Secular trends in growth in the high-altitude district of Nuñoa, Peru 1964-2015

Pearl Memorial Lecture. Humans at the extremes: Exploring human adaptation to ecological and social stressors

The field of human biology has long explored how human populations have adapted to extreme environmental circumstances. Yet, it has become increasingly clear that conditions of social stress, poverty, and lifestyle change play equally important roles in shaping human biological variation and health. In this paper, I provide a brief background on the foundational human adaptability research of the International Biological Programme (IBP) from the 1960s, highlighting how its successes and critiques have shaped current research directions in the field. I then discuss and reflect on my own field research that has examined the influence of both environmental and social stresses on human populations living in different ecosystems: the Peruvian Andes, the Siberian arctic, and the Bolivian rainforest. Finally, I consider how the papers in this special issue advance our understanding of human adaptability to extreme conditions and offer directions for future research. Drawing on our field's distinctive evolutionary and biocultural perspectives, human biologists are uniquely positioned to examine how the interplay between social and ecological domains influences the human condition.

Human biology and the study of precarity: How the intersection of uncertainty and inequality is taking us to new extremes

Inequality represents an extreme environment to which humans must respond. One phenomenon that contributes to this growing extreme is precarity or the intersection of uncertainty and some form of inequality. While precarity has an important intellectual history in the fields of sociology and sociocultural anthropology, it has not been well studied in the field of human biology. Rather human biologists have engaged with the study of closely related concepts such as uncertainty and resource insecurity. In this article, we propose that human biology take on the study of precarity as a novel way of investigating inequality. We first provide a brief intellectual history of precarity which is followed by a review of research on uncertainty and resource security in human biology which, while not exhaustive, illustrates some key gaps that precarity may aid us in addressing. We then review some of the pathways through which precarity comes to affect human biology and health and some of the evidence for why the unpredictable nature of precarity may make it a unique physiological stress. A case study based on research in Nuñoa, Peru provides an important example of how precarity can elucidate the influences of health in an extreme setting, albeit with insights that apply more broadly. We conclude that precarity holds important potential for the study of human biology, including helping us more effectively operationalize and study uncertainty, encouraging us to explore the predictability of resources and stressors, and reminding us to think about the intersectional nature of stressors.

Childhood growth and education migration among ethnic Tibetan children from Nepal

BACKGROUND

Ethnographic work among high altitude populations has shown that children are highly mobile-the most recent expression of this is the educational migration of children born at high altitude to boarding schools at lower altitudes. The impact of these patterns of migration on size for age are unknown.

AIM

We investigated the association between growth in weight and height and educational migration in ethnic Tibetan children living in and out of their natal communities.

SUBJECTS AND METHODS

Five hundred and fifty eight children ages three to sixteen from the Nubri Valley, Nepal participated in this study. Three hundred children were living in natal villages and 258 were attending boarding schools in Kathmandu. Height, weight, and skinfold thicknesses were collected and matched to demographic data from the community.

RESULTS

There was no association between altitude of family residence and size for age z-scores. Males had lower z-scores than females; z-scores for both groups declined with age. Differences in size for age among children in boarding schools were associated with two factors: sex and type of boarding school (individual sponsor or group funded). Individuals attending individually sponsored schools had greater size for age compared to children in group funded schools or in their natal villages; younger children in collectively funded schools were smaller than village peers.

CONCLUSIONS

Despite popular perceptions, educational outmigration in Himalayan communities may not be associated with improved child growth outcomes and investment in community level schools may be a practical solution for improving child growth and physical and mental health.

Secular Trends in Physical Fitness of Peruvian Children Living at High-Altitude

The physical fitness of children is an important marker of health, and monitoring its temporal changes provides important information for developing interventions. We aimed to: (1) describe secular trends in physical fitness across age, within each sex, in Peruvian schoolchildren; and (2) verify if these trends are also present when adjusted for changes in height and weight. We sampled 1590 children (707 in 2009; 883 in 2019), aged 6-11 years. Physical fitness was assessed with four tests from the EUROFIT battery. ANOVA and ANCOVA statistical models were used. Results showed that with increasing age, girls and boys were significantly stronger in all PF tests, except for the case of flexibility in girls. In 2019, girls were stronger (handgrip) and more flexible than in 2009; but lower values were evident in standing long jumps in both sexes. Age-by-year interactions were statistically significant for agility in both sexes, with significant differences occurring at different ages. These trends did not change when adjusted for temporal changes in height and weight. Our research provides important data for local governments to implement public policies and practices to improve physical fitness levels in children.

