Urbanization And Kidney Dysfunction in Brazilian Indigenous People: A Burden For The Youth

SUMMARY

OBJECTIVE: The aim of this study was to investigate whether the degree of urbanization influences the prevalence of chronic kidney disease in Brazilian indigenous people. 

METHODS: This is a cross-sectional study conducted between 2016 and 2017 in northeastern Brazil and includes individuals aged between 30 and 70 years from two specific indigenous groups who volunteered to participate in the study: the Fulni-ô people (lowest degree of urbanization) and the Truká group (greater degree of urbanization). Cultural and geographical parameters were used to characterize and measure the magnitude of urbanization. We excluded individuals with known cardiovascular disease or renal failure who required hemodialysis. Chronic kidney disease was defined as a single measurement of an estimated glomerular filtration rate <60 mL/min/1.73 m2 using the Chronic Kidney Disease Epidemiology Collaboration creatinine equation. 

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RESULTS: A total of 184 indigenous people from the Fulni-ô group and 96 from the Truká group with a median age of 46 years (interquartile range: 15.2) were included. We found a chronic kidney disease rate of 4.3% in the total indigenous population, generally affecting an older population: 41.7% over 60 years old (p<0.001). The Truká people had a chronic kidney disease prevalence of 6.2%, with no differences in kidney dysfunction across age groups. The Fulni-ô participants had a chronic kidney disease prevalence of 3.3%, with a higher proportion of kidney dysfunction in older participants (of the six Fulni-ô indigenous people with chronic kidney disease, five were older). CONCLUSION: Our results suggest that a higher degree of urbanization seems to negatively influence the prevalence of chronic kidney disease in Brazilian indigenous people. 

KEYWORDS: Chronic kidney disease. Urbanization. Indigenous peoples

INTRODUCTION 

Chronic kidney disease (CKD) is one of the most important public health concerns of the century, and it is known to be associated with high rates of mortality and social costs1. It is characterized by severe, irreversible kidney damage with a reduced glomerular filtration rate of <60 mL/min/1.73 m2 or a urinary albumin-to-creatinine ratio of ³30 mg/g2. Previous studies have shown an increasing prevalence of CKD among indigenous people. When comparing outcomes with the general population, indigenous communities present higher mortality rates3 .

Similar to other colonized indigenous populations3, Brazilian indigenous people have undergone an accelerated process of nutritional and epidemiological transition characterized by reduced physical activity and the incorporation of new cultural habits. These factors have promoted the emergence of chronic diseases, such as CKD, and risk factors, such as obesity, hypertension, hyperglycemia, dyslipidemia, and diabetes, among indigenous people4-6. However, the literature describing the prevalence and determinants of CKD in Brazilian indigenous people is still scarce.

The Project of Atherosclerosis among Indigenous Populations (PAI) is a population-based study conducted in the Northeast Region of Brazil. The aim of this project was to assess cardiovascular health in indigenous groups with different degrees of urbanization. Between 2016 and 2017, the PAI study recruited 999 individuals, with no known previous cardiovascular event, who were inhabitants of the following three communities in the São Francisco River basin: two indigenous tribes (the less urbanized Fulni-ô and the more urbanized Truká people) and an urbanized non-indigenous control group from the same area4.

For this report, we exclusively assessed indigenous participants in the PAI study with available estimated glomerular filtration rate (eGFR) and clinical data to describe the prevalence of CKD and associated risk factors in both Brazilian indigenous communities living in different degrees of urbanization. Our hypothesis was that the group with a high degree of urbanization would have the highest prevalence of CKD.

METHODS 

The PAI study was approved by the National Research Ethics Council (CONEP number 1.488.268), the National Indigenous Foundation (Fundação Nacional do Índio [FUNAI]; process number 08620.028965/2015-66), and the indigenous leaders of both participating groups. All participants provided written informed consent before enrollment in the study

Study design and recruiting 

The PAI study has been described previously. Briefly, it is a descriptive, cross-sectional study composed of two specific indigenous groups from the Sao Francisco Valley in the northeast of Brazil (Figure 1). These groups were assessed between 2016 and 2017 and then stratified by degree of urbanization: the Fulni-ô people with a low level of urbanization and the Truká group with a high level of urbanization. The classification of the degree of urbanization was based on the following group characteristics: geographical location, maintenance of traditional culture, proximity to and contact with cities, and influence of the city on the group’s dynamics7,8.

The PAI study included individuals aged between 30 and 70 years who voluntarily agreed to participate in the study. Those with clinically manifested heart failure, a history of coronary or cerebrovascular vascular diseases requiring hospitalization, renal failure on dialysis, or a history of surgery for peripheral arterial disease or heart disease were excluded. 

The current analysis was carried out as an ancillary study of the PAI study, assessing participants with complete data on kidney function. In total, we analyzed 280 individuals: 184 (65.7%) from the Fulni-ô group and 96 (34.3%) from the Truká group.

Sociodemographic and anthropometric parameters 

We registered sex as a binary variable (male/female). Age was computed as a continuous variable in years, as well as categorized within four proportional groups (30–39, 40–49, 50–59, and 60–70 years). Individuals were classified according to body mass index as underweight (<18.5), normal (≥18.5 and <25), overweight (≥25 and <30), and obese (≥30). Obesity was subdivided into categories: class 1 (30 to < 35), class 2 (35 to <40), and class 3 “severe” obesity (>40)9 . 

Clinical parameters and laboratory testing 

Hypertension was defined as systolic blood pressure ≥140 mmHg, diastolic blood pressure ≥90 mmHg, or taking hypertension medications10. Diabetes was diagnosed when HbA1c was ³6.5% or using diabetes medications11. Dyslipidemia was established if the participant was using hypolipidemic medication or if at least one of the following criteria was met: reduced high-density lipoprotein cholesterol, a level <40 mg/dL in men or 50 mg/dL in women; hypertriglyceridemia, a triglyceride level >150 mg/dL; and hypercholesterolemia, low-density lipoprotein cholesterol>160 mg/dL12. 

The estimated glomerular filtration rate was calculated using the CKD Epidemiology Collaboration (CKD-EPI) creatinine equation without correction for race. According to the 2012 KDIGO criteria2, we classified the participants into three categories: normal/high (G1) (eGFR: ≥90 mL/min/1.73 m2 ), mildly decreased excretory renal function (G2) (eGFR: 60–89 mL/min/1.73 m2 ), and substantially reduced (G3) (eGFR: <60 mL/min/1.73 m2 ). We defined CKD as a single measurement of eGFR <60 mL/min/1.73 m2. 

Statistical analysis

The following statistical tests were used: the Shapiro-Wilk test for data distribution evaluation and analysis of variance to compare age distribution according to different grades of eGFR (and Tukey’s post hoc test, when necessary). In this analysis, confidence intervals of 95% and a significance level of 5% were used. Continuous quantitative variables were presented through central tendency and dispersion (mean standard deviation) and qualitative variables through frequencies (absolute and relative). Significant associations were considered when p<0.05. 

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