal patients with ESRD in NSW during 1987 to 1998 and compare recent trends in incidence with national and NT data, and to compare for Aboriginal and non-Aboriginal patients in NSW:

  • the patterns of aetiology of ESRD;

  • the demographic characteristics at the time of being entered into ANZDATA;

  • the outcomes for individuals who were notified to the Registry during the period 1987 to 1998; and

  • patient and graft survival for those who received transplants during the period 1987 to 1998.


Methods Information was obtained from ANZDATA Annual Reports (12 and 18-21)6-10 and unpublished data from ANZDATA. All nephrology units in Australia and New Zealand that provide dialysis or transplant services submit detailed six-monthly reports to ANZDATA. The reports give information regarding new patients accepted onto treatment programs, deaths that have occurred, and any alteration in treatment for current patients, including changing the mode of dialysis or receiving a transplant.

For NSW, the NT and across Australia, we analysed:

  • the number of Aboriginal patients entered into ANZDATA from 1987 to 1998 in NSW, the NT and across Australia; and

  • the average annual incidence of ESRD.

For NSW only, we analysed:

  • primary renal disease diagnostic category;

  • mean age;

  • outcome data at 31 March 1998 for people who had been entered into ANZDATA since 1 January 1987. Outcomes were categorised as death, functioning transplant, haemodialysis, continuous ambulatory peritoneal dialysis (CAPD), and loss to follow-up or having moved interstate;

  • causes of death, categorised into cardiac, vascular, infection, social, malignancy and other;

  • patient survival and graft survival for transplants performed between 1 January 1987 to 31 March 1998.

The average annual incidence of ESRD was calculated using Australian Bureau of Statistics (ABS) estimates and projections of the Aboriginal and Torres Strait Islander population for the years between actual Census counts. These estimates are based upon current trends in fertility and mortality and take into account an increasing propensity for people to identify themselves as being of Indigenous origin. The definition of "Aboriginality" from both data sources (ANZDATA and ABS) relies upon self-identification. Annual incidence was calculated as an average for each two-year period, as there is marked variability in the number of new patients per year, and small absolute numbers.

Statistical analysis of demographic and outcome data was performed using STATA 5.0.11 A t test of means and χ2 test or Fisher's exact test of proportions were performed. Survival analysis was performed at the ANZDATA Registry. Data were provided as actuarial life-table estimates and the log rank test was performed. The data were entered into STATA 5.0 and graphed.


Results  

Incidence Each year in NSW, 5-17 new Aboriginal patients are treated for ESRD (Table 1). The average annual incidence of ESRD among Aboriginals in NSW for the two years 1988-1989 was 118 per million. This remained substantially unchanged at 111 per million in 1996-1997. During the same period the average annual incidence of ESRD in Aboriginals across Australia increased significantly (Table 1); in the NT, the rise in incidence was more marked. The crude incidence for non-Aboriginals in NSW was 78 per million for 1993-1997, a slight rise from the 1980s due to increased acceptance for dialysis of patients over the age of 65 years.

Diagnostic categories
Diabetes, glomerulonephritis and hypertension are the most common primary renal diseases among Aboriginals with ESRD in NSW (Table 2). Diabetes is listed as the primary renal disease in 32% of Aboriginals, compared with 13% of non-Aboriginals (P < 0.001). Analgesic nephropathy affects a significantly greater proportion of the non-Aboriginal population, mainly among females: 28% in non-Aboriginal females, compared with 10% in Aboriginal females. No definite diagnosis was recorded for 11% of Aboriginals, compared with 5% of non-Aboriginals (P = 0.004).

Demographics Significantly more Aboriginal females than males entered the ESRD program in NSW (Table 3), the reverse pattern to non-Aboriginals (P = 0.03). The Aboriginal population was younger at entry to the program and there were significantly fewer people over the age of 65 years (P < 0.001). Outcome, or patient status at 31 March 1998, was not significantly different between the groups (P = 0.59). However, no attempt at age or sex standardisation has been made in this analysis.  

