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

RESULTS 

A total of 280 indigenous participants were included: 184 (65.7%) from the Fulni-ô group and 96 (34.3%) from the Truká group, with a median age of 46 (interquartile range: 15.2) years in the entire cohort. According to the 2012 KDIGO criteria2, 59.9% of all participants had normal/high eGFR; 37.8% had mildly decreased excretory renal function (eGFR: 60–89 mL/min/1.73 m2 ); and 4.3% had substantially reduced eGFR (<60 mL/min/1.73 m2 ), which generally affected a higher age population (p<0.001) (Figure 2A).

Figure 2. Glomerular filtration rate stage (Chronic Kidney Disease Epidemiology Collaboration, without race correction) of the study population: (A) total population; (B) Fulni-ô; and (C) Truká.

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In a more advanced degree of urbanization, the Truká people had a CKD prevalence of 6.2%, with no differences in kidney dysfunction across age groups. On the contrary, the Fulni-ô participants had a CKD prevalence of 3.3%, with a higher proportion of kidney dysfunction in older participants (of the six Fulni-ô indigenous people with CKD, five were older), when compared to young people from the same ethnicity (Figures 2B and 2C). In the prevalence of CKD between the two indigenous groups, no statistically significant difference was found (p=0.068) (Table 1). The Truká people presented a younger population with mildly to moderately decreased kidney function, with a median age of 47.5 years, contrasting with the median age of 63.5 years in the G3 Fulni-ô subgroup (Figures 2B and 2C).  

The prevalence of hypertension and diabetes was 24.6 and 9.3%, respectively. Regarding the prevalence of hypertension, no association was found between the groups according to the eGFR. As for diabetes, the prevalence in the indigenous with an eGFR <60 mL/min/1.73 m2 was 25% (3/12) compared to 8.6% (23/268) in the group with an eGFR ≥60 mL/min/1.73 m2 (p=0.0453) (Table 1).

Notably, 95 (33.4%) individuals were classified as obese and 109 (38.9%) as overweight. No association was found between the prevalence of obesity in the groups according to estimated eGFR (p=0.327). However, among traditional risk factors for developing CKD, obesity was the only factor that showed a significant difference between the two indigenous groups, with a higher prevalence in the group with the highest degree of urbanization: 43.7% among the Truka (42/96) and 28.8% among the Fulni-ô (53/184) (p=0.0124) (Table 1).

DISCUSSION 

We identified a tendency of worse kidney function among the more urbanized Truka ethnicity when compared to the Fulni-ô people, suggesting that a more urbanized setting might be associated with worse kidney function. Additionally, our results also suggest that younger individuals are affected with intensity similar to the elderly among the indigenous populations with advanced urbanization levels.

The ELSA-Brazil cohort reported that 4.8% of the overall Brazilian population (n=14,636) had an eGFR below 60 mL/min/1.73 m2 , compared to 7.2% of the 153 self-declared indigenous participants1. Socioeconomic disadvantages do not seem to fully explain the higher prevalence of CKD among indigenous participants in the ELSA study, as the entire cohort had stable employment and a high level of education. In accordance with our results, the ELSA study findings might, at least in part, be explained by the fact that the indigenous participants have experienced acculturation in a highly urbanized setting.

In non-indigenous Brazilian adults, the prevalence of systemic arterial hypertension is 21.4%13. In our study population, the prevalence of systemic arterial hypertension was slightly higher. However, this prevalence is slightly lower than in other ethnic groups that have been studied previously. Other traditional risk factors related to CKD, such as diabetes mellitus and obesity, also showed considerable prevalence. 

In relation to diabetes mellitus, according to a recently conducted survey14, the prevalence in the study groups was similar to that found in the Brazilian population and associated with CKD. This result may be closely linked to the high prevalence of obesity in this population, with an alarming prevalence of 33.4%. This number is higher than that found in a population-based survey conducted in Brazil (prevalence of 16.8% for men and 24.4% for women)15, and much higher than that found in the Brazilian Amazon Region, i.e., 14.4% in the Parkatêjê people and 15% in the Aruák people16. Among the risk factors for developing CKD, obesity was the only factor for which there was a statistical difference between the two indigenous groups. 

