Blood Pressure Studies Among Amazonian Native Populations: a Review from an Epidemiological Perspective
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Sm. Sci. Med. Vol. 31, No. 5, pp. 593601, 1990 0277-9536190 53.00 + 0.00 Printed in Great Britain. All rights reserved Copyright Q 1990Pergamon Press plc BLOOD PRESSURE STUDIES AMONG AMAZONIAN NATIVE POPULATIONS: A REVIEW FROM AN EPIDEMIOLOGICAL PERSPECTIVE MILLICENT FLEMING-MORAN’ and CARLOS E. A. COIMBRA JR’ ‘Center on Aging/SPEA, Indiana University, Indianapolis, IN 46201, U.S.A. and *Department of Epidemiologia. Escola National de Saude Publica, Fiocruz, Rio de Janeiro, Brazil Abstract-Nine publications are reviewed concerning blood pressure (BP) levels among Amerindian tribes of the Amazon Basin. The lifestyle of these lowland peoples includes most known protective factors against hypertension, and relative isolation from Western society. The latter, however, is rapidly changing. Sampling, data, and analysis problems make current blood pressure data difficult to interpret, and provide a questionable baseline from which to document pressure change during rapid culture change for these groups. Ethnographic and epidemiological perspectives are offered for future blood pressure and health studies among native Amazonians. Key words-blood pressure, hypertension, Amerindian, Amazon, cultural change, epidemiology, blood pressure measurement, male/female differences in diet INTRODUCIION relative social homogeneity among tribal members [7, 12, 131. Numerous researchers have now compared ‘tradi- However, even the most isolated Amazonian tional’ societies with industrial nations, and docu- groups face highways, mining, agricultural coloniz- mented differences in age/sex trends in mean blood ation and other development projects in the pressure levels, or differential rates of hypertension Basin, particularly since the 1970s [16, 18, 191. These prevalence [ 11. These studies often contradict Western societies now represent a continuum of increasing experience, where blood pressure increases with age, contact and integration with the larger Western and mean pressure levels for adult males normally society [20,21]. Most now live in large territorial exceed that of adult females [2,3]. Similar trends in reservations. Increased access to Western medical age/sex increases in blood pressure occasionally have care has been a part of this process, including been noted for traditional societies undergoing social health surveillance and blood pressure measurement change, or in subjects who migrate from pre- [e.g. 9, 10, 12, 19. Biomedical researchers, health industrial settings to modem, urban societies [4-6]. officials and social scientists continue to collaborate These patterns have fostered on-going epidemio- in the difficult work of recording changes in logical debate. Does blood pressure necessarily Amerindian health status during this period [e.g. increase with advancing age? Are there always signifi- 9, 10, 13, 16,22-251. cant differences in mean pressure levels between the There have been numerous suggestions of an asso- sexes when age and weight factors are considered? ciation between greater mean blood pressure levels Finally, is there a consistent relationship between and the increase in social complexity of a population socio-cultural disruption in a society, and long- [3-7,26-291. As a formally isolated and homoge- term blood pressure alteration for its individual neous group becomes acculturated, or its members members? migrate to a larger, more complex society, greater Certain reviewers do not attempt comparisons of social stratification and specializaton occur. This blood pressure data from nonindustrial groups due to poses several cultural, physical and psychological methodological problems [e.g. 7,8], and the diversity challenges and changes for the group’s members. of historical experiences of each traditional society as The terms ‘acculturation’ and ‘culture change’ have it encounters another culture [l]. Unfortunately this been used somewhat interchangably in the social- is also true for research among the native peoples of medicine literature, implying certain assumptions the Amazon Basin, even though studied groups are have been made [30]. Most common is the notion isolated and small, and much of the research has been that the ‘pre-contact’ or ‘pre-migrational’ society conducted within the last 15 yr [7]. is relatively homogenous, its cultural values are Amerindian populations of the Amazon Basin unanimously accepted, and given its social integra- offer an opportunity to study a way of life which tion, the society is considered to be relatively ‘stress- incorporates most current maxims for preventing and free’ [30]. Post-contact acculturation, whether controlling hypertension. These include a regular proceeding to complete social