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Article Archive: Vadez V

Developmental changes in the relationship between leptin and adiposity among Tsimané children and adolescents
Huanca T, Kuzawa CW, Leonard WR, McDade TW, Reyes-García VE, Sharrock KC, Tanner S, Vadez V
Am J Hum Biol 20(4):392-8
1 July 2008
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Leptin is thought to signal energy stores, thus helping the body balance energy intake and expenditure. However, the strong relationship between leptin and adiposity in populations with adequate nutrition or common obesity is not universal across ecologic contexts, and leptin often correlates only weakly, or not at all, with adiposity in populations of lean or marginally-nourished males. To clarify whether the relationship between adiposity and leptin changes during development, this study examines leptin and body fat among children and adolescents of lowland Bolivia. Anthropometric measures of body composition and dried blood spot samples were collected from 487 Tsimane' ranging from 2 to 15 years of age. Leptin was assayed using an enzyme immunoassay protocol validated for use with blood spot samples. In this population, leptin concentrations were among the lowest reported in a human population (mean +/- SD: 1.26 +/- 0.5 and 0.57 +/- 0.3 in females and males). In addition, the relationship between leptin and adiposity follows distinct developmental trajectories in males and females. In males, leptin is weakly correlated with most measures of body composition at all ages investigated. However, in females, the level of body fat and the strength of the correlation between body fat and leptin (a measure of its strength as a signal of energy stores) both increase markedly with age. These findings suggest a more important role of leptin as a signal of energy stores among females as they approach reproductive maturity, while raising questions about the function of this hormone in lean males.

Academic Articles by NU Faculty
Adiposity, Adolescent, Age Factors, Anthropometry, Body Mass Index, Bolivia/epidemiology, Child, Child, Energy Metabolism, Female, Humans, Leptin/metabolism, Male, Nutritional Status, Obesity/epidemiology, Obesity/metabolism, Obesity/physiopathology, Pilot Projects, Preschool
Does village inequality in modern income harm the psyche? Anger, fear, sadness, and alcohol consumption in a pre-industrial society.
Godoy RA, Huanca T, Leonard WR, McDade T, Reyes-García V, Tanner S, Vadez V
Soc Sci Med 63(2):359-72
1 July 2006
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Researchers have found a positive association between income inequality and poor individual health. To explain the link, researchers have hypothesized that income inequality erodes community social capital, which unleashes negative emotions, stress, and stress behaviors that hurt health. Few studies have tested the hypothesized path. Here we estimate the association between (a) village income inequality and social capital, and (b) three distinct negative emotions (anger, fear, sadness) and one stress behavior (alcohol consumption). We use four quarters of panel data (2002-2003) from 655 adults in 13 villages of a foraging-farming society in the Bolivian Amazon (Tsimane'). We found that: (1) village income inequality was associated with more negative emotions but with less alcohol consumption, (2) social capital always bore a negative association with outcomes, and (3) results held up after introducing many changes to the main model. We conclude that village income inequality probably affects negative emotions and stress behaviors through other paths besides social capital because we conditioned for social capital. One such path is an innate dislike of inequality, which might have pre-human origins. Our prior research with the Tsimane' suggests that village income inequality bore an insignificant association with individual health. Therefore, village income inequality probably affects negative emotions and stress behaviors before undermining health.

Academic Articles by NU Faculty
Adult, Alcohol Drinking/economics, Alcohol Drinking/epidemiology, Bolivia, Econometric, Emotions, Female, Humans, Income, Indians, Interpersonal Relations, Male, Models, Psychological/economics, Psychological/epidemiology, Rural Population, Social Support, South American, Stress, Stress
Ethnobotanical skills and clearance of tropical rain forest for agriculture: a case study in the lowlands of Bolivia
Huanca T, Leonard WR, McDade T, Reyes-García V, Tanner S, Vadez V
Ambio 36(5):406-8
1 July 2007
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Indigenous peoples are often considered potential allies in the conservation of biological diversity. Here we assess whether ethnobotanical skills of indigenous people contribute to a reduction in the clearance of tropical rain forest. We measured ethnobotanical skills of male household heads and area of rain forest cleared for agriculture among 128 households of Tsimane', a native Amazonian group in Bolivia. We used multivariate regressions to estimate the relation between ethnobotanical skills and area of rain forest cleared while controlling for schooling, health status, number of plots cleared, adults in household, and village of residency. We found that when the ethnobotanical skills of the male household head were doubled, the amount of tropical rain forest cleared per household was reduced by 25%. The association was stronger when the area of old-growth forest cleared was used as the dependent variable than when the area cleared from fallow forest was used as the dependent variable. People who use the forest for subsistence might place a higher value on standing forest than people who do not use it, and thus they may be more reluctant to cut down the forest.