Genotyped indigenous Kiwcha adults at high altitude are lighter and shorter than their low altitude counterparts

Background

Anthropometric measures have been classically used to understand the impact of environmental factors on the living conditions of individuals and populations. Most reference studies on development and growth in which anthropometric measures were used were carried out in populations that are located at sea level, but there are few studies carried out in high altitude populations.

Objective

The objective of this study was to evaluate the anthropometric and body composition in autochthonous Kiwcha permanently living at low and high altitudes.

Methodology

A cross-sectional study of anthropometric and body composition between genetically matched lowland Kiwcha from Limoncocha (n = 117), 230 m in the Amazonian basin, and high-altitude Kiwcha from Oyacachi (n = 95), 3800 m in Andean highlands. Student’s t-test was used to analyze the differences between continuous variables, and the chi-square test was performed to check the association or independence of categorical variables. Fisher’s exact test or Spearman’s test was used when the variable had evident asymmetries with histograms prior to the selection of the test.

Results

This study shows that high altitude men are shorter than their counterparts who live at low altitude, with p = 0.019. About body muscle percentage, women at high altitudes have less body muscle percentage (− 24.8%). In comparison, men at high altitudes have significantly more muscle body mass percentage (+ 13.5%) than their lowland counterparts. Body fat percentage was lower among low altitude women (− 15.5%), and no differences were found among men.

Conclusions

This is the first study to be performed in two genotyped controlled matching populations located at different altitudes to our best knowledge. The anthropometric differences vary according to sex, demonstrating that high altitude populations are, in general, lighter and shorter than their low altitude controls. Men at high altitude have more muscled bodies compared to their lowland counterparts, but their body age was older than their actual age.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40101-022-00280-6.

Parallel evolution in human populations: A biocultural perspective

Parallel evolution-where different populations evolve similar traits in response to similar environments-has been a topic of growing interest to biologists and biological anthropologists for decades. Parallel evolution occurs in human populations thanks to myriad biological and cultural mechanisms that permit humans to survive and thrive in diverse environments worldwide. Because humans shape and are shaped by their environments, biocultural approaches that emphasize the interconnections between biology and culture are key to understanding parallel evolution in human populations as well as the nuances of human biological variation and adaptation. In this review, we discuss how biocultural theory has been and can be applied to studies of parallel evolution and adaptation more broadly. We illustrate this through four examples of parallel evolution in humans: malaria resistance, lactase persistence, cold tolerance, and high-altitude adaptation.

Studying latent change process in height growth of children in Ethiopia, India, Peru and Vietnam

BACKGROUND

Anthropometric measurements of healthy children differ in different parts of the world due to the diverse ethnicity and cultural backgrounds of families. In longitudinal studies, appropriate modeling of repeated anthropometric measures can improve the understanding of patterns of change, determinants of patterns, and variations in patterns of change over time. The objective of this study was to examine the latent change in physical height of children in Ethiopia, India, Peru, and Vietnam.

METHOD

Longitudinal data of 6601 children aged 1 to 15 years were obtained from the Young Lives cohort study. The data were analyzed using a latent basis growth curve model.

RESULTS

The findings of the study revealed that the rates of growth did not remain constant across the time intervals, which indicates the nonlinearity of the growth trajectory over time. For instance, children had the highest rate of growth between age 1 and 5 years, then between age 8 and 12 years, and a low rate of growth was observed between age 12 and 15 years. At the first measurement occasion (age 1 year) females were 0.826 cm (p < 0.0001) times shorter than males. The mean height at one year of age ranged from 72.13 cm in Ethiopia to 72.62 cm in India. Children in India and Vietnam had higher mean height at age one year. However, no significant difference in mean height at age one year was found between Ethiopian and Peruvian children, ([Formula: see text]). Peruvian and Vietnamese children grew at a faster rate, while Indian children grew at a slower rate than Ethiopian children.

CONCLUSION

We found substantial latent growth variations among children in four low- and middle-income countries. The latent trajectories differed by gender and country. The outcomes of the study could aid in detecting inequalities in children's height growth.

Socioeconomic impacts on Andean adolescents’ growth

Background/Objectives

We evaluated potential socioeconomic contributors to variation in Andean adolescents’ growth between households within a peri-urban community undergoing rapid demographic and economic change, between different community types (rural, peri-urban, urban) and over time. Because growth monitoring is widely used for assessing community needs and progress, we compared the prevalences of stunting, underweight, and overweight estimated by three different growth references.

