Abstract

Estimating average blood pressure levels and prevalence of arterial hypertension (AH) and associated factors is essential to monitoring health and planning actions to combat noncommunicable diseases (NCDs) in Indigenous peoples in Brazil. This is a cross-sectional study that investigated average blood pressure levels and prevalence of arterial hypertension in 4,680 Indigenous women (aged 18-49 years), using data from the 1^st National Survey of Health and Nutrition of Indigenous Peoples (2008-2009) and associated factors, such as through gamma regression and multilevel logistics. The prevalence of hypertension was 10.7%, varying across macro-regions: North, Northeast, Midwest, and South/Southeast. Women who lived in villages without domestic waste collection and in households without stable income were more likely to have AH. Increasing BMI and age were positively associated with the chances of developing high blood pressure. In the model for DBP, unlike education, the variables stable household income, BMI, and age were positively associated. In the model for SBP, there was a negative association with education, in the medium and high strata of the household goods index and in households with no stable income, and a positive association with the housing indicator, BMI and age.

Key words:
Health of indigenous peoples; Health survey; Women’s health; Arterial hypertension

Introduction

The health profile of Indigenous peoples in Brazil is only partially known, and it is defined by extreme heterogeneity produced by the sociocultural diversity of those peoples, as well as by exposure to distinctive social and environmental determinants in the different regions where they live, and by the limitations in quality and access to services of health surveillance and health care¹1 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 Saude Publica 2019; 36(1):e00206818.. Nonetheless, nationally, as well as internationally, it is possible to recognize a general health standard for these peoples, marked by a high burden of morbidity and mortality by infectious diseases and poor nutrition and health care, especially during childhood, concomitantly with the emergence, among both children and adults, of grievances related to environmental contamination and degradation, to abuse of alcohol and other drugs, to violence and to noncommunicable grievances and diseases (NCDs), including arterial hypertension (AH))²2 Ferreira AA, Souza-Filho ZA, Gonçalves MJF, Santos J, Pierin AMG. Relationship between alcohol drinking and arterial hypertension in indigenous people of the Mura ethnics, Brazil. PLoS One 2017; 12(8):e0182352.

3 Sombra NM, Gomes HLM, Sousa AM, Almeida GS, Souza Filho ZA, Toledo NN. High blood pressure levels and cardiovascular risk among Munduruku indigenous people. Rev Lat Am Enferm 2021; 29:e3477.

4 Souza Filho ZA, Ferreira AA, Santos BD, Pierin AMG. Hypertension prevalence among indigenous populations in Brazil: a systematic review with meta-analysis. Rev Esc Enferm USP 2015; 49(6):1016-26.

5 Schmidt MI, Duncan BB, Silva GA, Menezes AM, Monteiro CA, Barreto SM, Chor D, Menezes PR. Chronic non-communicable diseases in Brazil: burden and current challenges. Lancet 2011; 377(9781):1949-1961.

6 Foulds HJA, Warburton DER. The blood pressure and hypertension experience among North American Indigenous populations. J Hypertens 2014; 32(4):724-734.^-77 Raza Q, Doak CM, Khan A, Nicolaou M, Seidell JC. Obesity and cardiovascular disease risk factors among the indigenous and immigrant Pakistani population: a systematic review. Obes Facts 2013; 6(6):523-535..

AH is one of the main causes of morbidity and mortality on a global scale. This grievance is responsible for 8.5 million deaths around the world by stroke, ischemic cardiac disease, as well as other vascular and kidney diseases. In 2019, the global prevalence of AH standardized by age among adults, aged 30 to 79 years, was 32% (95%CI: 30-34) for women and 34% (95%CI: 32-37) for men⁸8 Almeida JB, Kian KO, Lima RC, Souza MCC. Total and abdominal adiposity and hypertension in Indigenous women in Midwest Brazil. PLoS One 2016; 11(6):e0155528.. In Brazil, nearly 24% of the female population and 17% of the male population had a diagnosis of this condition in 2011⁹9 Carvalho Vidigal F, Bressan J, Babio N, Salas-Salvadó J. Prevalence of metabolic syndrome in Brazilian adults: a systematic review. BMC Public Health 2013; 13:1198.; however, these numbers have increased throughout the years, given that the estimates for 2023 are 26.4% and 29.3% for men and women, respectively¹⁰10 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..

Some studies have indicated that AH is an emerging health issue among Indigenous peoples in different parts of the world⁵5 Schmidt MI, Duncan BB, Silva GA, Menezes AM, Monteiro CA, Barreto SM, Chor D, Menezes PR. Chronic non-communicable diseases in Brazil: burden and current challenges. Lancet 2011; 377(9781):1949-1961.. In the United States, for instance, after the 1980’s, there has been a progressive and heterogeneous growth in the averages of systolic blood pressure (SBP) and diastolic (DBP), as well as in the prevalence of AH among different Indigenous groups, even surpassing, in some cases, the values found for the non-Indigenous population in the same area¹¹11 Mancilha-Carvalho JJ, Silva NAS. The Yanomami indians in the INTERSALT study. Arq Bras Cardiol 2003; 80(3):295-300.^,1212 Oliveira GF, Oliveira TRR, Ikejiri AT, Andraus MP, Galvao TF, Silva MT, Pereira MG. Prevalence of hypertension and associated factors in an indigenous community of central Brazil: a population-based study. PLoS One 2014; 9(1):e86278..

