Article Archive: Adolescent

J Physiol Anthropol 26(2):241-6
1 March 2007

C-reactive protein (CRP) is an inflammatory marker, which at low-level elevations is associated with increased cardiovascular risk. Although CRP has been extensively investigated in North American and European settings, few studies have measured CRP among non-Western groups. The present study used dried whole blood spot samples to examine high-sensitivity CRP concentrations among the Yakut (Sakha) of Siberia (85 females, 56 males; 18-58 years old). Our goals were: (1) to compare Yakut CRP concentrations with other populations; (2) to investigate sex differences; and (3) to explore anthropometric correlates of CRP. Results indicate that serum equivalent CRP concentrations are similar to those from industrializing nations, lower than US and European values, and greater than Japanese concentrations. Yakut men and women display similar CRP concentrations; however, CRP was significantly higher among men after adjustment for body fat, age, and smoking. Positive associations were documented between CRP and BMI, body fat, and central adiposity.

Annals of human biology 32(4):469-86
1 July 2005


AIM: The study analysed variability in physical stature, weight, and body mass index (BMI) in the USA during 1971-2002.

SUBJECTS: Subjects were non-Hispanic Blacks and Whites, 2-74 years of age from the National Health and Nutrition Examination Surveys (NHANES I-III and 1999-2002).

METHODS: The coefficient of variation and the standard deviation of the logarithm of stature, weight, and BMI were used to assess anthropometric variability for groups defined by age, race, sex, income, and survey year. Weighted ordinary least squares regressions were used to estimate the effect of socio-economic variables on anthropometric variability.

RESULTS: (a) The relation between age and variability in weight or BMI resembles an inverted U, (b) men have lower variability in BMI than women, (c) Blacks and the poor have greater variability in weight and BMI than Whites or than the non-poor, and (d) variability in anthropometric indices increased during 1971-2002. Results were robust to the measure of variability used and to the use of the mean and mean square of the anthropometric indicators as explanatory variables.

CONCLUSION: Since anthropometric indices correlate reliably with canonical indicators of well-being (e.g. income), growing variability in anthropometric indices, particularly among the Blacks and the poor, signals growing inequality in quality of life--a worrisome trend.

American journal of human biology 2005 Mar-Apr; 17(2):155-72
1 March 2005

Human indigenous circumpolar populations have elevated basal metabolic rates (BMRs) relative to predicted values; this metabolic elevation has been postulated to be a physiological adaptation to chronic and severe cold stress. The present study examines BMR in the Yakut, an indigenous high-latitude population from the Sakha Republic of Russia to determine (1) whether the Yakut show evidence of an elevated BMR, (2) if the Yakut display evidence of age-related changes in BMR, and (3) whether lifestyle differences influence BMR. BMR was measured during the late summer in 75 women and 50 men (ages 18-56 years) from the Siberian village of Berdygestiakh. Measured BMR (+/- SEM) of the entire sample was significantly elevated (+6.5%) compared to predictions based on body mass (6,623.7 +/- 94.9 vs. 6,218.2 +/- 84.7 kJ/day; P < 0.001). Additionally, measured BMR for the entire sample was significantly higher than predictions based on fat-free mass (+20.8%) and surface area (+8.9%). Males and females both showed significant elevations relative to all three standards. The elevated BMR of the Yakut does not appear to be attributable to extreme levels of protein, since the Yakut consume a mixed diet with a substantial proportion of carbohydrates. No significant age-related changes in BMR were found when controlled for body composition. No significant relationship was found between lifestyle variables and BMR, suggesting the possibility of a genetic or developmental mechanism. This study provides additional evidence of metabolic elevation in indigenous circumpolar groups and has important implications for estimating the nutritional requirements of these populations.

Am J Hum Biol 20(4):392-8
1 July 2008

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.

Journal of ethnobiology and ethnomedicine 2:21
1 January 2006

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.

Economics and human biology 3(1):139-62
1 March 2005

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.

Soc Sci Med 61(5):907-19
1 September 2005

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.

Am J Phys Anthropol 128(4):906-13
1 December 2005

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.

Ann Hum Biol 35(3):276-93.
1 May 2008

BACKGROUND: Global climate change and recent studies on early-life origins of well-being suggest that climate events early in life might affect health later in life.

AIM: The study tested hypotheses about the association between the level and variability of rain and temperature early in life on the height of children and adolescents in a foraging-farming society of native Amazonians in Bolivia (Tsimane'). SUBJECT AND METhods: Measurements were taken for 525 children aged 2-12 and 218 adolescents aged 13-23 in 13 villages in 2005. Log of standing height was regressed on mean annual level and mean intra-annual monthly coefficient of variation (CV) of rain and mean annual level of temperature during gestation, birth year, and ages 2-4. Controls include age, quinquennium and season of birth, parent's attributes, and dummy variables for surveyors and villages.

RESULTS: Climate variables were only related with the height of boys age 2-12. The level and CV of rain during birth year and the CV of rain and level of temperature during ages 2-4 were associated with taller stature. There were no secular changes in temperature (1973-2005) or rain (1943-2005).

CONCLUSION: The height of young females and males is well protected from climate events, but protection works less well for boys ages 2-12.

