Bringing the lab bench to the field: Point-of-care testing for enhancing health research and stakeholder engagement in rural/remote, indigenous, and resource-limited contexts.

Point-of-care testing (POCT) allows researchers and health-care providers to bring the lab bench to the field, providing essential health information that can be leveraged to improve health care, accessibility, and understanding across clinical and research settings. Gaps in health service access are most pronounced in what we term RIR settings-rural/remote regions, involving Indigenous peoples, and/or within resource-limited settings. In these contexts, morbidity and mortality from infectious and non-communicable diseases are disproportionately higher due to numerous geographic, economic, political, and sociohistorical factors. Human biologists and global health scholars are well-positioned to contribute on-the-ground-level insights that can serve to minimize global health inequities and POCT has the potential to augment such approaches. While the clinical benefits of POCT include increasing health service access by bringing testing, rapid diagnosis, and treatment to underserved communities with limited pathways to centralized laboratory testing, POCT also provides added benefits to both health-focused researchers and their participants. Through portable, minimally invasive devices, researchers can provide actionable health data to participants by coupling POCT with population-specific health education, discussing results and their implications, creating space for participants to voice concerns, and facilitating linkages to treatment. POCT can also strengthen human biology research by shedding light on questions of evolutionary and biocultural importance. Here, we expand on the epidemiological and research value, as well as practical and ethical challenges of POCT across stakeholders (i.e., participant, community, health researcher, and trainee). Finally, we emphasize the immense opportunities of POCT for fostering collaborative research and enhancing access to health delivery and information and, by extension, helping to mitigate persistent global health inequities.

Childhood Daily Energy Expenditure Does Not Decrease with Market Integration and Is Not Related to Adiposity in Amazonia.

BACKGROUND: Childhood overweight and obesity (OW/OB) is increasingly centered in low- and middle-income countries (LMICs) as rural populations experience market integration and lifeway change. Most explanatory studies have relied on imprecise estimates of children's energy expenditure, restricting understanding of the relative effects of changes in diet and energy expenditure on the development of OW/OB in transitioning contexts. OBJECTIVES: This study used gold-standard measurements of children's energy expenditure to investigate the changes that underlie OW/OB and the nutrition/epidemiologic transition. METHODS: Cross-sectional data were collected from "rural" (n = 43) Shuar forager-horticulturalist children and their "peri-urban" (n = 34) Shuar counterparts (age 4-12 y) in Amazonian Ecuador. Doubly labeled water measurements of total energy expenditure (TEE; kcal/d), respirometry measurements of resting energy expenditure (REE; kcal/d), and measures of diet, physical activity, immune activity, and market integration were analyzed primarily using regression models. RESULTS: Peri-urban children had higher body fat percentage (+8.1%, P < 0.001), greater consumption of market-acquired foods (multiple P < 0.001), lower concentrations of immune activity biomarkers (multiple P < 0.05), and lower REE (-108 kcal/d, P = 0.002) than rural children. Despite these differences, peri-urban children's TEE was indistinguishable from that of rural children (P = 0.499). Moreover, although sample-wide IgG concentrations and household incomes predicted REE (both P < 0.05), no examined household, immune activity, or physical activity measures were related to children's overall TEE (all P > 0.09). Diet and energy expenditure associations with adiposity demonstrate that only reported consumption of market-acquired "protein" and "carbohydrate" foods predicted children's body fat levels (multiple P < 0.05). CONCLUSIONS: Despite underlying patterns in REE, Shuar children's TEE is not reliably related to market integration and-unlike dietary measures-does not predict adiposity. These findings suggest a leading role of changing dietary intake in transitions to OW/OB in LMICs.

Measuring subjective social status in children of diverse societies.

Subjective Social Status (SSS) is a robust predictor of psychological and physiological outcomes, frequently measured as self-reported placement on the MacArthur Scale of Subjective Social Status. Despite its importance, however, there are still open questions regarding how early into ontogeny SSS can be measured, and how well SSS measures can be extended to non-Western and small-scale populations. Here, we investigate the internal consistency of responses to the MacArthur ladder across four cultures by comparing responses to more explicit social comparison questions. We conduct these comparisons among children and adolescents, ages 4 to 18, in India, the United States, and Argentina, in addition to those in two indigenous communities of the Ecuadorean Amazon marked by differing degrees of market integration (total N = 363). We find that responses are consistent in all populations, except for the more remote forager-horticulturalist Ecuadorian community. We also find that, consistent with findings among American adolescents, SSS declines with age. We then assess the test-retest reliability of the MacArthur Scale across two time-points: a subset of Indian participants (N = 43) within one week, and a larger, second sample of Indian participants after one year (N = 665). We find that responses are highly correlated within one week (ρ = 0.47), and moderately correlated after one year (ρ = 0.32). These results suggest that responses to the MacArthur ladder are internally consistent and reliable among children across a range of diverse populations, though care must be taken in utilizing these measures among children of non-industrial, small-scale societies.