Studies which investigated pressure levels and prevalence of AH among Indigenous peoples in Brazil, indicate that, in a similar manner, there were low tensional levels and an absence of AH among Indigenous peoples in the 1970s⁷7 Raza Q, Doak CM, Khan A, Nicolaou M, Seidell JC. Obesity and cardiovascular disease risk factors among the indigenous and immigrant Pakistani population: a systematic review. Obes Facts 2013; 6(6):523-535., but more recent studies indicate an increase of these issues in several communities, with AH prevalence being higher than 60% in some places¹³13 Rocha AKS, Bós AJG, Huttner E, Machado DC. Prevalência da síndrome metabólica em indígenas com mais de 40 anos no Rio Grande do Sul, Brasil. Rev Panam Salud Publica 2011; 29(1):41-45.

14 Tavares FG, Coimbra Junior CEA, Cardoso AM. Níveis tensionais de adultos indígenas Suruí, Rondônia, Brasil. Cien Saude Colet 2013; 18(5):1399-1409.

15 Basta PC, Orellana JDY, Arantes R. Perfil epidemiológico dos povos indígenas no Brasil: notas sobre agravos selecionados [Internet]. 2012. [acessado 2023 out 13]. Disponível em: http://ds.saudeindigena.icict.fiocruz.br/handle/bvs/4456
http://ds.saudeindigena.icict.fiocruz.br...

16 Coimbra Jr CE, Tavares FG, Ferreira AA, Welch JR, Horta BL, Cardoso AM, Santos RV. Socioeconomic determinants of excess weight and obesity among Indigenous women: findings from the First National Survey of Indigenous People's Health and Nutrition in Brazil. Public Health Nutr 2021; 24(7):1941-1951.

17 Gimeno SGA, Rodrigues D, Canó EN, Lima EES, Schaper M, Pagliaro H, Lafer MM, Baruzzi RG. Cardiovascular risk factors among Brazilian Karib indigenous peoples: Upper Xingu, Central Brazil, 2000-3. J Epidemiol Community Health 2009; 63(4):299-304.^-1818 Coimbra Jr CEA. Saúde e povos indígenas no Brasil: reflexões a partir do I Inquérito Nacional de Saúde e Nutrição Indígena. Cad Saude Publica 2014; 30(4):855-859.. The changes observed in the profile of Indigenous health in recent decades have been attributed to historical contact processes with the surrounding society, increased by the opening of new demographic frontiers, and linked to socioeconomic and environmental changes, conflict and loss of traditional land, sociocultural and lifestyle changes, dependency of the regional market, food insecurity, an increase in the consumption of industrialized food, and barriers in access to health care¹⁹19 Coimbra Jr CEA, Santos RV, Welch JR, Cardoso AM, Souza MC, Garnelo L, Rassi E, Foller Maj-Lis, Horta B. The First National Survey of Indigenous People's Health and Nutrition in Brazil: rationale, methodology, and overview of results. BMC Public Health 2013; 13:52.

20 Montenegro RA, Stephens C. Indigenous health in Latin America and the Caribbean. Lancet 2006; 367(9525):1859-1869.

21 WHO. A global brief on hypertension: silent killer, global public health crisis: World Health Day 2013 [Internet]. 2013. [cited 2023 ago 23]. Disponível em: https://www.who.int/publications/i/item/a-global-brief-on-hypertension-silent-killer-global-public-health-crisis-world-health-day-2013
https://www.who.int/publications/i/item/...

22 Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo JL, Jones DW, Materson BJ, Oparil S, Wright Jr JT, Roccella EJ, Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure, National Heart, Lung, and Blood Institute & National High Blood Pressure Education Program Coordinating Committee. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 report. JAMA 2003; 289(19):2560-2572.^-2323 Anderson I, Robson B, Connolly M, Al-Yaman F, Bjertness E, King A, Tynan M, Madden R, Bang A, Coimbra Jr CEA, Pesantes MA, Amigo H, Andronov S, Armien B, Obando DA, Axelsson P, Bhatti ZS, Bhutta ZA, Bjerregaard P, Bjertness MB, Briceno-Leon R, Broderstad AR, Bustos P, Chongsuvivatwong V, Chu J, Deji, Gouda J, Harikumar R, Htay TT, Htet AS, Izugbara C, Kamaka M, King M, Kodavanti MR, Lara M, Laxmaiah A, Lema C, Taborda AML, LiabsuetrakulT, Lobanov A, Melhus M, Meshram I, Miranda JJ, Mu TT, Nagalla B, Nimmathota A, Popov AI, Poveda AMP, Ram F, Reich H, Santos RV, Sein AA, Shekhar C, Sherpa LY, Skold P, Tano S, Tanywe A, Ugwu C, Ugwu F, Vapattanawong P, Wan X, Welch JR, Yang G, Yang Z, Yap L. Indigenous and tribal peoples' health (The Lancet-Lowitja Institute Global Collaboration): a population study. Lancet 2016; 388(10040):131-157..