assimilation, or new physical exercise, low sodium/high potassium diets cultural configurations, conversely, is taken to imply [9-111, low prevalence of obesity or diabetes extended social disintegration, economic change and [9, IO, 12-151, moderate use of low-alcohol or psychosocial distress. While social scientists today caffinated beverages in traditional diets [17] and would question such a static and undifferentiated 593 594 MILLKENT FLEMING-MORANand CARLOS E. A. COIMBU JR view of Amerindian societies, the general hypothesis We sampled only 124 of the 800 of the estimated popu- of Western-contact/social disintegration may be lation and the studied groups, the Kalapalo and the generally applicable to lowland groups of South Kamaiura, are those with which the researchers have had America. the longest contact.. other, more isolated groups will be studied . in the future (translation by authors). It is difficult, however, to test ‘acculturation’ as a construct in models of health status or disease prevalence. Tangible criteria for these socio-economic It must be recognized that ‘accessible’ villages may changes are needed, such that individual (versus not be representative of the total population. These group) differences in process of cultural change, and sites are more likely to include individuals who are presumably health risk, can be discerned. As one more dependent on wages, medical or other services, example, certain data suggest that process of cultural or who participate in governmental or missionary change affects social roles and health status of the two goals to ‘pacify’ the Indian groups, than are persons sexes differentially, and is associated with different from more isolated villages. health effects for members of various age cohorts Sampling and participation bias represent two of [7,26-28,301. the most severe problems in both the collection This review outlines the methodological hazards and interpretation of health data from Amerindian in this much needed anthropological and epidemio- societies. Although most authors state that measure- logical research on covariates of blood pressure, ments were attempted ‘. in all inhabitants’ [e.g. 91, as seen in previously published data for Amazonian age/sex pyramids for these studies indicate certain Amerindians. Sample selection, blood pressure and age groups, particularly males aged 2540 are strik- other data collection, data analysis and reporting, ingly underrepresented, even for a nonindustrial and research design will each be addressed. Ethno- population structure. Neel and co-workers, for graphic examples will illustrate common field con- example, provide useful age/sex ratios comparing ditions, and highlight specific variables which require their Xavante subjects, the Kaingang Amerindians of careful evaluation, if the mechanisms underlying southern Brazil, and the general 1950 Brazilian blood pressure response to cultural change are to be national census [12, p. 921. Taken together with the understood. Thus, the relative impact of modified sample sizes for the blood pressure data, the reader dietary and health habits, obesity, access to medical may deduce that 27% of Xavante under the age care and tangible cultural changes may be assessed of 15 were included in the study sample, as were for their independent (or interactive) effects on blood about 40% of the adults. As blood pressure data pressure level. were only a secondary objective of a larger genetic study, selection criteria for the blood pressure sub- SAMPLING PROCEDURES jects are not specified. However, as the representa- tiveness of the blood pressure data cannot be . (A)pproximately 12-15,000 Yanomamo are distributed evaluated, the reader can only speculate about ‘aver- among some 150 villages in an area of approximately age’ Xavante blood pressure levels, or comparisons 100,000. square miles. At present there are some 16 small with other Amerindian populations. The Xavante missions. as well as government health stations. for the most part located on navigable rivers. (How- study is but one of several which presents this ever,). there are probably villages yet to be visited by problem. non-indian[s]. The selected subjects consisted of all available Oliver and colleagues note that “. several inhabitants of sixteen. villages. In a few instances several wanomamo] . were absent on a hunting trip.. ” Indians were absent . on a hunting trip.. Selection of [9]; a common feature of Amerindian life. Groups villages was determined by a cross-section of widely dis- may also leave the village for gardening or collect- persed living sites . , as remote as possible, but still ing tasks, and women become inaccessible due to accessible by small plane or boat. Blood pressures ritual isolation during their menstrual periods, or were.. performed on 506 Indians during the expeditions