Cardiovascular risk factors with an emphasis on hypertension in the Mura Indians from Amazonia

The Brazilian indigenous population is currently undergoing a process of epidemiological transition with the occurrence of communicable diseases, malnutrition and non-communicable chronic diseases. The First National Survey of Indigenous People’s Health and Nutrition in Brazil showed that 15.8% of the indigenous population had obesity, 30.3% were overweight, and 13.2% had hypertension [1]. The changes in indigenous health are related to the processes of change in culture, habits and lifestyles and the greater access to technological resources and industrialized food products [2–5]. The origin of these changes lies in the historical process of socioeconomic and environmental changes, mainly resulting from the opening of demographic frontiers and the loss of indigenous territories [5]. As a result, indigenous peoples had more exposure to cardiovascular risk factors and cardiovascular diseases, which are currently the main cause of morbidity and mortality in the world [6].

In addition to being a public health problem, hypertension is one of the main risk factors for the development of cardiovascular diseases [7]. According to the World Health Organization’s 2014 Report, cardiovascular diseases accounted for 31% of the mortality in Brazil [8]. The prevalence of hypertension in the Brazilian indigenous population is quite varied; it is non-existent in the Yanomami Indians [9] and is prevalent in 29.5% of the indigenous reservation population of Aldeia Jaguapiru [10]. A meta-analysis review study that included 23 publications on the prevalence of hypertension among Brazilian natives reported that between 1966 and 2012, the prevalence of hypertension increased by 6.2%, with a 12% increase in the chance of an Indian presenting with hypertension in each year of the evaluation period [11]. In the indigenous populations in Brazil, other cardiovascular risk factors were also found, such as overweight [1, 12–14], increased waist circumference [15], diabetes mellitus [12, 13], hypertriglyceridemia [14, 15], increased waist-to-hip ratio [16], hypercholesterolemia [17, 18], sedentary lifestyle [19], smoking [20], and the ingestion of alcoholic beverages [21, 22].

Amazonas, one of the 27 federative units in Brazil, is the largest state, with an area of 1,559,159,148 km², and its indigenous population consisted of 183,514 individuals in 2010 [23]. Three studies on cardiovascular risk factors were performed among natives in the state of Amazonas. The first study, from 1992, was with the Yanomami ethnic group from the villages of Maturacá and Maiá, in northwestern Amazonas [24]. The second study [1], conducted in 2013 and titled “The First National Survey of Indigenous People’s Health and Nutrition in Brazil”, has not yet released results stratified by ethnicity and state. The third study involved the Indians of the Upper Rio Negro and Sateré-Mawé ethnic groups who live in urban areas of Manaus, the main city of Amazonas [25].

Data from the Brazilian demographic census of 2010 [23] indicated that the indigenous population includes 896,900 individuals, representing 0.47% of the Brazilian population; of these, 36.2% lived in urban areas, and 63.8% lived in rural areas. The North Region stands out as the area with the largest indigenous population in Brazil, or 342,000 indigenous people. In this context, the Mura Indians represent the 13th largest ethnic group in Brazil, with approximately 12,479 Indians living in villages and in urban areas, due to the effect of Amazonia’s territorialisation policies in favour of extractive activities, and 7769 indigenous people live outside indigenous lands. Additionally, due to these circumstances, which differ from the Mura of the other ethnic groups studied, the indigenous people are more exposed to the substitution of Western habits and lifestyles for their culture and customs. Thus, the epidemiological transition from infectious diseases to non-communicable diseases would have greater magnitude and transcendence. Therefore, it is important to understand the health data of these populations for the creation of public policies that meet the current needs of the indigenous people. Thus, the objective of the present study was to evaluate the prevalence of cardiovascular risk factors, with an emphasis on hypertension, in Mura Indians living in the municipality of Autazes in the state of Amazonas in northern Brazil.

A cross-sectional population-based study was conducted among Mura Indians living in the city of Autazes in the state of Amazonas, located in northern Brazil. The city of Autazes is located in the central region of the state of Amazonas, far from the capital Manaus, approximately 110 km in length and 218 km inland by waterway. Autazes was chosen for its large contingent of indigenous people, composed of three ethnic groups: Apurinã, Mura and Munduruku, the largest of which is the Mura ethnic group. In the state of Amazonas, the Mura ethnic group includes 60% of the population served by the special indigenous health district Manaus. The study was carried out in two poles of the city of Autazes: Pantaleão and Murutinga.