Until the First National Health and Nutrition Survey of Indigenous Peoples (1st NHNSIP) in 2008-2009, financed by the World Bank and led by the Brazilian Association of Collective Health²⁴24 Biswas T, Tran N, Thi My Hanh H, Van Hien P, Thi Thu Cuc N, Hong Van P, Tuan KA, Oanh TTM, Mamun A. Type 2 diabetes and hypertension in Vietnam: a systematic review and meta-analysis of studies between 2000 and 2020. BMJ Open 2022; 12(8):e052725., there were no national estimates of the prevalence of different diseases and illnesses affecting Indigenous peoples, at the national and regional level. The estimation of pressure levels and prevalence of AH and associated factors among Indigenous people is a required condition for improving the characterization of the health profile of this population, for following up its tendencies in the next decades, as well as for the planning of healthcare actions and the production of strategies for the prevention and promotion of health²⁵25 Chua EY, Zalilah MS, Haemamalar K, Norhasmah S, Geeta A. Obesity indices predict hypertension among indigenous adults in Krau Wildlife Reserve, Peninsular Malaysia. J Health Popul Nutr 2017; 36(1):24.^,2626 Orellana-Barrios MA, Nuggent KM, Sanchez-Barrientos H, Lopez-Gutierrez JR. Prevalence of hypertension and associated anthropometric risk factors in indigenous adults of Guatemala. J Prim Care Community Health 2015; 6(1):16-20..

The present study aimed to analyze the levels of SBP and DBP, as well as the prevalence of AH and associated factors in a probabilistic, representative sample of Indigenous adult females (aged 18 to 49 years) residing in Indigenous villages in Brazil in four macro-regions - North, Midwest, Northeast, and South/Southeast, using data collected by the 1st NHNSIP²⁴24 Biswas T, Tran N, Thi My Hanh H, Van Hien P, Thi Thu Cuc N, Hong Van P, Tuan KA, Oanh TTM, Mamun A. Type 2 diabetes and hypertension in Vietnam: a systematic review and meta-analysis of studies between 2000 and 2020. BMJ Open 2022; 12(8):e052725., and generating new information at a national and regional level regarding the cardiovascular health of Indigenous peoples in Brazil.

Methodology

This study is based on data collected between 2008 and 2009, time of the 1st NIHNIP, which had a representative complex probabilistic sample of adult Indigenous females in reproductive age (14 to 49 years of age) residing in Indigenous villages, from four macro-regions of the country - North, Northeast, Midwest, and South/Southeast. Additional details on the methodology of the 1st NIHNIP have already been published²⁴24 Biswas T, Tran N, Thi My Hanh H, Van Hien P, Thi Thu Cuc N, Hong Van P, Tuan KA, Oanh TTM, Mamun A. Type 2 diabetes and hypertension in Vietnam: a systematic review and meta-analysis of studies between 2000 and 2020. BMJ Open 2022; 12(8):e052725..

Blood pressure (BP) of adult women (aged 18 to 49 years) was measured according to The Seventh Report of the Joint Committee (JNC 7)²⁷27 Julião NA, Souza A, Guimarães RRM. Tendências na prevalência de hipertensão arterial sistêmica e na utilização de serviços de saúde no Brasil ao longo de uma década (2008-2019). Cien Saude Colet 2021; 26(9):4007-4019., following protocols to ensure accuracy, such as relative rest for 10 minutes, abstinence of tobacco or coffee for at least 30 minutes before the measurements, and reduction of external stimuli, such as people talking and playing; the participants were placed in a sitting position, the tensiometer was installed on the left wrist and kept at heart level. Whenever necessary and possible, the participants removed clothing items, bracelets, or other accessories that could interfere in the precision of the readings. In case of issues preventing measurements on the left wrist, measurements were taken on the right wrist. Such an event only occurred in 1.1% of the measurements, with no divergence between the regions.

Two BP measurements were taken: the first was obtained after the seven initial questions in the interview, and the second took place at the end of the interview, thus ensuring a minimum interval of ten minutes between measurements. The BP value of each participant was defined as the average between the two measurements. The average values were classified based on criteria for AH, as defined by the JNC 7²⁷27 Julião NA, Souza A, Guimarães RRM. Tendências na prevalência de hipertensão arterial sistêmica e na utilização de serviços de saúde no Brasil ao longo de uma década (2008-2019). Cien Saude Colet 2021; 26(9):4007-4019.. Therefore, the values classified as normal for Systolic Blood Pressure (SBP) and Diastolic Blood Pressure (DBP) were: SBP < 140 mmHg and DBP < 80 mmHg. Values of SBP ≥ 140 mmHg and/or DBP ≥ 90 mmHg were classified as AH. Considering the possibility of individuals with an existing AH diagnosis and using antihypertensive medication, who presented normal levels of de SBP and DBP at the time of the interview, we considered the reports of antihypertensive medication use as AH, regardless of the BP measurements. The proportion of cases with missing information regarding use of antihypertensive medication was 0.4% for the entire group of macroregions, with a higher proportion found in the North (1.4%), followed by the Midwest (0.3%) and South/Southeast (0.2%). This situation was not verified in the Northeast.