Causes of death
The differences between Aboriginals and non-Aboriginals in NSW in causes of death approach statistical significance (P = 0.07). A significantly larger proportion of Aboriginals died from cardiovascular diseases (P = 0.01). A significantly smaller proportion of deaths were due to social reasons (P = 0.02).

Patient and graft survival after transplant
Aboriginal patients receiving transplants in NSW during the study period were younger (Figure 1), but experienced lower patient survival and graft survival rates (Figures 2a and 2b), although these differences were not significant (Table 4).


Discussion Our data show no evidence of an epidemic of renal failure among Aboriginals in NSW, although the incidence remains higher than among the non-Aboriginal population. Aboriginal patients in NSW with ESRD are on average 10 years younger than non-Aboriginal patients, more likely to be female, and more likely to have diabetes and to die of cardiovascular disease. These features are similar to those reported in the NT.2 However, in NSW, there is no significant difference in outcome between Aboriginal and non-Aboriginal patients who have been entered into the Registry since January 1987, whereas, in the NT, survival is significantly worse in Aboriginal than in non-Aboriginal patients.2 The persistently high rate of withdrawal up to 1997 of NT Aboriginal people from ESRD treatment, about 25%,3 is not present in NSW.

Our results show that diabetes, glomerulonephritis and hypertension are the prominent primary causes of ESRD among NSW Aboriginals. The rise in renal failure attributed to diabetes follows a similar pattern to that noted in Aboriginals across Australia.10 The pattern of primary causes of renal disease is consistent between Aboriginal populations in different States.10

Impediments to effective and culturally appropriate service delivery to Aboriginal patients have been postulated as reasons for poor survival and high withdrawal rates from treatment.12 Therapeutic programs have typically removed people from their cultural and social support networks by requiring patients to leave their land, families and communities.13 Unlike in the NT, South Australia and Western Australia, there are few remote, non-urbanised communities in NSW; Aboriginals in NSW reside predominantly in cities and rural towns.

The higher proportion of Aboriginal patients with uncertain aetiology of their ESRD is consistent with a lower renal biopsy rate, which may relate to late referral and lack of access to renal specialist services. In NSW, specialist renal services are increasingly being provided where Aboriginals live. The Statistical Local Areas with the highest proportion of Indigenous people are Brewarrina (53.1%), Central Darling (25.3%), Bourke (24.5%) and Walgett (20.4%).14 CAPD training is now occurring in some larger rural centres, and haemodialysis facilities are provided in Bourke and Brewarrina. These initiatives, which significantly reduce the dislocation of patients from their community and remove impediments to the delivery of appropriate ESRD services, may facilitate improved survival.

There is a tendency towards lower patient survival and graft survival among NSW Aboriginals compared with non-Aboriginals, despite the Aboriginal graft recipients' being younger. In the NT, graft and patient survival among Aboriginals are significantly worse at one and five years than among non-Aboriginals.2 A significant difference in survival is not evident in the NSW data. The larger 95% confidence intervals in the NSW Aboriginal group are a consequence of fewer transplants being performed: 36 among Aboriginal patients, compared with 1755 among non-Aboriginal patients. These numbers do not provide sufficient power to detect a significant difference between the groups.

The pattern of rapidly increasing incidence of ESRD among Aboriginals across Australia, especially in the NT, is not seen in NSW. Spencer et al argue that the increase in the NT is real, not due to ageing of the Aboriginal population or improved ascertainment.2 The reason for this difference in incidence is not clear. It may be due to differences between the populations in apparent predisposition to renal disease or to differences in the prevalence of primary causes and promoters of chronic renal disease. The epidemic of disease in the NT is not only due to an increased prevalence of diabetes. Community screening studies show a prevalence of significant proteinuria in marked excess of the prevalence of diabetes or impaired glucose tolerance.2,15 In the NT, from 1988 to 1993, the average annual incidence of ESRD not attributable to diabetes was 350 per million per year among Aboriginals.1 Lower incidence of ESRD in NSW Aboriginals may reflect less profound socioeconomic disadvantage and readier access to effective primary and specialist care. However, there may be poor ascertainment, particularly in rural areas of NSW. Further study is indicated to analyse this question.



