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End stage renal disease in Aborigines in New South Wales: a very different picture to the Top End | par 0 |
| Alan Cass* MBBS FRACP, Adrian Gillin# FRACP PhD, Professor John Horvath# MBBS FRACP. | par 1 |
| *Menzies School of Health Research, Darwin, Northern Territory, Australia. | par 2 |
| #Department of Renal Medicine, Royal Prince Alfred Hospital, Camperdown, NSW, Australia. | par 3 |
Accepted for publication 19.7.99, electronically published 21.7.99 without editing.
This is the first revised version of this paper. Revisions are shown in blue text. ABSTRACT | par 4 |
| OBJECTIVES: To compare the incidence of end-stage renal disease (ESRD) among Aborigines in New South Wales (NSW) with the national incidence among Aborigines. To compare the patterns of ESRD: aetiology, patient demographics, and outcomes of treatment including survival after transplantation, among Aborigines and non-Aborigines in NSW, and with Northern Territory (NT) Aborigines. | par 5 |
| DESIGN: Secondary data review. | par 6 |
| METHODS USED: Information was obtained from unpublished and published Australia and New Zealand Dialysis and Transplant Registry (ANZDATA) Registry Reports (12, 18-21). | par 7 |
| MAIN OUTCOME MEASURES: Average annual incidence of ESRD (persons per million), patient status at 31/03/98 by type of renal replacement therapy or death, patient and graft survival 1 and 5 years post transplant. | par 7a |
| RESULTS: Each year in NSW 5-17 new Aboriginal patients were treated for ESRD. There was no increase in the average annual incidence of ESRD among NSW Aborigines (118 per million in 1988-89 and 111 per million in 1996-97), despite a significant increase in national incidence (156 per million in 1988-89 and 299 per million in 1996-97). The increase in incidence was even more rapid in the NT (255 per million in 1988-89 and 800 per million in 1996-97). Diabetes, glomerulonephritis and hypertension were the prominent primary causes of ESRD among NSW Aborigines. ESRD was attributed to diabetes in 32% Aboriginal patients compared to 13% non-Aboriginal patients (p<0.001). Aboriginal patients were younger: mean age 43.7 compared to 54.9 and more likely to be female. This pattern mirrors the data from the NT. The outcome of ESRD treatment is not significantly different between Aborigines and non-Aborigines in NSW. This contrasts with significantly worse survival with all forms of treatment for NT Aborigines. | par 8 |
| CONCLUSION: There is a different pattern of incidence of ESRD and of outcomes with treatment among NSW Aborigines, compared to Northern Territory Aborigines. The key unanswered question is whether this difference is real. It is possible that the lower incidence reflects less profound socioeconomic disadvantage and readier access to effective primary and specialist care. However a similar epidemic to that identified in the NT may be being masked by poor ascertainment of the extent of disease. | par 9 |
BACKGROUND | par 10 |
| Aboriginal communities are at the bottom of the scale of health and well-being in Australia. There is a consistent picture of excess mortality at all ages and excess morbidity due to malnutrition, infectious diseases and chronic illness. Community studies in the Northern Territory (NT) have demonstrated a marked increase in the prevalence of renal disease associated with diabetes, hypertension and glomerulonephritis. 1 High rates of albuminuria have been shown in the Victorian Aboriginal community. 2 Documentation of chronic renal disease in New South Wales (NSW) is poor. | par 11 |
| Aboriginal people experience high morbidity and mortality due to end-stage renal disease (ESRD). The average annual incidence of ESRD for Aborigines in the NT in 1988-1993 was 17.4 times that of non-Aborigines. 3 Such disparities are made more apparent by age adjustment. 4 The number of dialysis treatments in the NT is doubling every two years. 5 The 30 June 1996 estimate of the Indigenous population (386 049), represented 2.1% of the total Australian population. 6 Aborigines however, constitute 5% of the Australian members of the Australian and New Zealand Dialysis and Transplant Registry. 7 This is more than double their proportion in the community. | par 12 |
| The estimated resident Indigenous population of NSW, at 30 June 1996, was | par 13 |
| 109 925. This represented 28.5% of the Australian Indigenous population and 1.8% of the total NSW population. 6 The age-standardised death rates for Aborigines and Torres Strait Islanders in NSW were close to that of the non-Aboriginal community: 809 per 100,000 men and 556 per 100,000 women for the years 1985-92. This represented a Standardised Mortality Ratio (SMR) of 1.2 for men and women. 8 This figure may conceal a significant urban/rural differential in mortality. Data for country areas of NSW have shown a four times higher mortality amongst Aborigines when compared with non-Aborigines. The greatest difference was in the age range 25-44 years.9 | par 14 |
AIMS | par 15 |
| The aims of this study were: |
| To document the number of new Aboriginal patients in NSW with ESRD and to compare recent trends in incidence with national and NT data regarding incidence of ESRD in Aborigines. | par 17 |
| To compare the patterns of aetiology of ESRD of NSW Aborigines and non-Aborigines. | par 18 |
| To compare the demographic characteristics of NSW Aborigines and non-Aborigines at the time of being entered onto the ANZDATA registry. | par 19 |