The main component analysis (MCA) was used to produce the following variables related to socioeconomic life conditions: (a) index of owned goods, based on the quantities of industrialized, durable goods present in each household (the first component explained 19% of the variance, self-value of 3.56); (b) housing conditions index, based on the quality of the floor, walls, roof, availability of electricity and cooking fuel (the first component explains 48.0% of the variance, self-value of 1.44); and (c) sanitation index, based on the availability of a place to defecate, having trash management, having water for human consumption and availability at home of filtered water for drinking (the first component explained 56.5% of the variance, self-value of 0.63). The households received scores based on the sum of the contribution of each item, multiplied by the amount of each item present in the household, and then households were classified according to the tertiles of the general distribution, considering the four macroregions together as one. In each case, the first tertile indicates a lower score for the index, which represents less industrialized, durable goods, less access to materials and living resources produced by the market, and poorer sanitation conditions²⁰20 Montenegro RA, Stephens C. Indigenous health in Latin America and the Caribbean. Lancet 2006; 367(9525):1859-1869..

The individual variables of the females who participated in this study include age group and years of education. Other variables analyzed in the study were self-explanatory and are presented in the tables.

Statistical analyses

Initially, we conducted the descriptive statistical analysis of SBP and DBP and of the prevalence of AH, stratified by macroregion and for the entire country. We then employed multilevel models with two levels, Village and Region, following a process of selection of variables with a hierarchized approach to investigate associations between these outcomes and the exposure variables of the individual, household, and village dimensions.

To analyze the factors associated with SBP and DBP, whose distributions presented positive asymmetry, multilevel Gamma regression with identity connection function was used. To analyze the factors associated with AH, multilevel logistic regression was applied. The phase of selection of variables to be maintained in the final adjusted model was conducted in a detailed manner, beginning with a crude analysis for the different variable dimensions - village, household, and women. Variables with a p-value below 0.20 were included in the multiple analyses, while the final model maintained those with a significance level (p-value) below 0.05.

Three multiple models were built for each outcome in the study, given that Model 1 exclusively included the variables related to the village (distal); Model 2 included the variables related to village and household (intermediate); and Model 3, which incorporated the variables related to the characteristics of the woman (proximal) into Model 2. It is important to remember that in the models involving SBP and DBP, women who used antihypertensive medication were excluded. The multilevel approach sought to conduct a broad analysis of the associations between cardiovascular outcomes and different demographic variables, as well as socioeconomic, eating, and nutritional variables, taking into consideration the living context in the villages and the households.

The study was approved by the National Research Ethics Committee (Comissão Nacional de Ética em Pesquisa - CONEP) and by the National Indigenous Foundation (Fundação Nacional do Índio - FUNAI). In each visited community, the team of researchers had meetings with leaders and other members of the community to present and explain the objectives and procedures of the study. At that time, we made it explicit that the participation of communities, households, and individuals was volunteer. The free and informed terms of consent were obtained through the signatures of leaders and/or other community representatives of the villages that chose to participate in the investigation.

Results

In the present study, 4,680 Indigenous women, aged 18 to 49 years, participated and were evaluated in terms of the cardiovascular outcomes of interest. The values of the median for SBP and DBP were 111.5mmHg and 71.0mmHg, respectively, in the group of Indigenous women in the target age group in Brazil. For SBP, as well as for DBP, it was observed that only the values obtained for women in the North macroregion (SBP:108.0mmHg; DBP: 67.5mmHg) were below the corresponding national Indigenous medians. The highest medians of SBP and DBP were those of the South/Southeast (SBP: 115.5mmHg; DBP:74.0 mmHg) and of the Midwest (SBP:115.0mmHg; DBP:74.5 mmHg), followed by the Northeast (SBP:111.5mmHg; DBP:72.0mmHg). The distributions of SBP and DBP according to macroregions are shown in Figure 1. There are significant differences in the distributions of SBP and DBP values, with higher medians in the Midwest and South/Southeast macroregions, which stand out as the regions with a higher variation between the values measured. Outliers were identified in all of the macroregions.