Academic Articles by NU Faculty
Agriculture, Bolivia, Ethnobotany, Geography, Humans, Interviews as Topic, Rain, Trees, Tropical Climate
Evaluating indices of traditional ecological knowledge: a methodological contribution
Huanca T, Leonard WR, McDade T, Reyes-García V, Tanner S, Vadez V
Journal of ethnobiology and ethnomedicine 2:21
1 January 2006
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BACKGROUND: New quantitative methods to collect and analyze data have produced novel findings in ethnobiology. A common application of quantitative methods in ethnobiology is to assess the traditional ecological knowledge of individuals. Few studies have addressed reliability of indices of traditional ecological knowledge constructed with different quantitative methods.

METHODS: We assessed the associations among eight indices of traditional ecological knowledge from data collected from 650 native Amazonians. We computed Spearman correlations, Chronbach's alpha, and principal components factor analysis for the eight indices.

RESULTS: We found that indices derived from different raw data were weakly correlated (rho<0.5), whereas indices derived from the same raw data were highly correlated (rho>0.5; p < 0.001). We also found a relatively high internal consistency across data from the eight indices (Chronbach's alpha = 0.78). Last, results from a principal components factor analysis of the eight indices suggest that the eight indices were positively related, although the association was low when considering only the first factor.

CONCLUSION: A possible explanation for the relatively low correlation between indices derived from different raw data, but relatively high internal consistency of the eight indices is that the methods capture different aspects of an individual's traditional ecological knowledge. To develop a reliable measure of traditional ecological knowledge, researchers should collect raw data using a variety of methods and then generate an aggregated measure that contains data from the various components of traditional ecological knowledge. Failure to do this will hinder cross-cultural comparisons.

Academic Articles by NU Faculty
Adolescent, Adult, Attitudes, Bolivia, Cross-Cultural Comparison, Ecology/methods, Ecology/standards, Ethnobotany/methods, Female, Health Knowledge, Herbal Medicine, Humans, Indians, Male, Plant Extracts, Practice, Questionnaires, Research, South American, Statistics as Topic, Young Adult
Human capital, wealth, and nutrition in the Bolivian Amazon.
Bauchet J, Godoy R, Huanca T, Leonard WR, Reyes-García V, Vadez V
Economics and human biology 3(1):139-62
1 March 2005
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We analyze anthropometric variables of a society of forager-horticulturalists in the Bolivian Amazon (Tsimane') in 2001-2002. Community variables (e.g., inequality, social capital) explain little of the variance in anthropometric indices of nutritional status, but individual-level variables (schooling, wealth) are positively correlated with nutritional status. Dietary quality (foods high in animal proteins), access to foraging technology, and traditional knowledge of medicinal plants are related to better anthropometric indices.

Academic Articles by NU Faculty
Adolescent, Adult, Aged, Agriculture, Anthropometry, Body Weights and Measures/economics, Bolivia, Diet/economics, Female, Humans, Indians, Male, Middle Aged, Nutritional Status, Rural Population, Socioeconomic Factors, South American
Income inequality and adult nutritional status: anthropometric evidence from a pre-industrial society in the Bolivian Amazon
Apaza L, Byron E, Godoy R, Huanca T, Leonard WR, Pérez E, Reyes-García V, Vadez V, Wilkie D
Soc Sci Med 61(5):907-19
1 September 2005
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Evidence has been accumulated about the adverse effects of income inequality on individual health in industrial nations, but we know less about its effect in small-scale, pre-industrial rural societies. Income inequality should have modest effects on individual health. First, norms of sharing and reciprocity should reduce the adverse effects of income inequality on individual health. Second, with sharing and reciprocity, personal income will spill over to the rest of the community, attenuating the protective role of individual income on individual health found in industrial nations. We test these ideas with data from Tsimane' Amerindians, a foraging and farming society in the Bolivian Amazon. Subjects included 479 household heads (13+ years of age) from 58 villages. Dependent variables included anthropometric indices of short-run nutritional status (body-mass index (BMI), and age- and sex-standardized z-scores of mid-arm muscle area and skinfolds). Proxies for income included area deforested per person the previous year and earnings per person in the last 2 weeks. Village income inequality was measured with the Gini coefficient. Income inequality did not correlate with anthropometric indices, most likely because of negative indirect effects from the omission of social-capital variables, which would lower the estimated impact of income inequality on health. The link between BMI and income and between skinfolds and income resembled a U and an inverted U; income did not correlate with mid-arm muscle area. The use of an experimental research design might allow for better estimates of how income inequality affects social capital and individual health.

