Abstract
This study examines cohorts of Yanomami and Yekwana individuals in Venezuela to assess how age affects blood pressure rise over time in isolated communities without Western exposure.
A dogma of cardiology is that blood pressure (BP) increases with age.1,2 Yet studies of non-Westernized adults from isolated hunter-gatherer peoples have found little evidence of an age-associated rise in BP.3 To date, no studies have recorded BP in children of isolated communities and examined the age-BP association over the entire lifespan, and no studies have compared age-BP association in geographically colocated communities with different levels of Westernization.
In this study, we examine the age-BP association in 2 Amerindian communities, the Yanomami and the Yekwana, from a remote area of the Venezuelan rainforest inaccessible by land. The Yanomami community is made up of hunter-gatherer-gardeners who are among the least acculturated peoples in the world, and to our knowledge, their adults have the lowest known BP measurements.3,4 The Yekwana people live near the Yanomami people, but have been affected by missions and an airstrip for small-engine planes,5 which has allowed for delivery of medicine and aspects of Western lifestyle, including intermittent exposure to processed foods and salt. We hypothesized that BP does not rise with age across the lifespan in Yanomami individuals and the age-BP slope is steeper in Yekwana individuals than Yanomami individuals.
Methods
The Venezuelan Institute for Scientific Research approved this study. Informed consent was obtained, starting with obtaining the approval of the village chief and council. Volunteer participants were informed about the study using an interpreter if they did not understand Spanish, and adults consented individually to their participation by either signing or fingerprint-stamping the informed consent, as approved by the institutional review board. In the case of children (<18 years), parents consented as noted, and children provided assent.
Study investigators, certified in auscultatory BP measurement at Johns Hopkins University, measured sitting BP according to standard protocols. Analysis of covariance was performed to compare age-BP intercepts and slopes.
All P values less than .05 were considered significant. Data collection occurred from October 2015 to February 2016, and data analysis from March 2017 to September 2018. Stata version 15.1 (StataCorp) was used for data analysis.
Results
Our sample included 72 Yanomami participants and 83 Yekwana participants aged 1 to 60 years. The 2 groups were not significantly different in mean age, sex distribution, or height; a subsample differed in weight and body mass index (calculated as weight in kilograms divided by height in meters squared) (mean [SD] weight: Yanomami individuals, 41.4 [13.1] kg; Yekwana individuals, 48.4 [14.4] kg; mean [SD] body mass index: Yanomami individuals, 21.2 [3.9]; Yekwana individuals, 23.4 [4.4]; Table). Over all ages combined, Yanomami participants had lower systolic BP (SBP) (mean [SD]: Yanomami individuals, 95.4 [8.7] mm Hg; Yekwana individuals, 104.0 [10.6] mm Hg; P < .001) and diastolic BP (DBP) (mean [SD]: Yanomami individuals, 62.9 [8.5] mm Hg; Yekwana individuals, 66.1 [9.5] mm Hg; P = .03).
Table. Characteristics of Yanomami and Yekwana Participants.
| Characteristic | Yanomami | Yekwana |
|---|---|---|
| No. of participantsa | 72 | 83 |
| Age, mean (SD), y | 22.4 (15.1) | 22.2 (13.4) |
| Sex, No. (%) | ||
| Male | 39 (54) | 33 (40) |
| Female | 33 (46) | 50 (60) |
| Height, mean (SD), cm | 138.0 (13.0) | 141.7 (12.9) |
| Weight, mean (SD), kg | 41.4 (13.1) | 48.4 (14.4) |
| BMI, mean (SD) | 21.2 (3.9) | 23.4 (4.4) |
| Sitting blood pressure, mean (SD), mm Hg | ||
| Systolic | 95.4 (8.7) | 104.0 (10.6) |
| Diastolic | 62.9 (8.5) | 66.1 (9.5) |
Abbreviation: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared).
All statistics are from the full sample; however, only 48 Yanomami individuals and 56 Yekwana individuals had height data, only 36 Yanomami individuals and 49 Yekwana individuals had weight data, and therefore only 36 Yanomami individuals and 49 Yekwana individuals had BMI values calculated.
Importantly, while there was no difference between Yanomami and Yekwana in the age-SBP intercept, the age-SBP slope was significantly steeper (0.26 [95% CI, 0.04-0.47] mm Hg per year) for Yekwana individuals than Yanomami individuals (P= .02 for the interaction). In Yanomami individuals, the mean (SE) age-SBP slope was 0.00 (0.07) mm Hg per year (P = .98 for the difference from 0; Figure), whereas in Yekwana individuals, the mean (SE) age-SBP slope was 0.25 (0.08) mm Hg per year (P = .003 for the difference from 0). Findings for the association between age and DBP were similar (mean [SE] age-DBP slope: Yanomami individuals, −0.02 [0.07] mm Hg; P = .77; Yekwana individuals, 0.18 [0.08] mm Hg; P = .02; Figure). Thus, although the Yanomami and Yekwana groups started out with similar BP, between-group differences in BP increased with age. For example, at age 10 years, mean SBP was 5.8 mm Hg higher in Yekwana individuals than Yanomami individuals, rising to a 15.9–mm Hg difference by age 50 years. Moreover, our data indicate these divergent BP trends may already start in childhood, because there was a steeper age-SBP slope in Yekwana individuals compared with Yanomami individuals aged 1 to 20 years (mean [SE] difference, 0.98 [0.39] mm Hg per year; P = .01).
Figure. Scatter Plots of Sitting Systolic and Diastolic Blood Pressure Levels by Age in Yekwana and Yanomami Individuals Aged 1 to 60 Years.
Discussion
While the Yanomami have fascinated hypertension researchers, their isolation combined with restricted government access has prevented substantive research in this population. To our knowledge, this is the first study to examine the age-BP association over the Yanomami lifespan, including in childhood. Our finding of no age-associated rise in Yanomami children and adults is consistent with adult-only Yanomami data.3 Further, in those aged 1 to 20 years, Yekwana had a steeper age-SBP slope, indicating BP differences may emerge in childhood. To put our findings into context, in the United States, SBP increases by approximately 1.5 mm Hg per year among girls,1 approximately 1.9 mm Hg per year among boys,1 and approximately 0.6 mm Hg per year in adults.2
Conclusions
Although our study is cross-sectional and limited by small sample size, it adds to findings in Yanomami adults3 showing that the rise in BP with age may not be natural but rather a consequence of unnatural Western exposures. Furthermore, the age-associated BP rise in the more Westernized Yekwana community began in childhood, highlighting the potential for lifestyle interventions in children to prevent elevated BP. This study of BP over the lifespan of 2 relatively isolated Amerindian communities from the Venezuelan rainforest helps to disentangle the effects of aging vs modern lifestyle on BP, supporting primordial prevention efforts (ie, those directed at avoiding the development of risk factors) to eliminate elevated BP.
References
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