The prevalence of AH in adult Indigenous women, in reproductive age, in Brazil, was 10.7%. Heterogeneity can be noticed in prevalence according to macroregions, the North being the lowest (4.0%), and the Midwest and the South/Southeast being the highest, which proved to be similar and 4.5-fold higher than the prevalence of the North region (Table 1).

he analysis of the prevalence of AH by age group shows a consistent increase in the proportion of women with AH as age increases, considering the tendency observed in all of the macroregions, although with lower magnitude in the North region. The highest prevalence was found for the age group of 45 to 49 years of age, with macro-regional variation ranging from 11.3%, in the North, to 52.9%, in the South/Southeast. It is striking that the Midwest and South/Southeast macro-regions had a high prevalence (> 20%) even in the age bracket of 30 to 34 years of age (Table 1).

In the crude analysis, we verified the following associations with outcomes of the study, with significance level (p-value) lower than 0.20: the prevalence of AH was associated negatively with the practice of domestic fishing and hunting, education, stable income, and the presence of outside donations, and positively with BMI and age. The SBP and the DBP were negatively associated with collective cattle raising; with an index of owned goods, living conditions and sanitation; and with stable income in the household and education, and positively with BMI and age. Additionally, SBP was positively associated with the presence of outside donations (Table 2).

In the adjusted analysis, the variables which remained negatively associated with the prevalence of AH were domestic gathering of food, stable income, and education. Meanwhile, the positively associated variables were BMI and age. Notably, Indigenous women residing in villages where domestic gathering was not practiced and in households that had no stable income, had chances of having AH, 1.77 and 1.25-fold higher than those of women residing in villages where domestic gathering was practiced and in households with stable income, respectively. The increase in one unit in the values of BMI and age corresponded to an increase of 9% and 11% in the chances of having AH, respectively. By contrast, as the number of years of education increased, a significant gradient, was noticed in terms of a decrease in the chances of having AH, of 24%, 31%, and 68%, respectively, for strata 1 to 4 years, 5 to 9 years, and 10 or more years of study, in comparison to those who were unschooled (Table 3).

In the adjusted analysis, the variables that remained negatively associated with SBP were the index of owned goods, living conditions, stable household income, and education, while the positively associated variables were BMI and age. However, the living conditions index and stable income lost statistical significance in Model 3 (Table 3). An average reduction was noticed, of 1.31 mmHg and of 1.94 mmHg, respectively, in the second and third tertiles of the index of owned goods, in comparison with the first tertile, which corresponds to less owned goods. Likewise, a decline was noticed in SBP, of 2.19 mmHg, 3.45 mmHg, and 4.37 mmHg, respectively, in strata 1 to 4, 5 to 9, and 10 or more years of study, when compared to those with no schooling. By contrast, there was an increase of 0.62mmHg and 0.29mmHg, as BMI and age were increased in one unit, respectively.

In this analysis, DBP remained negatively associated with education and positively associated with stable household income, BMI, and age; however, stable income lost statistical significance in Model 3 (Table 3). The DBP had reductions of 1.19 mmHg, 2.31 mmHg, and 2.96 mmHg, respectively, in strata 1 to 4, 5 to 9, and 10 or more years of education, when compared with the unschooled category. On the other hand, increases of 0.38mmHg and 0.17mmHg, were observed, with an increase of one unit in BMI and age, respectively.

Discussion

The results of this study are representative of the population of adult Indigenous women (aged 18 to 49 years) in Brazil and in four macroregions, and are an unprecedented initiative to estimate the magnitude of AH in this population, revealing the regional inequalities regarding BP levels and the prevalence of AH, as well as identifying factors associated with the increase in BP levels and in the prevalence of AH. This study therefore provides a new and broad view on NCDs, with focus on AH among Indigenous peoples in Brazil. Internationally, scientific literature has indicated health vulnerabilities of Indigenous peoples resulting from socioeconomic, demographic, sanitary, environmental, and territorial conditions, which are unfavorable⁵5 Schmidt MI, Duncan BB, Silva GA, Menezes AM, Monteiro CA, Barreto SM, Chor D, Menezes PR. Chronic non-communicable diseases in Brazil: burden and current challenges. Lancet 2011; 377(9781):1949-1961.^,2525 Chua EY, Zalilah MS, Haemamalar K, Norhasmah S, Geeta A. Obesity indices predict hypertension among indigenous adults in Krau Wildlife Reserve, Peninsular Malaysia. J Health Popul Nutr 2017; 36(1):24., and has also indicated the emergence of NCDs in these populations, including AH among Indigenous women¹¹11 Mancilha-Carvalho JJ, Silva NAS. The Yanomami indians in the INTERSALT study. Arq Bras Cardiol 2003; 80(3):295-300.^,1313 Rocha AKS, Bós AJG, Huttner E, Machado DC. Prevalência da síndrome metabólica em indígenas com mais de 40 anos no Rio Grande do Sul, Brasil. Rev Panam Salud Publica 2011; 29(1):41-45.^,1717 Gimeno SGA, Rodrigues D, Canó EN, Lima EES, Schaper M, Pagliaro H, Lafer MM, Baruzzi RG. Cardiovascular risk factors among Brazilian Karib indigenous peoples: Upper Xingu, Central Brazil, 2000-3. J Epidemiol Community Health 2009; 63(4):299-304.^,2828 Brasil. Ministério da Saúde (MS). Vigitel Brasil 2021 - estimativas sobre frequência e distribuição sociodemográfica de fatores de risco e proteção para doenças crônicas [Internet]. 2021. [acessado 2023 ago 23]. Disponível em: https://www.gov.br/saude/pt-br/centrais-de-conteudo/publicacoes/svsa/vigitel/vigitel-brasil-2021-estimativas-sobre-frequencia-e-distribuicao-sociodemografica-de-fatores-de-risco-e-protecao-para-doencas-cronicas/view
https://www.gov.br/saude/pt-br/centrais-... . Such patterns are consonant with our results, insofar as they indicate that AH is an emerging health issue among Indigenous peoples in Brazil.