Methods

Anthropometrics of 101 El Alto, Bolivia, adolescents (Alteños), 11.0–14.9 years old in 2003, were compared between households (economic status assessed by parental occupations); to one urban and two rural samples collected in 1983/1998/1977, respectively; and to the WHO growth reference, a representative sample of Bolivian children (MESA), and a region-wide sample of high-altitude Peruvian children (Puno).

Results

Female Alteños’ growth was positively associated with household and maternal income indices. Alteños’ height averaged ∼0.8SD/∼0.6SD/∼2SDs greater than adolescents’ height in urban and rural communities measured in 1983/1998/1977, respectively. Overweight prevalence was comparable to the WHO, and lower than MESA and Puno, references. Stunting was 8.5/2.5/0.5 times WHO/MESA/Puno samples, respectively.

Conclusions/Implications

Both peri-urban conditions and temporal trends contributed to gains in Alteños’ growth. Rural out-migration can alleviate migrants’ poverty, partly because of more diverse economic options in urbanized communities, especially for women. Nonetheless, Alteños averaged below WHO and MESA height and weight medians. Evolved biological adaptations to environmental challenges, and the consequent variability in growth trajectories, favor using multiple growth references. Growth monitoring should be informed by community- and household-level studies to detect and understand local factors causing or alleviating health disparities.

Regional variation in growth status. The Peruvian health and optimist growth study

OBJECTIVE

This study aims to (1) investigate differences in weight, body mass index (BMI), and waist circumference (WC) among Peruvian children and adolescents living in three areas located at different altitudes; (2) compare age- and sex-specific height, weight, and BMI within each site with US reference data.

METHODS

We sampled 8753 subjects (4130 boys), aged 4 to 17 years from sea level, rainforest, and high-altitude. Height, weight, and WC were measured and BMI was calculated. Analysis of variance was used to compare variables across geographic regions, and the Hoff and Blackburn procedure was used to compare the Peruvian results with US reference data.

RESULTS

Participants living at sea level were taller, heavier, had greater BMI and WC relative to those living at high-altitude and in the rainforest. Peruvian schoolchildren of both sexes from the three geographical areas were shorter and lighter than their American peers. Boys and girls living in the rainforest and at high-altitude had lower BMI, whereas WC values of American schoolchildren are higher than those of the Peruvian children by age and gender.

CONCLUSIONS

Peruvians living at different altitudes differ in their growth indicators (height, weight, BMI, and WC), with significant differences between those living at sea level relative to their peers from other regions. Further, Peruvian schoolchildren of both sexes from the three geographical areas significantly differ from their US counterparts.

Hematological Parameters, Lipid Profile, and Cardiovascular Risk Analysis Among Genotype-Controlled Indigenous Kiwcha Men and Women Living at Low and High Altitudes

Introduction: Human adaptation to high altitude is due to characteristic adjustments at every physiological level. Differences in lipid profile and cardiovascular risk factors in altitude dwellers have been previously explored. Nevertheless, there are no reports available on genotype-controlled matches among different altitude-adapted indigenous populations.

Objective: To explore the possible differences in plasma lipid profile and cardiovascular risk among autochthonous Kiwcha people inhabitants of low and high-altitude locations.

Methodology: A cross-sectional analysis of plasmatic lipid profiles and cardiovascular risk factors in lowland Kiwchas from Limoncocha (230 m) and high-altitude Kiwchas from Oyacachi (3,800 m).

Results: In the low altitude group, 66% were women (n = 78) and 34% (n = 40) were men, whereas in the high altitude group, 59% (n = 56) were women and 41% (n = 41%) were men. We found the proportion of overweight and obese individuals to be higher among low altitude dwellers (p < 0.05). Red blood cells (RBCs), hemoglobin concentration, and SpO₂% were higher among high altitude dwellers and the erythrocyte size was found to be smaller at high altitude. The group located at low altitude also showed lower levels of plasma cholesterol, low-density lipoprotein (LDL), and high-density lipoprotein (HDL), but most of these differences are not influenced by gender or elevation.

Conclusions: Living at an altitude elicits well-known adaptive physiological changes such as erythrocyte count, hemoglobin concentration, hematocrit level, and serum glucose level. We also report clinical differences in the plasma lipid profile, with higher levels of cholesterol, HDL, and LDL in inhabitants of the Andes Mountain vs. their Amazonian basin peers. Despite this, we did not find significant differences in cardiovascular risk.

