Review
Global complication rates of type 2 diabetes in Indigenous peoples: A comprehensive review

https://doi.org/10.1016/j.diabres.2008.07.017Get rights and content

Abstract

Introduction and objective

The world's Indigenous peoples are experiencing an unprecedented epidemic of type 2 diabetes [T2DM] but little has been published describing the complications burden. The objective of this paper was to conduct a systematic review of T2DM complications in Indigenous populations worldwide.

Methods

A literature review was conducted using PubMed and EMBASE to examine available complications data. Country, Indigenous population, authors, publication year, total sample size, Indigenous sample size, age, methodology, and prevalence of nephropathy, end-stage renal disease, retinopathy, neuropathy, lower extremity amputations, cardiovascular disease, hospitalizations and mortality due to diabetes were recorded.

Results

One-hundred and eleven studies were selected. Results revealed a disproportionate burden of disease complications among all Indigenous peoples regardless of their geographic location. Complication rates were seen to vary widely across Indigenous groups.

Discussion

Gaps were found in the published literature on complications among Indigenous populations, especially those living in underdeveloped countries. These gaps may be in part due to the challenges caused by varying operational practices, research methodologies, and definitions of the term Indigenous, making documentation of rates among these peoples problematic. Comprehensive surveillance applying standardized definitions and methodologies is needed to design targeted prevention and disease management strategies for Indigenous peoples with T2DM.

Introduction

A distinctive characteristic of the epidemiology of type 2 diabetes is the wide geographic and ethno-cultural variation in prevalence [1]. Incidence rates of type 2 diabetes have been on the rise worldwide in the last 30 years and, based on limited data, it seems to disproportionately affect some racial and cultural groups [2], [3], [4]. In particular, prevalence rates of the disease have reached epidemic proportions in Indigenous peoples. This is reflected, for example, in the Canadian First Nations peoples, where the crude prevalence of diabetes ranges from 8 to 13% [2] with some communities reaching as high as 25% [5], [6], which is a three- to five-fold increase compared to the general Canadian population [2].

Worldwide, the population of Indigenous peoples has been estimated at 300 million individuals, representing approximately 5000 different cultures from more than 70 different countries [7]. Despite this rich variation in location, language, history and culture, increased rates of type 2 diabetes in comparison to the non-Indigenous general population seem to be a shared phenomenon. This can be seen in the United States, where type 2 diabetes is a major cause of morbidity and mortality, with the highest rates of the disease seen in Native American communities [8], [9]. A recent global review of type 2 diabetes and impaired glucose tolerance [IGT] noted that despite a large variance in the prevalence of type 2 diabetes and IGT among Indigenous populations worldwide, the majority demonstrated higher rates of type 2 diabetes compared to their non-Indigenous counterparts [10]. The highest prevalence was found in the southern American Indian tribes at 40%, while Colombian Amerindians had the lowest at 0% [10].

Genetic susceptibility [11], [12] and rapid lifestyle changes over the past two or three generations, highlighted by a shift away from traditional lifestyles towards more sedentary living and Western diets [13], have left Indigenous peoples with a heightened risk for diabetes and premature mortality and morbidity. Factors that contribute to the suboptimal quality of diabetes care found in most Indigenous communities include geographical isolation and remoteness, limited healthcare staff and high staff turnover [14]. In addition, social factors such as inferior health care and social service infrastructure, inadequate environmental and social support for physical activity, limited availability of healthy foods, overpriced fresh foods and high rates of poverty also impact an individual's capacity for self-care [15], [16]. Furthermore, educational disadvantage, high unemployment rates and poor understanding of health and nutrition [13] all contribute to the increased risk of diabetes in Indigenous peoples. Some Indigenous groups face other health and social problems [e.g., addiction and substance abuse, fetal alcohol syndrome, unemployment, unsafe water supply, domestic violence] that may compete for the attention of health care professionals, policy makers and funding. The marginalization of Indigenous peoples, particularly in terms of access to specialized medical and allied health care, is a serious problem [2], [15], [17], [18].

