The relationship between altitude and BMI varies across low- and middle-income countries.

OBJECTIVES: Studies suggest that living at high altitude decreases obesity risk, but this research is limited to single-country analyses. We examine the relationship between altitude and body mass index (BMI) among women living in a diverse sample of low- and middle-income countries. MATERIALS AND METHODS: Using Demographic and Health Survey data from 1 583 456 reproductive age women (20-49 years) in 54 countries, we fit regression models predicting BMI and obesity by altitude controlling for a range of demographic factors-age, parity, breastfeeding status, wealth, and education. RESULTS: A mixed-effects model with country-level random intercepts and slopes predicts an overall -0.162 kg/m2 (95% CI -0.220, -0.104) reduction in BMI and lower odds of obesity (OR 0.90, 95% CI 0.87, 0.95) for every 200 m increase in altitude. However, countries vary dramatically in whether they exhibit a negative or positive association between altitude and BMI (34 countries negative, 20 positive). Mixed findings also arise when examining odds of obesity. DISCUSSION: We show that past findings of declining obesity risk with altitude are not universal. Increasing altitude predicts slightly lower BMIs at the global level, but the relationship within individual countries varies in both strength and direction.

Starting from scratch in a patrilocal society: how women build networks after marriage in rural Bangladesh.

Humans rely on both kin and non-kin social ties for a wide range of support. In patrilocal societies that practice village exogamy, women can face the challenge of building new supportive networks when they move to their husband's village and leave many genetic kin behind. In this paper, we track how women from 10 diverse communities in rural Bangladesh build supportive networks after migrating to their husband's village, comparing their trajectories with women who remained in their childhood village (Bengali: n = 317, Santal: n = 36, Hajong: n = 39, Mandi: n = 36). Women who migrated for marriage started with almost no adult close kin (mean 0.1) compared to women who remained in their childhood village (mean 2.4). However, immigrants compensated for the lack of genetic kin by a combination of close affinal kin and close friends. By their late 20s, immigrants reported substantially more non-kin friends than did non-immigrants (mean 1.4 versus 1.1) and a comparable number of supportive partners in several domains. These findings raise questions about the functions and quality of these different social ties and how different composition of supportive networks may provide different opportunities for women in these settings. This article is part of the theme issue 'Cooperation among women: evolutionary and cross-cultural perspectives'.

One size does not fit all. How universal standards for normal height can hide deprivation and create false paradoxes.

Public health practitioners and social scientists frequently compare height against one-size-fits-all standards of human growth to assess well-being, deprivation, and disease risk. However, underlying differences in height can make some naturally tall populations appear well-off by universal standards, even though they live in severe states of deprivation. In this article, I describe the worldwide extent of these population differences in height and illustrate how using a universal yardstick to compare population height can create puzzling disparities (eg, between South Asia and sub-Saharan Africa) while also underestimating childhood stunting in specific world regions (eg, West Africa and Haiti). I conclude by discussing potential challenges of developing and implementing population-sensitive standards for assessing healthy development.

Comparing hemoglobin distributions between population-based surveys matched by country and time.

BACKGROUND: Valid measurement of hemoglobin is important for tracking and targeting interventions. This study compares hemoglobin distributions between surveys matched by country and time from The Demographic and Health Survey (DHS) Program and the Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia (BRINDA) project. METHODS: Four pairs of nationally representative surveys measuring hemoglobin using HemoCue® with capillary (DHS) or venous (BRINDA) blood were matched by country and time. Data included 17,719 children (6-59 months) and 21,594 non-pregnant women (15-49 y). Across paired surveys, we compared distributional statistics and anemia prevalence. RESULTS: Surveys from three of the four countries showed substantial differences in anemia estimates (9 to 31 percentage point differences) which were consistently lower in BRINDA compared to DHS (2 to 31 points for children, 1 to 16 points for women). CONCLUSION: We identify substantial differences in anemia estimates from surveys of similar populations. Further work is needed to identify the cause of these differences to improve the robustness of anemia estimates for comparing populations and tracking improvements over time.

Agricultural wealth better predicts mental wellbeing than market wealth among highly vulnerable households in Haiti: Evidence for the benefits of a multidimensional approach to poverty.