In a systematic review on BP levels and AH in Indigenous populations in North America, published in 2014, Foulds and Warburton¹¹11 Mancilha-Carvalho JJ, Silva NAS. The Yanomami indians in the INTERSALT study. Arq Bras Cardiol 2003; 80(3):295-300. realized that, since 1980, there has been a progressive increase in the prevalence of AH through the decades, which had not been seen in the period pre-1980, and which have affected distinctive native populations, such as the First Nations/American Natives, and the Inuit, the natives of Alaska. The Inuit/Alaska Natives presented a high prevalence of AH, in the magnitude of 55.1% even before the 1980’s. After 1980, those proportions remained stable, but more recently, the averages of SBP and DBP have shown continuous increases. These fluctuations in BP levels indicate notable changes in cardiovascular health of the Inuit/Alaska Natives over time. Considering this health scenario, which is heterogenous and in transition, affecting native communities at the global level, a pressing question regarding AH emerges. Although there are communities with a low or even nonexistent prevalence of hypertension, records indicate that some have a prevalences of above 50%¹¹11 Mancilha-Carvalho JJ, Silva NAS. The Yanomami indians in the INTERSALT study. Arq Bras Cardiol 2003; 80(3):295-300.^,1616 Coimbra Jr CE, Tavares FG, Ferreira AA, Welch JR, Horta BL, Cardoso AM, Santos RV. Socioeconomic determinants of excess weight and obesity among Indigenous women: findings from the First National Survey of Indigenous People's Health and Nutrition in Brazil. Public Health Nutr 2021; 24(7):1941-1951.^,2929 Kramer CK, Leitão CB, Viana LV. 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. Lancet 2022; 400(10368):2074-2083.^,3030 Bloch KV, Coutinho ESF, Lôbo MSC, Oliveira JEP, Milech A. Pressão arterial, glicemia capilar e medidas antropométricas em uma população Yanomâmi. Cad Saude Publica 1993; 9(4):428-438..

Our study estimated a national average AH prevalence of 10.7% in adult Indigenous females of reproductive age, with considerable variations between macroregions. The North region had the lowest prevalence, while the South/Southeast and Midwest macroregions had the highest prevalence, 4.5-fold higher than the prevalence in the North. When comparing the prevalence of AH in Indigenous women, found in this study, and the general female population of Brazil above 18 years of age, the Indigenous women presented a prevalence that is equivalent to half of the 23.0% found for Brazilian women in general in the initial year of the study, 2008³¹31 Cardoso AM, Mattos IE, Koifman RJ. Prevalence of risk factors for cardiovascular disease in the Guaraní-Mbyá population of the State of Rio de Janeiro. Cad Saude Publica 2001; 17(2):345-354.^,3232 Salvo VLMA, Rodrigues D, Baruzzi RG, Pagliaro H, Gimeno SGA. Perfil metabólico e antropométrico dos Suyá: Parque Indígena do Xingu, Brasil Central. Rev Bras Epidemiol 2009; 12(3):458-468..

The magnitude of prevalence found in our study is similar to the results of 11% reported by a systematic review and meta-analysis about the metabolic health of Indigenous adults in Brazil³³33 Bresan D, Bastos JL, Leite MS. Epidemiology of high blood pressure among the Kaingang people on the Xapecó Indigenous Land in Santa Catarina State, Brazil, 2013. Cad Saude Publica 2015; 31(2):331-344.. However, such a similarity must be considered with caution, since the mentioned review estimated the prevalence for both genders together, for all ages, and regardless of residence in villages. By contrast, our estimates are restricted to adult Indigenous women of reproductive age who live in villages. Moreover, this review is based on studies conducted in a relatively small number of Indigenous communities in the country. Brazil has one of the most expressive social diversities on the planet, and shows considerable heterogeneity in the prevalence of AH between different communities and regions, with values ranging from 30% in the South, to discrete values of around 1% found for Indigenous communities in the North region. Older studies indicated the absence of AH among those communities, a phenomenon that is likely related to improvements in diagnosis and to the emergence of NCDs over time³³33 Bresan D, Bastos JL, Leite MS. Epidemiology of high blood pressure among the Kaingang people on the Xapecó Indigenous Land in Santa Catarina State, Brazil, 2013. Cad Saude Publica 2015; 31(2):331-344.. Other studies have reported the prevalence of AH among Indigenous people that were lower than that found in this study¹⁶16 Coimbra Jr CE, Tavares FG, Ferreira AA, Welch JR, Horta BL, Cardoso AM, Santos RV. Socioeconomic determinants of excess weight and obesity among Indigenous women: findings from the First National Survey of Indigenous People's Health and Nutrition in Brazil. Public Health Nutr 2021; 24(7):1941-1951.^,3434 Meyerfreund D, Goncalves C, Cunha R, Pereira AC, Krieger JE, Mill JG. Age-dependent increase in blood pressure in two different Native American communities in Brazil. J Hypertens 2009; 27(9):1753-1760.