Malnutrition, illness, poverty, and infant growth: A test of a syndemic hypothesis in Nuñoa, Peru

The concept of syndemics provides an important framework for understanding the complex interactions of biological and social conditions. Its use in public health and epidemiological research has increased substantially in the past ten years. Many syndemic analyses rely on the use of a sum score and subsequently fail to demonstrate biological interaction, leading some scholars to question the utility of the syndemic approach. Here, we utilize data from 86 mother/infant pairs from the rural district of Nuñoa, Peru to test a potential syndemic relationship among infection, malnutrition and infant growth. Between 2014 and 2015, surveys were conducted to assess household wealth, sanitation, dietary diversity, and reported illness, while anthropometric measures of mothers and infants were conducted to assess nutritional status via height-for-age and weight-for-height z-scores. Ethnographic insight was used in the selection of key economic variables including the development of an agricultural wealth index. We then assessed whether this constellation of health outcomes met the criteria for a syndemic by performing a quantitative analysis in which we tested for (1) an association between economic marginalization and high-risk environments; (2) the concentration of malnutrition, poor growth, and infection; and (3) biological interaction among these health outcomes. We found that economic measures were associated with pathogenic and nutritional risk, and that these in turn were associated with infectious disease, nutritional status, and growth. However, we did not find evidence that the proposed syndemic met criteria (2) or (3). We conclude that, despite being both socially and biologically plausible, a syndemic of malnutrition, poor growth, and infection did not exist in this context. This analysis moves syndemic research forward by demonstrating that such hypotheses are falsifiable, thus presenting a process by which they may be tested and lending support to the use of syndemic theory as an effective analytic framework.

Trekking and toddlers: Towards a biocultural analysis of growth among infants and young children in a rural region of the Himalayas

OBJECTIVES

Rapid socioeconomic change, associated with development and a growing tourism industry is occurring across the Himalayas. The health impact of this rapid economic development is poorly understood, especially for infants and young children. This study investigated the associations between village level economic differences as indexed by economic development and tourism engagement on infant and young child growth and health in a population of ethnic Tibetans living in the western Himalayas of Nepal.

METHODS

One hundred and fifty nine infants and young children (ages 1-24 months) were enrolled. Anthropometric data (height, weight, triceps skinfold thickness) were collected at a single time point. Village level measurements of tourism and market engagement were incorporated into a scale measuring tourism, healthcare, trail access, agriculture, and involvement in medicinal trade. Village level disease patterns were calculated from morbidity and mortality recalls collected since 2003.

RESULTS

There were no significant associations between infant weight for age z-score (WAZ), length for age z-score (LAZ), or weight-for-length for age z-score (WLZ) and village altitude, village economic development score, or engagement in tourism. Males had significantly higher LAZ, WAZ, and WLZ compared to females; only females showed a decline in LAZ with age. Triceps skinfold thickness z-score (ZTSF) was inversely associated with village level economic development score in male but not female infants; females ZTSF was positively associated with IYC age.

CONCLUSIONS

While overall size for age indices (WAZ, LAZ, WLZ) were not associated with altitude or village economic development in this population, ZTSF was inversely associated with village economic development in males but not females.

A biocultural examination of home food production and child growth in highland Peru

OBJECTIVES

Chronic malnutrition remains a persistent global health issue. This mixed methods investigation in rural Peru examines the role of home food production (HFP) in reducing child malnutrition by testing the following hypotheses: (a) higher HFP will be associated with higher infant z-scores than those with less HFP and (b) infants with higher HFP will exhibit improved longitudinal growth outcomes across 6 months.

METHODS

Ethnographic methods include semi-structured interviews and participant observation. A household survey and anthropometric data were collected twice, from 86 infants under of 24 months old. A HFP index (HFI) was generated based on reports of animals for meat consumption, eggs, milk, and agricultural products for home consumption. Kruskal-Wallis tests were used to examine patterns of HFI and infant anthropometrics. Multivariate regressions were used to examine the relationships between HFP and infant height for age (HAZ), weight for age (WAZ), and triceps skinfold for age (TSAZ) in both rounds and 6-month change between rounds (6MΔ).

RESULTS

There were no relationships between HFI and infant z-scores in round one, however, HFI was significantly positively related to HAZ (B = 0.091, P < .039) in round two and with 6MΔ in HAZ (B = 0.09, P < .047). HFI did not predict WAZ or TSAZ in either round.

CONCLUSIONS

HFP represents an important influence of infant growth in Nuñoa, likely through nutritional improvement due to increased availability of animal-sourced foods and through contribution to household economy and maternal empowerment.