Our results are likely due to the greater proximity and integration of the study groups with neighboring non-indigenous populations and, consequently, the incorporation of an urban lifestyle. Consequently, changing dietary habits, especially the increased consumption of industrial foods, lead to an increase in chronic non-communicable diseases and cardiovascular risk4,7. In this prospective study, it is likely that younger generations of indigenous people come in contact sooner and have more contact with these aspects of urban life than their ancestors

Our study has limitations for generalizing the results due to the small sample size and its cross-sectional nature, which does not allow for the establishment of the causality of the association. Another limitation stems from the ethnic and cultural diversity of Brazilian indigenous people, which makes the final analysis difficult. Nevertheless, our results are relevant because they present unpublished data on a theme that has been less studied among Brazilian indigenous people. Furthermore, they suggest the influential role of urbanization in the prevalence of CKD and warn of its high prevalence in indigenous communities, which is a situation that occurs with indigenous people in other countries17. Finally, when considering the exclusion criteria of the PAI study (a study designed for a group of generally healthy participants), the low percentage of elderly in the sample (14.3%), the use of only GFR to estimate CKD, the percentage of indigenous people with CKD, and mildly decreased excretory renal function (G2) are significant and cause concern. 

Table 1. Characterization of the study population, according to estimated glomerular filtration rate (estimated glomerular filtration rate <60 and ≥60 mL/min/1.73 m2) and ethnic group (Fulni-ô and Truká indigenous people) (n=280)

CONCLUSION 

A higher degree of urbanization seems to negatively influence the prevalence of kidney disease in Brazilian indigenous people, which is an important concern in assessing the youth in indigenous communities.

REFERENCES 

1. Barreto SM, Ladeira RM, Duncan BB, Schmidt MI, Lopes AA, Benseñor IM, et al. Chronic kidney disease among adult participants of the ELSA-Brasil cohort: association with race and socioeconomic position. J Epidemiol Community Health. 2016;70(4):380-9. https:// doi.org/10.1136/jech-2015-205834

2. Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2012 clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney Int Suppl. 2013;3(1):1-150. Available from: https://kdigo.org/wp-content/ uploads/2017/02/KDIGO_2012_CKD_GL.pdf 

3. Huria T, Pitama SG, Beckert L, Hughes J, Monk N, Lacey C, et al. Reported sources of health inequities in Indigenous Peoples with chronic kidney disease: a systematic review of quantitative studies. BMC Public Health. 2021;21(1):1447. https://doi.org/10.1186/ s12889-021-11180-2 

4. Patriota PVAM, Ladeia AMT, Marques J, Khoury R, Barral A, Cruz AA, et al. Echocardiography and analysis of subclinical cardiovascular diseases in indigenous people living in different degrees of urbanization: project of atherosclerosis among indigenous populations (Pai). Arq Bras Cardiol: Imagem Cardiovasc. 2020;33(4):1-8. https:// doi.org/10.47593/2675-312X/20203304eabc78 

5. Souza Filho ZA, Ferreira AA, Dos Santos J, Meira KC, Pierin AMG. Cardiovascular risk factors with an emphasis on hypertension in the Mura Indians from Amazonia. BMC Public Health. 2018;18(1):1251. https://doi.org/10.1186/s12889-018-6160-8 

6. Chagas CA, Castro TG, Leite MS, Viana MACBM, Beinner MA, Pimenta AM. Estimated prevalence of hypertension and associated factors in Krenak indigenous adults in the state of Minas Gerais, Brazil. Cad Saúde Pública. 2020;36(1):e00206818. https://doi. org/10.1590/0102-311X00206818 

7. Armstrong AC, Ladeia AMT, Marques J, Armstrong DMFO, Silva AML, Morais Junior JC, et al. Urbanization is associated with increased trends in cardiovascular mortality among indigenous populations: the PAI study. Arq Bras Cardiol. 2018;110(3):240-5. https://doi.org/10.5935/abc.20180026 

8. Armstrong A, Marques J, Patriota P, Armstrong D, Negreiro GH, Saad PF, et al. Urbanization and indigenous health in northeast Brazil—concepts of the project of atherosclerosis among indigenous populations (PAI). Navigating complexity: human–environmental solutions for a challenging future [Internet]. 2018. [cited on December 6, 2021]. Available from: https://sheconference2018. weebly.com/uploads/1/6/2/3/16236920/she_5.pdf

9. World Health Organization. World Health Organization: body mass index-BMI. 2021. [cited on June 23, 2021]. Available from: https://www.euro.who.int/en/health-topics/diseaseprevention/%0Anutrition/a-healthy-lifestyle/body-mass-index-bmi

10. Fernanda M. Consolim-Colombo, José Francisco Kerr Saraiva, Maria Cristina Oliveira Izar. Tratado de Cardiologia SOCESP. 4a. SOCESP, editor. 2019.

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