35 Carvalho JJ, Baruzzi RG, Howard PF, Poulter N, Alpers MP, Franco LJ, Marcopito LF, Colher VJ Ar T, Elliott P. Blood pressure in four remote populations in the INTERSALT Study. Hypertension 1989; 14(3):238-246.

36 Popkin BM, Adair LS, Ng SW. Global nutrition transition and the pandemic of obesity in developing countries. Nutr Rev 2012; 70(1):3-21.^-3737 Coimbra CE, Chor D, Santos RV, Salzano FM. Blood pressure levels in Xavánte adults from the Pimentel Barbosa Indian Reservation, Mato Grosso, Brazil. Ethn Dis 2001; 11(2):232-240.. Other studies have found a higher prevalence, as in the case of those conducted with the Mura people in the Amazon region (27.8%)¹⁵15 Basta PC, Orellana JDY, Arantes R. Perfil epidemiológico dos povos indígenas no Brasil: notas sobre agravos selecionados [Internet]. 2012. [acessado 2023 out 13]. Disponível em: http://ds.saudeindigena.icict.fiocruz.br/handle/bvs/4456
http://ds.saudeindigena.icict.fiocruz.br... , with the Krenak (27.6%)³⁸, the Kaingang from Santa Catarina (40.7%)³⁹, and the Tupinikin from Espírito Santo (20.8%) (for both genders)⁴⁰.

Therefore, our SBP and DBP averages and AH prevalence should be seen as estimates restricted to female Indigenous women of reproductive age, although they are representative of the diversity of Indigenous populations living in villages, considering that it was conducted with a probabilistic sample of adult Indigenous women of reproductive age and residing in villages in Brazil and in the four analyzed macroregions. This population cut-off results in estimates of a relatively low prevalence of AH when compared to other studies conducted with Indigenous populations and considering both genders, as well as studies considering higher age groups and populations that do not live in villages and on Indigenous lands¹⁵15 Basta PC, Orellana JDY, Arantes R. Perfil epidemiológico dos povos indígenas no Brasil: notas sobre agravos selecionados [Internet]. 2012. [acessado 2023 out 13]. Disponível em: http://ds.saudeindigena.icict.fiocruz.br/handle/bvs/4456
http://ds.saudeindigena.icict.fiocruz.br... ^,3333 Bresan D, Bastos JL, Leite MS. Epidemiology of high blood pressure among the Kaingang people on the Xapecó Indigenous Land in Santa Catarina State, Brazil, 2013. Cad Saude Publica 2015; 31(2):331-344.^,38. Since the associations between AH and age, sex, and residency in urban areas are widely known, the inclusion of these segments in the study would result in considerably higher AH prevalence in comparison to what we found²⁶26 Orellana-Barrios MA, Nuggent KM, Sanchez-Barrientos H, Lopez-Gutierrez JR. Prevalence of hypertension and associated anthropometric risk factors in indigenous adults of Guatemala. J Prim Care Community Health 2015; 6(1):16-20.^,3434 Meyerfreund D, Goncalves C, Cunha R, Pereira AC, Krieger JE, Mill JG. Age-dependent increase in blood pressure in two different Native American communities in Brazil. J Hypertens 2009; 27(9):1753-1760.^,3636 Popkin BM, Adair LS, Ng SW. Global nutrition transition and the pandemic of obesity in developing countries. Nutr Rev 2012; 70(1):3-21.^,39.

Our findings reveal different factors associated with BP levels and with AH among adult Indigenous women of reproductive age in Brazil. The absence of a stable family income, combined with the condition of residing in villages, where the consumption of food from hunting, fishing, and gathering is non-existent, appears as a context that increases the probability of AH. This relationship suggests a connection between adverse subsistence conditions and food insecurity, resulting in a scarcity of food of satisfactory quality and quantity, and consequently in the consumption of industrialized and ultra-processed foods, which cause weight gain, obesity, and deterioration of cardiovascular health, in the form of increased pressure levels and the prevalence of AH. At the same time, it is interesting to notice that education emerges as a protective factor against AH, emphasizing the importance of access to education in terms of favoring health promotion and the prevention of NCDs.

