risk for end-stage renal disease (ESRD) than the Canadian population in general. ... We requested special computer runs and obtained cus- tom tabulations of ...
Excessive Burden of End-State Renal Disease among Canadian Indians: A National Survey T. KUE YOUNG, MD, MSC, JOSEPH M.
PHD, JOHN K. MCKENZIE, MD, AUDREY HAWKINS, BN, JOHN O'NEIL, PHD
KAUFERT, AND
Abstract: Analysis of data from the Canadian National Renal Failure Register indicates that Canadian Natives are at much higher risk for end-stage renal disease (ESRD) than the Canadian population in general. Using two population estimates for the total Native population, the age-standardized incidence rate of newly registered ESRD cases between 1981 and 1986 among Natives was at least 2.5 times (and may be as high as four times) the national rate. Natives
particularly at higher risk for ESRD to diabetes, glomerulonephritis, and pyelonephritis, whereas for the other causes the risk was no different from that of other Canadians. As technologically sophisticated treatment facilities are only available in major urban centers, Native ESRD patients and their families living in remote areas of Canada are faced with major psychosocial disruptions of relocation. (Am J Public Health 1989; 79:756-758.)
Introduction Ethnic differences in the incidence of end-stage renal disease (ESRD) have been observed in some populations. In the United States, Blacks and Hispanics generally have higher rates than Whites.`13 Recent reports from the American Southwest also show that the rate among some Indian tribes, particularly the Zuni, exceed those of Whites by several- fold.4'5 It is not clear if such a phenomenon is also observed in other Amerindian groups across the continent. This paper reports on the first phase of a multidisciplinary study examining the epidemiological, clinical, and sociocultural dimensions of ESRD among Canadian Indians.
the period 1981-86, comparing Native and non-Native patients. In the designation of "racial origin," the National Register distinguishes between Caucasian, Oriental, Black, Native, and other groups. Although the term "racial origin" connotes genetic differences, ascription of individuals to the above categories is more generally made on the basis of "ethnicity," a term which combines genetic (and usually physiognomous) characteristics with socio-cultural, environmental, political, and administrative attributes. The criteria for determining these attributes are subject to considerable interpretation and, at the present time, the National Register does not provide detailed criteria to the individual reporting renal units for establishing "ethnicity" or "racial origin." To investigate how people of Native ancestry were designated, we interviewed the clinicians responsible for data entry and reviewed the records of one provincial unit. In the central dialysis unit with the highest proportion of Native clients, review of the register and preliminary audits of patient records of all clients (N = 63) revealed that 28 percent were designated as Native and 72 percent non-Native. We searched for documentation of band number (which signifies legal membership in a government recognized Indian group), home community address, indication of need for translation services in a Native language, staff notations indicating self-ascription of Native identity, or staff notes indicating attribution of Native ancestry on the basis of physical characteristics or personal history. None of the patients listed in the registry as non-Native were found to have any information indicating Native ancestry. All but four of the patients categorized as Native by the registry had official Indian band numbers listed; among these four individuals, records and follow-up interviews with the nursing staff indicated that two had described their identity as Metis or non-status Indian and two were identified on the basis of language patterns, home address, and physical appearance as being of Native ancestry. In Canada, there are several categories of Native Peoples. These include Registered (Status or Treaty) Indians, non-status Indians, Metis, and Inuit (Eskimos). Metis are descendants of mixed Indian-White marriages during the early settlement of the Canadian West. They constitute a distinct cultural and political group in Canada today. According to the 1981 Census of Canada, Registered Indians constituted only 60 percent of all Native Peoples in the country. Since it is not clear as to the true denominator of the Native cases identified by the National Register, two different estimates ofthe Native population of Canada were used in the
