The impact of urbanisation on the cardiometabolic health of Indigenous Brazilian peoples: a systematic review and meta-analysis, and data from the Brazilian Health registry

Summary

Background

Indigenous Brazilian peoples have faced an unparalleled increase in the rate of cardiovascular diseases following rapid nutritional transition to more urban diets. We aimed to conduct a systematic review and meta-analysis to evaluate the association between urbanisation (including data from Amazon rainforest deforestation) and cardiometabolic risk factors and outcomes.

Methods

In this systematic review and meta-analysis, we searched Pubmed, Embase, Web of Science, and Scopus for articles published in any language between the year 1950 and March 10, 2022. Studies conducted in Indigenous Brazilian adults that evaluated metabolic health were included. Data for deforestation was obtained by the Amazon Deforestation Monitoring Project. Cardiovascular mortality was obtained from the Brazilian Health registry. Two independent reviewers evaluated studies for risk of bias, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses recommendations. The main outcomes assessed were the prevalence of obesity and related cardiometabolic risk factors among Indigenous Brazilian peoples and its association with urbanisation. Summary data were extracted from published reports for the meta-analyses. We calculated pooled estimates of the prevalence of each cardiometabolic outcome by using a random-effects model (DerSimonian–Laird method). This study is registered with the International Prospective Register of Systematic Reviews, CRD42021285480.

Findings

46 studies were identified, including a total of 20 574 adults from at least 33 Indigenous Brazilian ethnicities. Meta-analyses of the prevalence of obesity showed that there were higher rates of obesity (midwest region: 23% [95% CI 17–29]; and south region 23% [13–34]) and hypertension (south region: 30% [10–50]) in Indigenous peoples living in urban regions of Brazil, while the lowest rates of obesity (11% [95% CI 8–15]) and hypertension (1% [1–2]) were observed in those in the less urbanised (north) regions of Brazil. The prevalence of obesity was 3·5 times higher in participants living in urbanised Indigenous territories (28%) than in those living in lands with >80% native Amazon rainforest (8%). In meta-analyses that evaluated blood pressure level, there was no incremental change in blood pressure with ageing in Indigenous peoples who lived according to traditional lifestyle, in contrast to those living in urbanised regions. For Indigenous men with traditional lifestyles, systolic blood pressure changed from 109·8 mm Hg to 104·4 mm Hg between the youngest (<30 years) and the oldest (>60 years) age groups, and diastolic blood pressure changed from 69·8 mm Hg to 66·1 mm Hg. For Indigenous women with traditional lifestyles, systolic blood pressure was 100·0 mm Hg for the youngest age group with no changes for older age groups, and diastolic blood pressure was 62 mm Hg for the youngest age group with no changes for older age groups. For Indigenous men with urbanised lifestyles, systolic blood pressure changed from 117·3 mm Hg to 124·9 mm Hg between the youngest and the oldest age groups, and diastolic blood pressure changed from 72·7 mm Hg to 76·4 mm Hg. For Indigenous women with urbanised lifestyles, systolic blood pressure changed from 110·0 mm Hg to 116·0 mm Hg between the youngest and the oldest age groups, and diastolic blood pressure changed from 68·3 mm Hg to 74·0 mm Hg. For the years 1997 and 2019, the cardiovascular mortality rate in individuals living in the southeast region (the most urbanised) was 2·5 times greater than that observed in the north. Conversely, the incremental rise in cardiovascular mortality in the past two decades among Indigenous Brazilians living in the north or northeast (2·7 times increase) stands in stark contrast to the stable rates in those living in already urbanised regions.

Interpretation

The macrosocial changes of Indigenous peoples’ traditional ways of living consequent to urbanisation are associated with an increased prevalence of adverse cardiometabolic outcomes. These data highlight the urgent need for environmental policies to ensure the conservation of the natural ecosystem within Indigenous territories, as well as the development of socio-health policies to improve the cardiovascular health of Indigenous Brazilians peoples living in urban areas.

Funding

None.

Introduction

Previous studies have estimated that 8 million Indigenous individuals, representing over 1000 ethnicities, live in the territory currently corresponding to Brazil.¹ After the Portuguese conquest of Brazil in the year 1500, there was a large demographic collapse of native populations (corresponding to a reduction of approximately 90%), mainly due to foreign bacterial and viral diseases introduced by Europeans, which culminated in the extinction of coastal communities by the end of the 18th century and delimiting the Indigenous territory predominately to the Amazon region. The process of colonisation and Indigenous cultural oppression in Brazil occurred among forced African immigration (occurring between the 15th century and the 19th century) and subsequent European intentional overseas migration. These diverse ethnic populations have led to the contemporary multiethnic, highly-admixed Brazilian population that carries elements of native Indigenous culture and genetic heritage nationwide.1, 2, 3

In a Brazilian census from 2010, 896 000 individuals self-identified as Indigenous, comprising 305 ethnicities with 274 diverse languages, most (63·8%) of whom live in rural areas or Indigenous territories within the Legal Amazon region.³ Despite the important cultural legacy of native Indigenous people to modern Brazilian society, Indigenous peoples face an unprecedented public health crisis. The macrosocial changes imposed by western colonisation and urbanisation have disrupted the Indigenous traditional lifestyle and health systems, changing their relationship with the land and establishing a social-health structure that marginalises Indigenous people and discriminates against them.⁴ As a result, Indigenous Brazilian people have higher rates of mortality and morbidity indicators than non-Indigenous people.⁴

With respect to cardiovascular health, the process of urbanisation has been associated with accelerated weight gain, as well as a higher incidence of adverse cardiometabolic risk factors and outcomes in many Indigenous Brazilian ethnicities. While still enduring high rates of infant mortality due to preventable parasitic and infectious diseases, as well as chronic undernutrition,5, 6 several Brazilian Indigenous communities have faced an unparalleled increase in chronic non-communicable diseases following recent rapid nutritional transition.7, 8, 9 The prevalence of obesity and cardiometabolic diseases among Brazilian Indigenous populations, and its association with the degree of urbanisation and deforestation within Indigenous territories, is heterogeneous and largely understudied. We therefore aimed to conduct a systematic review and meta-analysis to evaluate the association between urbanisation and cardiometabolic risk factors and outcomes, including data from Amazon rainforest deforestation and Indigenous cardiovascular mortality.