Am J Hum Biol 21(5):664-70
1 September 2009

Over the last 20 years, obesity and associated metabolic diseases have emerged as major global health problems. Among urbanizing populations of developing regions of the world, childhood undernutrition often coexists with adult overnutrition, a phenomenon known as the "dual nutritional burden". A recent work (Frisancho 2003: Am J Hum Biol 15:522-532) suggests that linear growth stunting in early childhood may contribute to adult obesity by reducing the body's ability to oxidize fat. We test central aspects of this model drawing on data from 112 adult Buryat herders (53 males; 59 females) from Southern Siberia. The results are consistent with the predictions of the model, but only for women. Shorter Buryat women (height-for-age Z-scores < or = -1) have significantly lower fasting fat oxidation levels compared to their taller counterparts. Shorter women are also significantly heavier and fatter, and have higher serum lipid levels. Among all Buryat women, reduced fat oxidation is significantly correlated with percent body fatness, serum triglyceride levels, and serum leptin levels, after controlling for relevant covariates. Additionally, Buryat women with high dietary fat intakes and low fat oxidation are significantly fatter and have higher lipid and leptin levels than those with low fat intakes and high fat oxidation. These results suggest that developmental changes in fat oxidation may play a role in the origins of obesity among populations with high rates of linear growth stunting. Further longitudinal research is necessary to elucidate the pathways through which early-life undernutrition may increase risks for adulthood obesity and cardiovascular disease.

Journal of physiological anthropology 25(1):75-84
1 January 2006

Once considered a disease of affluence and confined to industrialized nations, obesity is currently emerging as a major health concern in nearly every country in the world. Available data suggest that the prevalence rate of obesity has reached unprecedented levels in most developing countries, and is increasing at a rate that far outpaces that of developed nations. This increase in obesity has also been documented among North American circumpolar populations and is associated with lifestyle changes related to economic development. While obesity has not been well studied among indigenous Siberians, recent anthropological studies indicate that obesity and its associated comorbidities are important health problems.The present study examines recent adult body composition data from four indigenous Siberian populations (Evenki, Ket, Buriat, and Yakut) with two main objectives: 1) to determine the prevalence of overweight and obesity among these groups, and 2) to assess the influence of lifestyle and socioeconomic factors on the development of excess body fat. The results of this study indicate that obesity has emerged as an important health issue among indigenous Siberians, and especially for women, whose obesity rates are considerably higher than those of men (12% vs. 7%). The present study investigated the association between lifestyle and body composition among the Yakut, and documented substantial sex differences in lifestyle correlates of obesity. Yakut men with higher incomes and who owned more luxury consumer goods were more likely to have excess body fat while, among Yakut women, affluence was not strongly associated with overweight and obesity.

Am J Phys Anthropol 137(2):145-55
1 October 2008

Hypertension is an important global health issue and is currently increasing at a rapid pace in most industrializing nations. Although a number of risk factors have been linked with the development of hypertension, including obesity, high dietary sodium, and chronic psychosocial stress, these factors cannot fully explain the variation in blood pressure and hypertension rates that occurs within and between populations. The present study uses data collected on adults from three indigenous Siberian populations (Evenki, Buryat, and Yakut [Sakha]) to test the hypothesis of Luke et al. (Hypertension 43 (2004) 555-560) that basal metabolic rate (BMR) and blood pressure are positively associated independent of body size. When adjusted for body size and composition, as well as potentially confounding variables such as age, smoking status, ethnicity, and degree of urbanization, BMR was positively correlated with systolic blood pressure (SBP; P < 0.01) and pulse pressure (PP; P < 0.01); BMR showed a trend with diastolic blood pressure (DBP; P = 0.08). Thus, higher BMR is associated with higher SBP and PP; this is opposite the well-documented inverse relationship between physical activity and blood pressure. If the influence of BMR on blood pressure is confirmed, the systematically elevated BMRs of indigenous Siberians may help explain the relatively high blood pressures and hypertension rates documented among native Siberians in the post-Soviet period. These findings underscore the importance of considering the influence of biological adaptation to regional environmental conditions in structuring health changes associated with economic development and lifestyle change.

Econ Hum Biol 8(1):88-99
1 March 2010

Among adults of industrial nations, growth stunting (<-2 SD height Z score) is associated with worse indicators of adult well-being (e.g., income). Does adult stunting also inflict private costs in traditional societies? Adult stunting penalties or height premiums might only emerge when traditional societies modernize. Here we estimate the association between adult stunting and indicators of adult well-being using data from a panel study in progress among the Tsimane', a foraging-farming society of native Amazonians in Bolivia. Subjects included 248 women and 255 men >or=age 22 measured annually during 5 consecutive years (2002-2006). Nine outcomes (wealth, monetary income, illness, access to credit, mirth, schooling, math skills, plant knowledge, forest clearance) were regressed separately against a stunting dummy variable and a wide range of control variables. We found no significant association between any of the indicators of own well-being and adult stunting. Additional analysis showed that stunting bore an association only with poorer mid-arm muscle area. Height premiums and stunting penalties, though evident and marked in modern societies, might not be common in all traditional societies.