Constraint and trade-offs regulate energy expenditure during childhood.

Children's metabolic energy expenditure is central to evolutionary and epidemiological frameworks for understanding variation in human phenotype and health. Nonetheless, the impact of a physically active lifestyle and heavy burden of infectious disease on child metabolism remains unclear. Using energetic, activity, and biomarker measures, we show that Shuar forager-horticulturalist children of Amazonian Ecuador are ~25% more physically active and, in association with immune activity, have ~20% greater resting energy expenditure than children from industrial populations. Despite these differences, Shuar children's total daily energy expenditure, measured using doubly labeled water, is indistinguishable from industrialized counterparts. Trade-offs in energy allocation between competing physiological tasks, within a constrained energy budget, appear to shape childhood phenotypic variation (e.g., patterns of growth). These trade-offs may contribute to the lifetime obesity and metabolic health disparities that emerge during rapid economic development.

Market Integration Predicts Human Gut Microbiome Attributes across a Gradient of Economic Development.

Economic development is marked by dramatic increases in the incidence of microbiome-associated diseases, such as autoimmune diseases and metabolic syndromes, but the lifestyle changes that drive alterations in the human microbiome are not known. We measured market integration as a proxy for economically related lifestyle attributes, such as ownership of specific market goods that index degree of market integration and components of traditional and nontraditional (more modern) house structure and infrastructure, and profiled the fecal microbiomes of 213 participants from a contiguous, indigenous Ecuadorian population. Despite relatively modest differences in lifestyle across the population, greater economic development correlated with significantly lower within-host diversity, higher between-host dissimilarity, and a decrease in the relative abundance of the bacterium Prevotella. These microbiome shifts were most strongly associated with more modern housing, followed by reduced ownership of traditional subsistence lifestyle-associated items. IMPORTANCE Previous research has reported differences in the gut microbiome between populations residing in wealthy versus poorer countries, leading to the assertion that lifestyle changes associated with economic development promote changes in the gut microbiome that promote the proliferation of microbiome-associated diseases. However, a direct relationship between economic development and the gut microbiome has not previously been shown. We surveyed the gut microbiomes of a single indigenous population undergoing economic development and found significant associations between features of the gut microbiome and lifestyle changes associated with economic development. These findings suggest that even the earliest stages of economic development can drive changes in the gut microbiome, which may provide a warning sign for the development of microbiome-associated diseases.

Heterogeneous effects of market integration on sub-adult body size and nutritional status among the Shuar of Amazonian Ecuador.

BACKGROUND: Market integration (MI)-increasing production for and consumption from a market-based economy-is drastically altering traditional ways of life and environmental conditions among indigenous Amazonian peoples. The effects of MI on the biology and health of Amazonian children and adolescents, however, remain unclear. AIM: This study examines the impact of MI on sub-adult body size and nutritional status at the population, regional and household levels among the Shuar of Amazonian Ecuador. SUBJECTS AND METHODS: Anthropometric data were collected between 2005-2014 from 2164 Shuar (aged 2-19 years) living in two geographic regions differing in general degree of MI. High-resolution household economic, lifestyle and dietary data were collected from a sub-sample of 631 participants. Analyses were performed to investigate relationships between body size and year of data collection, region and specific aspects of household MI. RESULTS: Results from temporal and regional analyses suggest that MI has a significant and overall positive impact on Shuar body size and nutritional status. However, household-level results exhibit nuanced and heterogeneous specific effects of MI underlying these overarching relationships. CONCLUSION: This study provides novel insight into the complex socio-ecological pathways linking MI, physical growth and health among the Shuar and other indigenous Amazonian populations.

Human preferences for sexually dimorphic faces may be evolutionarily novel.

A large literature proposes that preferences for exaggerated sex typicality in human faces (masculinity/femininity) reflect a long evolutionary history of sexual and social selection. This proposal implies that dimorphism was important to judgments of attractiveness and personality in ancestral environments. It is difficult to evaluate, however, because most available data come from large-scale, industrialized, urban populations. Here, we report the results for 12 populations with very diverse levels of economic development. Surprisingly, preferences for exaggerated sex-specific traits are only found in the novel, highly developed environments. Similarly, perceptions that masculine males look aggressive increase strongly with development and, specifically, urbanization. These data challenge the hypothesis that facial dimorphism was an important ancestral signal of heritable mate value. One possibility is that highly developed environments provide novel opportunities to discern relationships between facial traits and behavior by exposing individuals to large numbers of unfamiliar faces, revealing patterns too subtle to detect with smaller samples.