Academic Articles by NU Faculty
Adolescent, Adult, Anthropometry, Body Weights and Measures, Bolivia, Female, Humans, Indians, Male, Nutritional Status, Poverty, Rural Population, South American
Nutritional status and spousal empowerment among native Amazonians
Godoy RA, Leonard WR, McDade T, Patel A, Reyes-García V, Seyfried CF Jr, Tanner S, Vadez V
Soc Sci Med 63(6):1517-30
1 September 2006
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Researchers and development organizations have shown interest in individual empowerment because it presumably improves well-being. Estimates of empowerment's effects on well-being contain biases from the potential endogeneity of empowerment. Using data from a sexually egalitarian and highly autarkic society of foragers and horticulturalists in the Bolivian Amazon, the Tsimane', we overcome the problems that this poses by: (1) matching spouses' responses to the same questions about who makes decisions or who breaks ties in 10 domains to improve accuracy in measures of empowerment; and (2) using parental attributes of spouses as instrumental variables for spousal empowerment. Outcomes include two anthropometric indices of short-run nutritional status: body-mass index and age and sex-standardized z scores of mid-arm muscle area. The amount of empowerment of household heads did not affect their nutritional status or other indicators of their well-being, such as income, wealth, expenditures, happiness, social capital, or self-perceived health. It also did not affect the nutritional status of their offspring. Nor did it affect the difference in income, wealth, or monetary expenditures between spouses. The insubstantial effects persisted with other definitions of empowerment or types of regressions. We end with a discussion of why empowerment, despite its popularity in development discourse, has such tenuous links with objective indicators of well-being, and the implication of this finding for future studies of empowerment's effects.

Academic Articles by NU Faculty
Adult, Asian Continental Ancestry Group/statistics & numerical data, Basal Metabolism, Body Composition, Body Size, Calorimetry, Deuterium Oxide/diagnostic use, Energy Metabolism, Female, Humans, Indirect, Life Style, Male, Middle Aged, Motor Activity, Physical Exertion, Sex Factors, Siberia
Physical stature of adult Tsimane' Amerindians, Bolivian Amazon in the 20th century
Godoy RA, Goodman E, Huanca T, Leonard WR, McDade T, Reyes-García V, Tanner S, Vadez V
Economics and human biology 4(2):184-205
1 June 2006
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We examine the association between exposure to the market and Western society on the height of adult Tsimane', a foraging-farming society in the Bolivian Amazon. As with other contemporary native peoples, we find little evidence of a significant secular change in height during 1920-1980. Female height bore a positive association with own schooling and fluency in spoken Spanish and with maternal modern human capital (schooling, writing ability, and fluency in spoken Spanish), but male heights bore no association with parental height or with modern human capital. The absence of a secular change likely reflects the persistence of traditional forms of social organization and production that protect health.

Academic Articles by NU Faculty
Adult, Anthropometry/methods, Body Height/physiology, Bolivia, Female, Humans, Male, Nutritional Status, Population Groups, Western World
Predictors of C-reactive protein in Tsimane' 2 to 15 year-olds in lowland Bolivia
Burhop J, Godoy RA, Huanca T, Leonard WR, McDade TW, Reyes-García V, Vadez V
Am J Phys Anthropol 128(4):906-13
1 December 2005
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Infectious disease is a major global determinant of child morbidity and mortality, and energetic investment in immune defenses (even in the absence of overt disease) is an important life-history variable, with implications for human growth and development. This study uses a biomarker of immune activation (C-reactive protein) to investigate an important aspect of child health among the Tsimane', a relatively isolated Amerindian population in lowland Bolivia. Our objectives are twofold: 1) to describe the distribution of CRP by age and gender in a cross-sectional sample of 536 2-15-year-olds; and 2) to explore multiple measures of pathogen exposure, economic resources, and acculturation as predictors of increased CRP. The median blood-spot CRP concentration was 0.73 mg/l, with 12.9% of the sample having concentrations greater than 5 mg/L, indicating a relatively high degree of immune activation in this population. Age was the strongest predictor of CRP, with the highest concentrations found among younger individuals. Increased CRP was also associated with higher pathogen exposure, lower household economic resources, and increased maternal education and literacy. The measurement of CRP offers a direct, objective indicator of immune activation, and provides insights into a potentially important pathway through which environmental quality may shape child growth and health.