Other studies conducted with Indigenous peoples stood out for investigating the relationship between the way of life of those populations and BP, as in the case of the international study INTERSALT⁴¹. Conducted in the end of the 1980’s, this study aimed to systematically investigate relationships between the ingestion of sodium (Na+) and potassium (K+) and BP levels, as well as other variables, in 52 different populations from 32 countries. The study included in its sample different Indigenous groups, such as the Yanomámi from the Amazon, who stood out in that scenario for presenting exceptionally low BP levels and an absence of AH diagnoses. Moreover, a striking positive association was identified between the ingestion of sodium and levels of BP, a result that diverged from patterns observed in other populations¹⁶16 Coimbra Jr CE, Tavares FG, Ferreira AA, Welch JR, Horta BL, Cardoso AM, Santos RV. Socioeconomic determinants of excess weight and obesity among Indigenous women: findings from the First National Survey of Indigenous People's Health and Nutrition in Brazil. Public Health Nutr 2021; 24(7):1941-1951.. Those findings reveal the importance of considering cultural and environmental factors as related to BP, and proved the need for individualized approaches when investigating cardiovascular health in different population groups, as well as to understand more completely how it is determined.

In this context, it is worthwhile to highlight the negative repercussions for cardiovascular health related to substantial changes in eating patterns and lifestyle, which are associated with an alarming increase in the prevalence of obesity and overweight⁴². Results from this same previously published national inquiry showed evidence of a high prevalence of obesity and overweight among Indigenous women in our study²⁰20 Montenegro RA, Stephens C. Indigenous health in Latin America and the Caribbean. Lancet 2006; 367(9525):1859-1869.. Such an issue is extremely relevant, considering that we identified an increase in AH prevalence and high BP levels, which relate to increases in BMI, as observed in other studies about Indigenous groups⁶6 Foulds HJA, Warburton DER. The blood pressure and hypertension experience among North American Indigenous populations. J Hypertens 2014; 32(4):724-734.^,1313 Rocha AKS, Bós AJG, Huttner E, Machado DC. Prevalência da síndrome metabólica em indígenas com mais de 40 anos no Rio Grande do Sul, Brasil. Rev Panam Salud Publica 2011; 29(1):41-45.^,1515 Basta PC, Orellana JDY, Arantes R. Perfil epidemiológico dos povos indígenas no Brasil: notas sobre agravos selecionados [Internet]. 2012. [acessado 2023 out 13]. Disponível em: http://ds.saudeindigena.icict.fiocruz.br/handle/bvs/4456
http://ds.saudeindigena.icict.fiocruz.br... ^,38. In other words, the association between obesity and AH observed in the present study most likely reflects changes in eating patterns, physical activity patterns, and environmental conditions, which are part of the process of nutritional and epidemiological transition that these populations had to face when coming into contact with the surrounding society.

When we consider the limitations of this study, we should mention that the cross-sectional approach in this study does not allow for the attribution of causality to the investigated relationships. Moreover, it is important to highlight the fact that the 1st NHNSIP was focused on investigating maternal and infant health in the Indigenous population of Brazil, thereby excluding adult men, women over 50 years of age, and individuals residing outside of Indigenous villages and lands, thus restricting the results to women residing in Indigenous reservations officially recognized by the federal government and that were part of the Indigenous Health Subsystem (SASI-SUS).

Regarding the strengths of this study, we highlight that it was conducted with the objective of providing evidence to support healthcare for Indigenous peoples covered by the Indigenous Healthcare Subsystem, especially in terms of mother and infant health, and in terms of nutritional and eating surveillance. Our findings are, therefore, applicable for the planning of health promotion and care actions within this segment, which is of particular interest, considering its health vulnerabilities. This study had a nationwide coverage and was based on a probabilistic sample of the population of women residing in villages, which is representative of four macroregions, with no loss of precision, and even included populations that had never been studied before. The estimates generated by this study are, therefore, robust and generalizable for Indigenous populations of the macroregions and for the country, and can be used as parameters for future comparisons of AH tendencies in these populations, and for the planning of health care and health promotion.

Future studies should consider the inclusion of other age groups, of the male sex, and of populations that do not reside in Indigenous villages and lands, in order to provide a more complete understanding of the burden of AH and the factors which influence the cardiovascular health of the Indigenous populations in Brazil. Carrying out investigations in specific communities reinforces the need to consider the cultural and geographic context in order to achieve a more precise and sensible understanding of the health determinants in those historically marginalized communities. The reproduction of studies such as this, in different contexts and scales, is essential in order to enable the monitoring of tendencies of NCDs among Indigenous peoples, and to guide health policies and strategies that seek to reduce inequalities and improve the health and wellbeing of these populations, respecting their cultural and socioeconomic specificities, as well as their constitutionally established rights to land and access to health.

Acknowledgements

The authors wish to thank the support and assistance provided by Indigenous leaders and community members of the studied villages, as well as to the help of local staff from the National Indigenous Foundation (FUNAI) and of the National Health Foundation (FUNASA). The administrative support provided by the team of the Brazilian Association of Collective Health (Associação Brasileira de Saúde Coletiva - ABRASCO) considerably facilitated our trips and financial logistics.

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