Methods The Canadian National Renal Failure Register-jointly funded by the Department of National Health and Welfare, Statistics Canada, and the Kidney Foundation of Canadahas collected statistics on chronic renal failure patients since 1981. The register aggregates demographic and clinical data from 75 treatment centers in the nine Canadian provinces with specialized dialysis and transplant programs. It is population-based, voluntary and covers all active renal treatment centers in the nation.6 Data on all registered patients is updated yearly from medical record reviews in each center to reflect changes in treatment modalities and location, transplant experience and mortality. Patient proffles include age, sex, racial origin, birth date, course of treatment, method of treatment, transplant experience, donor type, cause of graft failure, and cause of death. There is no duplicate counting even as patients are transferred from one center to another. The coding categories and entry criteria are generally compatible with those developed and used internationally by the European Dialysis and Transplant Association.7 We requested special computer runs and obtained custom tabulations of all newly registered ESRD cases during Address reprint requests to T. Kue Young, MD, Associate Professor, Department of Community Health Sciences, University of Manitoba, 750 Bannatyne Avenue, Winnipeg, Manitoba, Canada R3E OW3. Drs. Young, Kaufert, and O'Neil are with the Northern Health Research Unit, Faculty of Medicine, University of Manitoba; Dr. McKenzie and Ms. Hawkins are with the Division of Nephrology, Department of Medicine, Health Sciences Center, Winnipeg. This paper, submitted to the Journal September 30, 1988, was revised and accepted for publication December 21, 1988. X 1989 American Journal of Public Health 0090-0036/89$1.50
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ESRD AMONG CANADIAN INDIANS
computation of rates. The Department of Indian and Northern Affairs (DINA) publishes annually the population by age, sex, and residence of all Registered Indians in Canada. The 1984 (representing the mid-point of the study period) Registered Indian population serves as the "A" estimate. This is a low estimate and assumes all Native cases in the register were exclusively Registered Indians. A second, higher estimate of the denominator assumes that the Native ESRD cases belong to all categories of Native Peoples. By dividing the "A" population estimate by 60 percent we obtained an estimate (the "B" estimate) of the total Native population in 1984. It is likely that the true denominator lies somewhere between the "A" and "B" estimates. As the age structure of the Native population differs substantially from the Canadian national population, the former being much younger, age standardization was performed using the Canadian population as standard. The mid-period population was obtained by averaging the 1981 and 1986 Census of Canada population by age-sex groups. In the comparison of total all-causes incidence rates, the direct method of age-standardization was used. In the comparison of cause-specific rates, standardized incidence ratios (SIR) were computed using the indirect method, due to the much smaller population within each age-sex class. Ninety-five percent confidence intervals were computed for all rates and ratios.8 Results
During the period 1981-86, there were a total of 8,432 newly registered cases of ESRD in Canada (5130M, 3302F), of whom 304 were categorized as Native (162M, 142F). Table 1 indicates that at all age-sex groups, the Native rate (23.1/ 100,000 using the "A" estimate and 13.9/100,000 with the "B" estimate), regardless of whether the "low" or "high" population estimate was used, was higher than the Canadian national rate. Age-standardization resulted in an even higher Native rate, which may be as high as four times and at least 2.5 times the national rate. The proportion of cases due to diabetes and glomerulonephritis is higher among Natives than all Canadians,
whereas the proportion due to renovascular disease and polycystic kidneys is lower (Table 2). In terms of the SIR by cause, Natives are at least at twice the risk as all Canadians for ESRD due to diabetes, glomerulonephritis, and pyelonephritis. Sixty-two percent of Native patients received hemodialysis as the initial treatment compared to 56 percent among all Canadians. The crude prevalence of ESRD at period end (December 31, 1986) was 22.3/100,000 for all Canadians, and 53.4 ("A" estimate) or 32.0 ("B" estimate) for Natives. The cumulative mortality rate for all newly registered patients during this period was comparable for the two groups: 33.1 percent for all Canadians and 31.9 percent for Natives.
Discussion This national survey confirms clinical observations and limited mortality and hospital utilization data that a higher burden of ESRD exists among the Native population of Canada. The extent and magnitude of ESRD in the Indian population of Canada has not been adequately assessed. However, several crude estimates based on death certificates and medical care insurance claims suggest that the risk of renal disease is higher among Indians than the general
population. A study of mortality among residents of Indian reserves aged 1-69 in seven provinces from 1977-82 showed that, while kidney diseases were not among the 10 highest ranking causes of death, Indian men had two times and Indian women four times the risk of dying from kidney diseases compared to Canadians nationally.9 According to claims submitted to the Manitoba Health Services Commission, the provincial health care insurance agency, the hospital separation rate for Manitoba Indians for all genitourinary diseases (ICD-9 codes 580-629) was 15.5/1000 per year, compared to 10.2/1000 for all Manitobans. For the rubrics "nephritis, nephrotic syndrome and nephrosis" (codes 580-589) the Indian rate was 1.4/1000 and the provincial rate was 0.4/1000. The agestandardized ratio for all genitourinary diseases comparing Indian with the provincial total was 2.3.