Anthropometric and laboratory data (Table 4) showed that the majority of the studied Indians had increased neck circumference [60.2% (95% CI: 55.7–64.7%)], were overweight [57.1% (95% CI: 46.7–67.6%)] and had high body fat [69.3% (95% CI: 65.0–73.5%)]. Nearly half had increased waist circumference [48.6% (95% CI: 44.0–53.2%)]. Cholesterol levels were elevated by 27.5% (95% CI: 21.3–33.7%) and triglycerides by 23.5% (95% CI: 19.6–27.4%), and 3.0% of the sample presented diabetes mellitus (95% CI: 1.8–5.1%).

In relation to non-hypertensive individuals, the indigenous hypertensive individuals were (p ≤ 0.05) older, and a higher proportion of individuals lived with their partners, were retired, and had lower levels of schooling and higher family income. The indigenous people living in urban areas had a higher prevalence of hypertension than did those living in rural areas (Table 1). With regard to personal history, hypertensive patients reported (p ≤ 0.05) a greater frequency of heart problems, stroke, diabetes mellitus and dyslipidaemia. With regard to habits and lifestyles, the hypertensive patients had a lower prevalence of smoking, a higher frequency of the use of animal fat in the preparation of meals, a lower frequency of vegetable oil use, and a lower frequency of the addition of salt to already-prepared meals (Table 2).

The findings from the present study showed that Indian participants with hypertension had a high prevalence of hypertension, increased neck circumference, elevated quantities of body fat, sedentary lifestyles, increased waist circumference, and elevated cholesterol and triglycerides. These findings may be associated with the adoption of Western habits and lifestyles by the Mura Indians, due to the loss of their territories from the policies of expansion of agricultural frontiers and extractivism in the northern region of Brazil [1–5].

Notably, a sedentary lifestyle, overweight and obesity, dyslipidaemia, and hypertension [1, 4, 6] were the most prevalent cardiovascular risk factors among the Mura Indians (52.8%); this finding was higher than that observed between the Kaingang and Guaraní natives (45.3%) [17] and in a data survey from the general population of all Brazilian capitals (46.0%) [37]. The Mura Indians have adopted a sedentary lifestyle, mainly due to the ease of access to technology. Previously, they paddled through rivers in canoes, and they are now travelling in motor boats. Another alarming finding was the high intake of alcoholic beverages (40.2%), which was a higher frequency than that observed among indigenous people in the Jaguapiru village (31.1%) [10], in the Kaingang Indians (29.9%) [22] and among Guaraní, Kaiowá and Terena natives [14].

The present study showed that 26.6% of the Indians studied from the Mura ethnic group of the city of Autazes, Amazonas, Brazil, had hypertension. The prevalence among the Mura Indians was higher than that of other studies with indigenous populations, including the Xavante (17.2–17.5%) [16] and Tupinikim (20.8%) Indians [20], and close to that observed among the Kaingang Indians (26.8%) [18] and the indigenous people of the Jaguapiru village (29.5–29.7%) [10, 12]. The variations observed in the prevalence of hypertension may be related to different habits and lifestyles [15], disparities in the criteria for the definition of hypertension [16] and proximity to urban areas [7, 16, 22]. The proximity to urban areas seems to be the most plausible hypothesis. The findings of the present study showed higher prevalence among indigenous people in urban areas than among those in rural areas. The proximity and the contact with urban areas expose the natives to the adoption of unhealthy habits and lifestyles. Thus, the lowest prevalence was observed among the Xavante and Tupinikim Indians, which is probably attributed to their residing in indigenous reserves, while the highest prevalence was observed in ethnicities close to urban settlements [16, 19]. A systematic review with a meta-analysis of publications from 1980 to 2010 examining the prevalence of hypertension in the general population of Brazil showed a decrease in the prevalence of hypertension, from 36.1 to 28.1% [38]. Thus, the 26.6% finding of the Mura Indians is close to the findings of data from population-based studies in Brazil. This prevalence of hypertension in the Mura Indians reinforces, once again, the relationships among hypertension; the process of accelerated urbanization; the progressive increase in life expectancy; the changes in dietary patterns; the excessive consumption of foods rich in saturated fat; and the risk factors for hypertension, diabetes and obesity.