Different understandings of the etiology of health and illness between Indigenous communities and biomedical practitioners may also influence care. While traditional biomedical explanatory models center the disease within the individual [19], often Indigenous people emphasize the collective social experience shared by the individual, the family, and the past and future community [5]. These lifestyle, environmental and cultural differences present difficulties in providing health care to Indigenous peoples that may compound the high rates of diabetes seen in these populations.

As with diabetes, the prevalence rates of diabetes-related complication appear to be elevated in Indigenous communities. Data from Aboriginal peoples in Canada show higher diabetic retinopathy rates [20] and while cardiovascular disease [CVD] has been declining in the general Canadian population, data seem to suggest increasing rates among Aboriginal peoples [21]. Currently, no global review of diabetes-related complications rates in Indigenous peoples exists. The objective of this review was to determine the prevalence rates of diabetes-related complications in the Indigenous populations of the world.

The lack of a standardized operational definition of the term Indigenous and terminology with which to describe Indigenous peoples may hinder research with Indigenous populations, as well as prove to be a barrier to identifying relevant literature when conducting reviews. Definitions of Indigenous range from the biological perspective of the United States Dawes Act [also known as the General Allotment Act] of 1887, which necessitated a minimum one-quarter blood requirement for Indigenous identification [22], to the United Nations definition, which transcends territoriality and relies on ethnic and cultural identity as well as political power [23]:

“Indigenous communities, Peoples and nations are those which, having a historical continuity with pre-invasion and pre-colonial societies that developed on their territories, consider themselves distinct from other sectors of the societies now prevailing in those territories, or parts of them. They form at present non-dominant sectors of society and are determined to preserve, develop, and transmit to future generations their ancestral territories, and their ethnic identity, as the basis of their continued existence as Peoples, in accordance with their own cultural patterns, social institutions, and legal systems.” [23]

The usual application of the term Indigenous is reserved for peoples who inhabited a geographical region before the arrival of colonizers [24]. A related, but separate, definition relies on a linguistic identity that differs from that of the dominant society [5]. These definitions rely on a shared experience that differs from that of others in the dominant group; however, the relationship between Indigenous peoples, their land and culture must also be acknowledged [25], as most Indigenous peoples view the world through their integral relationship with the natural world.

Section snippets

Search strategy

Two separate searches were carried out in the PubMed and EMBASE databases to identify English language articles published between 1990 and 2008 on the subject of type 2 diabetes complications in Indigenous populations. In PubMed, the combination of text words and MeSH [Medical Subject Headings] terms used included: ‘Asian continental ancestry group, African continental ancestry group, Oceanic ancestry group, American Native continental ancestry group, European continental ancestry group,

Study characteristics

The searches in PubMed and EMBASE yielded 1393 published papers. Of these, 111 [7.97%] were selected that met all the inclusion criteria. These studies involved 25 Indigenous groups from 5 countries. Individual sample sizes ranged from 10 [26] to 28,318 [27], with seven studies not reporting their sample size [28], [29], [30], [31], [32], [33], [34]. Participant ages ranged from 5 to 98 years, with the majority of studies involving people aged 20 years and older. Of the 111 included papers, 50

Discussion

There is a paucity of reliable data on diabetes-related complications amongst Indigenous peoples worldwide. The current review found published data from only five countries, namely: (1) the United States; (2) Canada; (3) New Zealand; (4) Australia; and (5) the Commonwealth of the Northern Mariana Islands. No studies that met the listed inclusion criteria were found on Indigenous peoples of developing countries, such as India. The scarcity of data reported for Indigenous peoples in Micronesia,

Conflict of interest

The authors declare that they have no conflict of interest.

Acknowledgements

Portions of this review were presented by SBH in June 2006 at the American Diabetes Association Annual Scientific Sessions in Washington DC, and in December 2006 at the 19th World Diabetes Conference in Cape Town, South Africa.

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