| To compare the outcomes for NSW Aborigines and non-Aborigines who have come onto the registry during the period 1987 to 1998. | par 20 |
| To compare patient and graft survival for NSW Aborigines and non-Aborigines who have received transplants during the period 1987 to 1998. | par 21 |
| To compare patterns of aetiology, demographic characteristics and outcomes for NSW Aborigines with recently published data regarding ESRD in Aborigines in the NT. | par 22 |
METHODS | par 23 |
| Information was obtained from two sources: published ANZDATA Reports (12 and 18-21) and unpublished data from ANZDATA. The Registry provided the numbers of patients who had commenced treatment between 1987 and 1998 in NSW and of transplants performed during the same period in NSW. The figures were broken down into Aboriginal and non-Aboriginal groups. All nephrology units in Australia and New Zealand that provide dialysis or transplant services, submit detailed six-monthly reports to the Registry. 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. | par 24 Comment |
| The following information was analysed: the number of Aboriginal patients entered into the Registry in NSW, the NT and across Australia; the average annual incidence of ESRD; primary renal disease by gender and Aboriginality; mean age and standard deviation of new patients by Aboriginality; Aboriginality and gender of new patients over 65 years of age at entry and of those less than 20 years of age at entry. Outcome data at 31 March 1998 were analysed by Aboriginality for people who had been entered into the Registry since 1 Jan 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 by Aboriginality were sub-categorised into cardiac, vascular, infection, social, malignancy and other. Data regarding transplants performed between 1 Jan 1987 and 31 March 1998 were analysed by Aboriginality and age, patient survival and graft survival. | par 25 Comment |
| 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 2-year period, as there is marked variability in the number of new patients per year, and small numbers in absolute terms. | par 26 Comment |
| Statistical analysis of demographic and outcome data was performed using STATA 5.0 (College Station, Texas, USA). A t test of means and chi-square 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 appropriately graphed. | par 27 |
RESULTS | par 28 |
| Each year in NSW, 5 – 17 new Aboriginal patients are treated for ESRD (Table 1). The average annual incidence of ESRD among Aborigines in NSW for 1988-89 was 118 per million. This remained substantially unchanged at 111 per million in 1996-97. During the same period there was a significant increase in average annual incidence of ESRD in Aborigines across Australia, rising from 156 per million in 1988-89 to 299 per million in 1996-97. In the Northern Territory, the rise in incidence was more marked; from 255 per million in 1988-89 to 800 per million in 1996-97. The crude incidence for non-Aborigines in NSW was 78 per million for 1993-97, a slight rise from the 1980s being due to increased acceptance for dialysis of patients over the age of 65. The epidemic of renal failure among Australian Aborigines in the Northern Territory is not mirrored in NSW. | par 29 Comment |
| There is a high prevalence of diabetes, glomerulonephritis and hypertension as the primary renal diseases (PRD) among Aborigines with ESRD (Table 2). Diabetes is listed as the PRD in 32% of Aborigines compared to 13% of non-Aborigines (p<0.001). There is no significant difference in the proportion of ESRD attributed to glomerulonephritis (p=0.58) or hypertension (p=0.83). Polycystic disease and reflux nephropathy are attributed as the PRD in only 1% of Aborigines, significantly different from the non-Aboriginal group: polycystic disease p=0.007 and reflux nephropathy p=0.04. Analgesic nephropathy affects a significantly greater proportion of the non-Aboriginal population: 15% compared to 6% (p=0.01), mainly among females; 28% in non-Aboriginal females compared to 10% in Aboriginal females. No definite diagnosis was recorded for 11% of Aborigines compared to 5% of non-Aborigines (p=0.004). | par 30 Comment |
| The demographic patterns of the patient groups at entry to the ESRD program and the general outcomes as at 31 March 1998 are presented in Table 3. There are significantly more females than males amongst Aborigines, the reverse pattern to the non-Aborigines (p=0.03). The Aboriginal population is younger at entry to the program and there are significantly fewer people over the age of 65 (p<0.001). Outcome, or patient status at 31/3/98, is not significantly different between the groups (p=0.59). There is no significant difference in the proportion of people who have died, have functioning transplants or are receiving different forms of dialysis. However, no attempt at age or sex standardisation has been made in this analysis. | par 31 Comment |
| The differences in causes of death approach statistical significance (p=0.07). | par 32 |
| A significantly larger proportion of Aborigines died from cardiovascular diseases, 71.8% compared to 51.8% (p=0.01). There is no significant difference in the proportion who died from infection (p=0.82) or malignancy (p=0.36). A significantly smaller proportion died due to social reasons, 2.5% compared to 15.2% (p=0.02). This category includes patients who refused further treatment, who committed suicide, who ceased therapy for any other reason or who died from an accident. | par 33 |