We also highlight the probable influence of the socioeconomic context, with a predominance of low-income individuals, and the fact that the majority of the Indians belong to the less-favoured classes (D-E). In the sample studied, the majority of Mura Indians (60.2%) reported participating in some direct income distribution programme by the federal government, especially the Bolsa Família Program (97.8%). Researchers investigating other ethnicities also observed this phenomenon, as among the Terena indigenous people, with 71.4% of the families included in a government social programme [39]; among the Guaraní ethnic group from Dourados, Mato Grosso do Sul, 84.2% of the indigenous families benefited from the Bolsa Família (Family Allowance) programme [40]. Often, social benefits are the main and only source of income for indigenous families. Indigenous people are considered to have greater social vulnerability due to the high percentage of families living in poverty and extreme poverty, which may contribute to worsening health conditions.

The results showed that the hypertensive Indians had a higher mean age than did the non-hypertensive subjects. This finding was expected because there is a direct and linear association between ageing and the prevalence of hypertension. The prevalence of hypertension was 68% in a meta-analysis review study that included 13,978 elderly people in Brazil [41]. Increasing age was also associated with hypertension in a study with indigenous people of the Guaraní, Kaiowá and Terena ethnic groups of the Jaguapiru village [10]. The results were expected to show that hypertension, a non-transmissible chronic disease, was associated with lifetime exposure to modifiable and intermediate risk factors for cardiovascular diseases.

The mean body mass index in the Mura Indians was high (26.65), and there was a statistically significant difference between the hypertensive and non-hypertensive Indians. The positive association between hypertension and body weight gain and obesity is a reality in non-indigenous [42–44] and indigenous [12, 18, 20] populations, because these modifiable risk factors act by increasing blood volume as well as decreasing peripheral vascular resistance, favouring an increase in systemic blood pressure. In addition, they may also cause increased ventricular filling pressure, which may result in increased vessel wall stress, diastolic dysfunction, and left ventricular hypertrophy, resulting in compromised cardiac work and the promotion of early signalling mechanisms for changes cellular and atheroma formation, thus bypassing this hypothesis. Among these variables, nutritional assessment, hypertensive Indians showed higher values for neck circumference; waist-hip ratio; conicity index; body age in relation to the actual age; and the percentage of body fat. The evaluation of all these anthropometric parameters in Brazilian indigenous peoples is an unprecedented fact.

Regarding food consumption, no differences were observed in the average food frequency score among hypertensive and non-hypertensive natives. However, a low frequency of in natura consumption was observed in both groups, as well as an intermediate score in the consumption of industrialized foods in hypertensive and non-hypertensive Indians. However, in relation to the origin of food, the Indians predominantly bought their food and reported a lower proportion of food that was collected, home-grown or from home-raised animals. These findings signal a transition in the food patterns of the natives in Brazil, constituting a critical scenario in the emergence of cardiovascular risk factors through the presence of excess weight, sedentary lifestyle, hypertension, diabetes, dyslipidaemias, factors directly related to these characteristics, and changes in the food patterns of these Indians, which was confirmed in the present study. Additionally, the scarcity of published studies on food consumption among indigenous populations of Brazil or specific ethnic groups.

The transition of food patterns can be related to changes in choice and the ability to obtain food that occurred in this ethnic group, due to the process of expansion of agricultural frontiers, causing individuals within this group to lose their territories and migrate to urban areas without the possibility of growing food or raising animals. In support of this hypothesis, we found a higher prevalence of hypertension among indigenous people living in urban areas, who consume less food through collecting and fishing than do non-hypertensive individuals. This finding is corroborated when the origin of the food is evaluated by urban and rural areas, since there was a significant difference (p ≤ 0.05) between the groups of indigenous people in rural areas compared to those in urban areas regarding food and/or animal husbandry at home, the collection of farmed and/or home-grown animals, food purchased by hunting and/or fishing, and the receipt of basic food baskets. Therefore, the results indicate that the indigenous people of rural areas had a higher availability of natural resources for hunting and fishing activities with the possibility of acquiring food than in the urban areas where the Mura Indians live; these areas present more difficulties in accessing food and a lower availability of natural resources required to purchase food, such as areas available for planting; a direct source of in natura foods (vegetables, fruits and carbohydrates) from the field; forest areas for the practice of hunting; and material resources available for fishing. Such as canoes, oars and outboard motors. Additionally, the urbanization of the city of Autazes may have a direct influence on the availability and abundance of game animals, such as tapirs, pacas, armadillos, and catitus, with effects on the availability of fish in the rivers of the region.