Acknowledgements
The data reported here have been supplied by the Australia and New Zealand Dialysis and Transplant Registry. The interpretation of these data is the responsibility of the authors and in no way should be seen as an official policy or interpretation of the Australia and New Zealand Dialysis and Transplant Registry. Dr Alan Cass is the recipient of a postgraduate research scholarship from the Centre for Kidney Research, New Children's Hospital, Sydney. We thank Dr Wendy Hoy, who critically reviewed the manuscript, and Dr Zhiqiang Wang, who provided statistical advice.


References
  1. Hoy WE, Mathews JD, Pugsley DJ. Treatment of end-stage renal disease in the Top End of the Northern Territory: 1978-93. Nephrology 1995; 1: 307-313.
  2. Hoy WE, McFarlane R, Pugsley DJ, et al. Markers for cardiovascular and renal morbidity: expectations for an intervention programme in an Australian aboriginal community. Clin Exp Pharmacol Physiol 1996; 23: S33-S37.
  3. Spencer JL, Silva DT, Snelling P, Hoy WE. An epidemic of renal failure among Australian Aboriginals. Med J Aust 1998; 168: 537-541.
  4. Australian Bureau of Statistics. Experimental estimates of the Aboriginal and Torres Strait Islander population. Canberra: ABS, 1998. (Catalogue No. 3230.0.)
  5. Disney AP. Demography and survival of patients receiving treatment for chronic renal failure in Australia and New Zealand: report on dialysis and renal transplantation treatment from the Australia and New Zealand Dialysis and Transplant Registry. Am J Kidney Dis 1995; 25: 165-175.
  6. Disney APS, Collins J, Russ GR, et al. ANZDATA Registry Report 1989. Adelaide: Australia and New Zealand Dialysis and Transplant Registry, 1989.
  7. Disney APS, Collins J, Russ GR, et al. ANZDATA Registry Report 1995. Adelaide: Australia and New Zealand Dialysis and Transplant Registry, 1995.
  8. Disney APS, Collins J, Russ GR, et al. ANZDATA Registry Report 1996. Adelaide: Australia and New Zealand Dialysis and Transplant Registry, 1996.
  9. Disney APS, Collins J, Russ GR, et al. ANZDATA Registry Report 1997. Adelaide: Australia and New Zealand Dialysis and Transplant Registry, 1997.
  10. Disney APS, Collins J, Russ GR, et al. ANZDATA Registry Report 1998. Adelaide: Australia and New Zealand Dialysis and Transplant Registry, 1998.
  11. STATA statistical software [computer program]. Version 5.0. College Station, Texas: Stata Corporation, 1997.
  12. Bennett E, Manderson L, Kelly B, Hardie I. Cultural factors in dialysis and renal transplantation among aborigines and Torres Strait Islanders in north Queensland. Aust J Public Health 1995; 19: 610-615.
  13. Willis J. Fatal attraction: do high technology treatments for end-stage renal disease benefit aboriginal patients in central Australia? Aust J Public Health 1995; 19: 603-609.
  14. Australian Bureau of Statistics. Census of population and housing -- selected social and housing characteristics for statistical local areas, New South Wales and Jervis Bay. Canberra: ABS, 1996. (Catalogue no. 2015.1.)
  15. Van Buynder PG. The epidemiology of renal disease in Aboriginal Australians [Master of Public Health thesis]. Sydney: University of Sydney, 1991.

(Received 12 Feb, accepted 19 Jul, 1999)


Authors' details Menzies School of Health Research, Darwin, NT.
Alan Cass, MB BS, FRACP, PhD student.

Department of Renal Medicine, Royal Prince Alfred Hospital, Sydney, NSW.
Adrian G Gillin, FRACP, PhD, Staff Specialist;
John S Horvath, MB BS, FRACP, Professor.

Reprints will not be available from the authors.
Correspondence: Dr A Cass, Menzies School of Health Research, PO Box 41096, Casuarina, NT 0811.
alancassATmenzies.edu.au






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Received 25 September 2018, accepted 25 September 2018

  • Alan Cass
  • Adrian G Gillin
  • John S Horvath


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