| Aboriginal patients receiving transplants during the study period were younger (Figure 2) but experienced lower patient survival and graft survival rates (Figures 3 and 4). Patient survival after transplantation at 1 year was 91.3% for Aborigines (95% confidence interval (CI) 81.9 – 100%) versus 92.7% for non-Aborigines (95% CI 91.5 – 93.9%). Patient survival at 5 years was 73.8% for Aborigines (95% CI 56.2 – 91.4%) versus 82.5% for non-Aborigines (95% CI 80.5 – 84.5%). The log rank test, however, indicated no significant statistical difference between the groups (p=0.11), and thus no apparent difference in patient survival. Graft survival at 1 year was 76.8% (95% CI 62.7 – 90.9%) versus 83.1% (95% CI 81.3 – 84.9%), and at 5 years 65.0% (95% CI 45.8 – 84.2%) versus 70.7% (95% CI 68.3 – 73.1%). The log rank test again indicated no significant difference in graft survival between the groups (p=0.36). | par 34 Comment |
DISCUSSION | par 35 |
| Diabetes, glomerulonephritis and hypertension are the prominent primary causes of ESRD among NSW Aborigines. Diabetes is attributed as the primary renal disease for 32% of patients, more than double the proportion (13%) for non-Aboriginal patients. The rise in renal failure attributed to diabetes follows a similar pattern to that noted in Aborigines across Australia. The higher proportion of Aboriginal patients without a definite diagnosis is consistent with a lower renal biopsy rate. This may relate to late referral and lack of access to renal specialist services. It appears that there is no significant difference in the pattern of primary causes of renal disease between Aboriginal populations in different states. | par 36 |
| The Aboriginal patient with ESRD is on average ten years younger, more likely to be female, and more likely to have diabetes and to die from cardiovascular disease. These features are mirrored in the NT data. 4 However, there is no significant difference in outcome between Aboriginal and non-Aboriginal patients in NSW who have been entered into the registry since January 1987. The proportion of people who have died, have functioning transplants, or are on various forms of dialysis are not significantly different. This contrasts with significantly worse survival with all forms of treatment in Aboriginal patients in the NT. 4 The persistently high rate of withdrawal of NT Aboriginal people from ESRD treatment, approximately 25%, is not mirrored in NSW. | par 37 |
| 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. Therapeutic programs have typically removed people from their cultural and social support networks by requiring patients to leave their land, families and communities.10 Aborigines in NSW reside predominantly in cities and rural towns. Unlike in the Northern Territory, South Australia and Western Australia, there are few remote, non-urbanised communities. In NSW, specialist renal services are increasingly being provided where Aborigines 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%). 11 CAPD training is now occurring in some larger rural centres. Haemodialysis facilities are provided in Bourke and Brewarrina. These initiatives, which significantly reduce the dislocation of the patients from their community and remove impediments to the delivery of appropriate ESRD services, may facilitate improved survival. | par 38 Comment |
| There is a tendency towards lower patient survival and graft survival post-transplant among NSW Aborigines. The larger 95% confidence intervals in the Aboriginal group are a consequence of fewer transplants being performed: 36 among Aboriginal patients compared to 1755 among non-Aboriginal patients. The small number of transplants among Aboriginal patients does not provide sufficient power to detect a significant difference between the groups. Data from the NT, however, show significantly worse graft and patient survival among Aborigines at 1 and 5 years. 4 A similar tendency towards lower survival is evident in the NSW data despite the graft recipients being younger, and therefore more likely to demonstrate better patient and graft survival. | par 39 |
| These data show no evidence of an epidemic of renal failure among Aborigines in NSW despite the fact that the incidence remains higher than among the Caucasian population. The pattern of rapidly increasing incidence of ESRD among Aborigines across Australia, especially in the NT, is not repeated in NSW. Spencer et al argue that the increase in the NT is real, not due to ageing of the Aboriginal population nor due to improved ascertainment. 4 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 by Van Buynder1 and Hoy4 show a prevalence of significant proteinuria in marked excess of the prevalence of diabetes or impaired glucose tolerance. Hoy showed that the average annual incidence in NT Aborigines for 1988-93, of ESRD not attributable to diabetes was 350 per million per year.3 Lower incidence of ESRD in NSW Aborigines may reflect less profound socioeconomic disadvantage and readier access to effective primary and specialist care . There may however, be poor ascertainment, particularly in rural areas of NSW. Further study is indicated to analyse this question. | par 40 Comment Comment |
ACKNOWLEDGEMENTS | par 41 |
| 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. | par 42 |
| Dr Alan Cass is the recipient of a postgraduate research scholarship from the New Children’s Hospital, Sydney and support from the Australian Kidney Foundation. | par 43 |
We
thank Dr Wendy Hoy who critically reviewed the manuscript and Dr Zhiqiang Wang
who provided statistical advice.
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REFERENCES | par 52 |
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