In this sense, an ethnographic study conducted from 2013 to 2014 on the changes in the eating habits of the Akwen Xerente Indians of the villages Porteira and Funil in the state of Tocantins, indicated that cultural changes, changes in livelihoods with the decrease in the insertion in the labour market, the provision of social benefits and the addition of technological resources through the distribution of the electric network in the villages made possible direct changes in the alimentary habits of these Indians. Evidence of these changes in dietary habits was identified by the presence of various types of industrialized food available for commercialization in Akwen Xerente indigenous villages, such as bottled and artificial juices, instant noodles, soybean oil, margarine, packaged biscuits, and powdered chocolate [45].

There were no differences in the consumption of alcohol between hypertensive and non-hypertensive Indians. However, there was a high consumption prevalence (40.2%), which was more than double that in the Brazilian population in 2013 (16.4%) [37]. In Brazil, the marketing of alcoholic beverages on indigenous lands is prohibited. However, fermented beverages made from tubers, which are typical of indigenous cultures such as the Caxiri, Aluah and Tarubá, have been replaced by distilled beverages as a consequence of the expropriation of lands, the reduction and exploitation of indigenous territories, self-sustainability and migration to urbanized areas, where the access to and marketing of alcoholic beverages is poorly controlled. In this context, alcoholism has been linked to cases of homicide, suicide, violence among groups, incest, sexual abuse and rape, and an increase in the mortality rate within indigenous areas in different Brazilian states [22].

Other important cardiovascular risk factors observed in this population were diabetes mellitus and glucose intolerance. Decreased glucose tolerance or pre-diabetic state refers to subjects who present glycemia from 140 to 199 mg / dL after 2 h in the oral glucose tolerance test (OGTT) [12].

The occurrence of diabetes mellitus and glucose intolerance contributes to vascular injury and affects renal function, favouring blood pressure elevation. In addition, the personal history of diabetes mellitus, independent of other variables, classifies the individual as having a high cardiovascular risk. Among the Mura Indians studied, 5.1% reported a history of diabetes mellitus, and 3.0% presented plasma glucose levels compatible with diabetes. These findings were higher than the prevalence observed among indigenous Guaraní (1.5%), Tupinkim (4.2%) [20] and Khisêdjê (3.8%) Indians [19] and were slightly below that observed among indigenous people in the village of Jaguapiru (5.8%) [10]. Although the prevalence of diabetes among the Mura Indians was lower than that observed in the non-indigenous population, this rate was higher than those pertaining to other ethnicities. Thus, this finding reflects the incorporation of new habits and food products, such as soft drinks, sweet drinks, ice cream, and sweets, and the high frequency of sugar utilization in food preparation.

In indigenous daily life, smoking may be related to beliefs or rituals. The prevalence of smoking among the Mura Indians was 20.4%, with a lower rate of smoking among hypertensive Indians. Among the Kaiowá, Guaraní and Terena Indians, the prevalence of smoking was 19.0% [14], while that among the Tupinikim Indians (60.4%) [20] and Kaingang and Guaraní Indians (44.0%) was much higher [17]. Although cigarette smoking among indigenous people is strongly influenced by historical and cultural manifestations, the high prevalence observed is of concern, since it is related to cardiovascular events and lesions of target organs, in addition to other non-transmissible chronic diseases. The lower prevalence of smoking observed in hypertensive Indians could be related to changes in habits and lifestyle after the diagnosis of the disease. However, in this population, the absence of ex-smokers was observed, which is not consistent with this hypothesis. Hypertension is a chronic multifactor non-communicable disease, and in the study population, other risk factors, such as measures associated with nutritional assessment and elevated triglyceride and cholesterol levels, were more prevalent in hypertensive patients

In conclusion, the Mura Indians presented a high prevalence of cardiovascular risk factors, especially hypertension. The findings show an epidemiological and nutritional transition, which may allow for the increase in risk factors for chronic non-communicable diseases. In light of the findings, it is important to establish health policies with a focus on the prevention of cardiovascular risk factors and health education strategies for adopting healthier habits and lifestyles. Thus, the multidisciplinary work of the health team regarding attention to the natives is necessary to meet the actual needs of these populations and to modify the profile of morbimortality resulting from the epidemiological transition that they experience.