Child Growth Curves in High-Altitude Ladakh: Results from a Cohort Study

High prevalence of child underweight and stunting in high-altitude areas has often been reported. However, most previous studies on this topic were cross-sectional. Another critical concern is that using the World Health Organization (WHO) Child Growth Standards to evaluate child growth in high-altitude areas may lead to overestimations of underweight and stunting. Our study aimed to evaluate the long-term growth pattern of children (3 to 18 years) above the altitude of 3500 m in Ladakh, India. The participants’ body weight (BW), body height (BH), and body mass index (BMI) were measured annually according to the WHO Child Growth Standards for children under 5 years old and the WHO reference data for children aged 5 to 19 years. The generalized estimating equation (GEE) was used to estimate the means and z-scores of BW, BH, and BMI at different ages. A total of 401 children were enrolled from 2012 to 2018. Their mean z-scores of BW, BH, and BMI were −1.47, −1.44, and −0.85 in 2012 and increased to −0.74, −0.92, and −0.63 in 2018. This population’s specific growth curve was also depicted, which generally fell below the 85th percentile of the WHO standards. This is the first cohort study about long-term child growth patterns in a high-altitude area. The detailed underlying mechanisms of our findings need future research on more representative data of high-altitude populations.

Low Elevation and Physical Inactivity are Associated with a Higher Prevalence of Metabolic Syndrome in Ecuadorian Adults: A National Cross-Sectional Study

BACKGROUND

Elevation and health-related lifestyles have been associated with the development of metabolic syndrome (MetS). However, such associations have not been investigated extensively in a global context. The present study aimed to determine the associations among elevation of residence, health-related lifestyles, and the risk of MetS in an Ecuadorian adult population.

SUBJECTS AND METHODS

This cross-sectional study was conducted utilizing secondary data from the 2012 Ecuador National Health and Nutrition Survey (ENSANUT-ECU). A total of 6024 adults (1964 men and 4060 women) 20 to 60 years old were included in the study. Elevation was obtained by georeferencing techniques and categorized into low (0-2000 masl) and high (>2001 masl). Dietary intake was measured using a 24-hour recall and health-related lifestyle via risk and physical activity standardized questionnaire. MetS was defined on the basis of the National Cholesterol Education Program Adult Treatment Panel III and the Latin American Diabetes Association criteria. Multiple logistic regression analyses were used to examine whether elevation of residence and health-related lifestyles can increase the risk of MetS.

RESULTS

Residing at low elevation increased prevalence of MetS in men (1.37; 95% CI, 1.05-1.76) and elevated fasting glucose in both men (1.80; 95% CI, 1.32-2.46) and women (1.55; 95% CI, 1.24-1.93) after adjusting for confounders. Additionally, a lack of physical activity was identified as an important factor that raises the risk of increased waist circumference in both men (2.05; 95% CI, 1.22-3.45) and women (1.38; 95% CI, 1.05-1.83) living at low elevation.

CONCLUSION

Our findings suggest that low elevation of residence and physical inactivity are associated with a higher prevalence of MetS in Ecuadorian adults.

Building on the biocultural syntheses: 20 years and still expanding

Building a New Biocultural Synthesis: Political Economic Perspectives in Human Biology called for an integration of political economy with ecological and adaptability perspectives in biocultural anthropology. A major goal of this volume was to explore the utility of including political-economic and sociocultural processes in analyses of human biological variation, nutrition, and health. A second goal was to enhance collaboration among subfields and work against the "chasm" that separated complementary perspectives in cultural and biological anthropology. Twenty years hence, new ways to link social inequalities and human biology have emerged in part through contributions of developmental origins of health and disease, epigenetics, microbiomes, and other new methods for tracing pathways of embodiment. Equally important, notions of "local/situated biologies" and "reactive genomes," provide frameworks for understanding biology and health at the nexus of ecologies, societies, and histories. We review and highlight these contributions toward expanding critical approaches to human biology. Developments over the past two decades have reinforced the central role of social environments and structural inequalities in shaping human biology and health. Yet, within biocultural approaches, a significant engagement with historical, political-economic, and sociocultural conditions remains relatively rare. We review potential barriers to such analyses, focusing on theoretical and methodological challenges as well as the subfield structure of anthropology. Achieving politically and socially contextualized and relevant critical biocultural approaches remains a challenge, but there is reason for optimism amid new theoretical and methodological developments and innovations brought by new generations of scholars.