TABLE 1-Incidence Rate of Newly Registered Chronic Renal Failure: Comparison of Canadians, 1981-86
Age-Sex Group Male (years) 0-4 5-14 15-24 25-44 45-64 65+ Subtotal Female (years) 0-4 5-14 15-24 25-44 45-64 65+ Subtotal Total (Crude)
Canadians
(A)
0.71 0.68 2.68 5.65 14.23 21.06 6.96
1.90 3.31 3.46 2.52 4.04 3.32 2.15
0.46, 1.45, 2.28, 1.82, 3.15, 2.31, 1.84,
0.38 0.71 2.05 3.35 8.80
1.87 4.41 2.76 4.02 6.34 5.26 3.03 2.50
2.11, 1.61, 2.89, 4.87, 3.51, 2.56, 2.23,
4.39 5.66
with all
Rate Ratio Native:Canada
All
10.15
Natives
95% Cl
(B)
95% Cl
7.94 7.62 5.29 3.48 5.20 4.76 2.51
1.14 1.99 2.08 1.51 2.43 1.99 1.29
0.28, 4.76 0.87, 4.57 1.37, 3.17 1.09, 2.09 1.89, 3.12 1.39, 2.85 1.10, 1.51
0.25,13.91
1.13 2.65 1.65 2.41 3.80 3.16 1.82 1.50
0.15, 8.35 1.27, 5.44 0.96, 2.82 1.74, 3.36 2.92, 4.95 2.11, 4.73 1.54, 2.15 1.34,1.68
9.07 4.71 5.60 8.24 7.89 3.59 2.80
NOTES: All rates are expressed as cases per 100,000 population/per year. (A), (B)-See text for definition of different Native Canadian populaton estimates.
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YOUNG, ET AL. TABLE 2-Etiology of ESRD in Canada, 1981-86: Native vs All Canadians
Cause
Glomerulonephritis Diabetes Mellitus Renovascular Disease Pyelonephritis Polycystic Kidneys Drug-induced Nephropathy Others Unknown
All Canadians
Natives
n = 8432
n = 304
24.5% 17.7 13.0 10.6
29.3% 25.7 3.3 11.8 2.6 0.3 14.5 12.5
7.2 1.8 14.4 10.9
SIR 4.1 5.3 1.2 3.8 1.5 0.8 3.3 5.3
(A) Estimate 95% Cl
SIR
3.3, 5.0 4.2, 6.6 0.6, 2.2 2.6, 5.3 0.7, 3.0 0.0,4.4 2.4,4.4 3.8, 7.2
3.2 0.7 2.3 0.9 0.5 2.0 3.2
2.4
(B) Estimate 95% Cl
1.9, 3.0 2.5, 4.0 0.3,1.3 1.6, 3.2 0.4, 1.8 0.0, 2.8 1.5, 2.7 2.3, 4.4
NOTE: (A), (B)-See text for definition of different Native Canadian population estimates. SIR = Standardized Incidence Ratios.
The precise causes for this phenomenon are not known but may have been due to the higher prevalence of diabetes mellitus'0"' known to be present in many Indian groups. Diabetes accounts proportionately for more ESRD cases among Natives than other Canadians. The incidence of impetigo-related post-streptococcal glomerulonephritis is also higher in Native communities, although it has yet to be established that such cases are more likely to proceed to ESRD. It is also interesting that, among the different sites of cancers, Indians are particularly at high risk for kidney cancers.12'13 It would therefore appear that, for a variety of environmental and genetic reasons, the kidneys of Canadian Natives are highly susceptible to pathologic derangements which may result in ESRD or malignant change. The lack of uniform and clearly defined criteria for racial origin in the National Register and its confusion with ethnic identity, however, impose some reservation on our conclusions. Many people designated as Native using nongenetic criteria are usually of mixed racial heritage which obviously complicates discussions of genetic predisposition to certain diseases. Furthermore, different renal reporting centers may have greater or lesser sensitivity to sociocultural or environmental criteria for determining Nativeness which may contribute to either over- or under-reporting errors. To assess variability in the designation of ethnicity, current criteria and validity of data on Native ancestry in each of the country's treatment centers need to be documented. The demonstration of an excess in the burden of ESRD among Canadian Natives has profound implications for health care delivery. In order to survive, patients must depend on technologically sophisticated and professionally controlled treatment provided in urban hospitals. Many Native communities in Canada are located in remote areas, and relocation of Native patients and their family members for medical treatment disrupts social support patterns and creates a host of psychosocial problems. Further epidemiological analyses will determine ethnic differences in the distribution of risk factors, types, and frequency of complications, survival experience, the impact
758
of urban migration and interaction with medical technology. Concurrently the cultural and socioeconomic basis for discontinuities between service providers' and Native clients' interpretation of treatment alternatives, risk factors, and quality of life will be examined. ACKNOWLEDGMENTS
The authors wish to acknowledge the assistance of Daniel Luca, Production Manager of the Canadian Renal Failure Register, Anita Rappaport of the Vital Statistics and Health Status Section, Statistics Canada, and Dr. J.R. Jeffery of the Health Sciences Center, Winnipeg. Funding for this project is provided by the Manitoba Health Research Council.
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