Soil-transmitted helminth prevalence and infection intensity among geographically and economically distinct Shuar communities in the Ecuadorian Amazon.

Soil-transmitted helminth (STH) infections can result in a variety of negative health outcomes (e.g., diarrhea, nutritional deficiencies). Market integration (MI; participation in market-based economies) has been suggested to alter levels of STH exposure due to associated changes in diet, sanitation, and behavior, but the effects are complicated and not well understood. Some effects of economic development result in decreased exposure to certain pathogens, and other factors can lead to higher pathogen exposure. With geographic location used as a proxy, the present study investigates the effects of economic development on parasite load among an indigenous population at multiple points along the spectrum of MI. This research has many implications for public health, including an increased understanding of how social and economic changes alter disease risk around the world and how changing parasite load affects other health outcomes (i.e., allergy, autoimmunity). Specifically, this study examines the prevalence of intestinal helminths among the Shuar, an indigenous group in the Morona-Santiago region of Ecuador, from 2 geographically/economically separated areas, with the following objectives: (1) report STH infection prevalence and intensity among Shuar; (2) explore STH infection prevalence and intensity as it relates to age distribution in the Shuar population; (3) compare STH infection patterns in geographically and economically separated Shuar communities at different levels of MI. Kato-Katz thick smears were made from fresh stool samples and examined to determine STH presence/intensity. Results indicate that 65% of the 211 participants were infected with at least 1 STH. Twenty-five percent of the sample had coinfections with at least 2 species of helminth. Infection was more common among juveniles (<15 yr) than adults. Infection prevalence and intensity was highest among more isolated communities with less market access. This study documents preliminary associations between STH infection and exposure to MI, with implications for public health research and interventions.

Implications of market integration for cardiovascular and metabolic health among an indigenous Amazonian Ecuadorian population.

BACKGROUND: Market integration (MI), the suite of social and cultural changes that occur with economic development, has been associated with negative health outcomes such as cardiovascular disease; however, key questions remain about how this transition manifests at the local level. AIM: The present paper investigates the effects of MI on health among Shuar, an indigenous lowland Ecuadorian population, with the goal of better understanding the mechanisms responsible for this health transition. SUBJECTS AND METHODS: This study examines associations between measures of MI and several dimensions of cardiovascular and metabolic health (fasting glucose, lipids [LDL, HDL and total cholesterol; triglycerides] and blood pressure) among 348 adults. RESULTS: Overall, Shuar males and females have relatively favourable cardiovascular and metabolic health. Shuar who live closer to town have higher total (p < 0.001) and HDL cholesterol (p < 0.001), while Shuar in more remote regions have higher diastolic blood pressure (p = 0.007). HDL cholesterol is positively associated with consumption of market foods (r = 0.140; p = 0.045) and ownership of consumer products (r = 0.184; p = 0.029). CONCLUSIONS: This study provides evidence that MI among Shuar is not a uniformly negative process but instead produces complex cardiovascular and metabolic health outcomes.

Illness, injury, and disability among Shiwiar forager-horticulturalists: implications of health-risk buffering for the evolution of human life history.

Human life history is distinguished by long lifespan, delayed reproduction, intergenerational asymmetric benefit transfers from adults to juveniles and between adults, and a large brain able to engage in unprecedented levels of learning, reasoning, and insight. The evolution of these traits depends on relatively low human mortality. Understanding why humans have low mortality is therefore critical for understanding the evolution of key human traits. One explanation is that the evolution of food provisioning during periods of health crisis reduced mortality. This hypothesis turns on health risk having posed a significant adaptive problem that could be effectively buffered by healthcare provisioning. Unfortunately, the frequency, duration, and fitness effects of temporary disability are difficult to estimate based on osteological evidence alone, and systematic ethno-biological research on these issues among extant small-scale societies with little access to Western medical care is lacking. Here I present data on 678 injuries and illnesses suffered by 40 Shiwiar forager-horticulturalists, based on physical evidence and informant reports. A subsample of 17 individuals provided data on incidence and duration of disability for 215 pathological incidents. Results indicate that injury and illness occur frequently across the lifespan. Most living individuals have suffered temporarily disabling health crises likely to have been lethal without provisioning. The fitness effects of surviving these episodes are high, suggesting that the Shiwiar population structure and lifeway are dependent on infrequent extended provisioning to temporarily disabled individuals, and that provisioning of aid during healthcare crises effectively lowers mortality in this small-scale society.