OBJECTIVES: Lack of wealth (poverty) impacts almost every aspect of human biology. Accordingly, many studies include its assessment. In almost all cases, approaches to assessing poverty are based on lack of success within cash economies (eg, lack of income, employment). However, this operationalization deflects attention from alternative forms of poverty that may have the most substantial influence on human wellbeing. We test how a multidimensional measure of poverty that considers agricultural assets expands the explanatory power of the construct of household poverty by associating it with one key aspect of wellbeing: symptoms of mental health. METHODS: We used the case of three highly vulnerable but distinctive communities in Haiti-urban, town with a rural hinterland, and rural. Based on survey responses from adults in 4055 geographically sampled households, linear regression models were used to predict depression and anxiety symptom levels controlling for a wide range of covariates related to detailed measures of material poverty, including cash-economy and agricultural assets, income, financial stress, and food insecurity. RESULTS: Household assets related to the cash economy were significantly associated with lower (ie, better) depression scores (-0.7, [95% CI: -1.2 to, -0.1]) but unrelated to anxiety scores (-0.3 [95% CI: -0.8 to 0.3]). Agricultural wealth was significantly-and more strongly-associated with both reductions in depression symptoms (-1.4 [95% CI: -2.2 to -0.7]) and anxiety symptoms (-1.8 [95% CI: -2.6 to -1.0]). These associations were consistent across the three sites, except in the fully urban site in Port-au-Prince where level of depression symptoms was not significantly associated with household agricultural wealth. CONCLUSIONS: Standard measures of poverty based on success in the cash economy can mask important associations between poverty and wellbeing, in this case related to household-level subsistence capacity and crucial food-producing household assets.

Disentangling basal and accrued height-for-age for cross-population comparisons.

OBJECTIVES: Current standards for comparing stunting across human populations assume a universal model of child growth. Such comparisons ignore population differences that are independent of deprivation and health outcomes. This article partitions variation in height-for-age that is specifically associated with deprivation and health outcomes to provide a basis for cross-population comparisons. MATERIALS AND METHODS: Using a multilevel model with a sigmoid relationship of resources and growth, we partition variation in height-for-age z-scores (HAZ) from 1.5 million children across 70 countries into two components: (1) "accrued HAZ" shaped by environmental inputs (e.g., undernutrition, infectious disease, inadequate sanitation, poverty) and (2) a country-specific "basal HAZ" independent of such inputs. We validate these components against population-level infant mortality rates and assess how these basal differences may affect cross-population comparisons of stunting. RESULTS: Basal HAZ differs reliably across countries (range of approximately 1.5 SD) and is independent of measures of infant mortality. By contrast, accrued HAZ captures stunting as impaired growth due to deprivation and is more closely associated with infant mortality than observed HAZ. Assessing stunting prevalence by accrued HAZ suggest that populations in West Africa and Haiti suffer much greater levels of stunting than indicated by observed HAZ. DISCUSSION: Current universal standards may dramatically underestimate stunting in populations with taller basal HAZ. Relying on observed HAZ rather than accrued HAZ may also lead to inappropriate cross-population comparisons, such as concluding that Haitian children enjoy better conditions for growth than do Indian or Guatemalan children.

Identifying the limits to socioeconomic influences on human growth.

Contemporary humans occupy the widest range of socioeconomic environments in their evolutionary history, and this has revealed unprecedented environmentally-induced plasticity in physical growth. This plasticity also has limits, and identifying those limits can help researchers: (1) parse when population differences arise from environmental inputs or not and (2) determine when it is possible to infer socioeconomic disparities from disparities in body form. To illustrate potential limits to environmental plasticity, we analyze body mass index (BMI) and height data from 1,768,962 women and 207,341 men (20-49 y) living in households exhibiting 1000-fold variation in household wealth (51 countries, 1985-2017, 164 surveys) across four world regions-sub-Saharan Africa, South Asia, Latin America, and North Africa and the Middle East. We find that relationships of environmental inputs with both mean height and BMI bottom out at roughly 100-700 USD per capita household wealth (2011 international units, PPP), but at different basal BMIs and basal heights for different regions. The relationship with resources tops out for BMI at around 20 K-35 K USD for women, with growth potential due to environmental inputs in the range of 6.2-8.4 kg/m2. By contrast, mean BMI for men and mean height for both sexes remains sensitive to environmental inputs even at levels far above the low- and middle-income samples studied here. This suggest that further work integrating comparable data from low- and high-income samples should provide a better picture of the full range of environmental inputs on human height and BMI. We conclude by discussing how neglecting such population-specific limits to human growth can lead to erroneous inferences about population differences.

Worldwide fertility declines do not rely on stopping at ideal parities.

A key demographic hypothesis has been that fertility declines rely on stopping at target parities, but emerging evidence suggests that women frequently reduce fertility without specific numeric targets. To assess the relative importance of these two paths to fertility decline, we develop a novel mixture model to estimate: (1) the proportion of women who stop at a target parity; and (2) mean completed fertility among those who do not. Applied to Demographic and Health Survey data from women aged 45-49 in 84 low- and middle-income countries, and to United States Census cohorts, the model shows considerable variation in the proportion stopping at specific parities (1-84 per cent). The estimates also show that declines in completed fertility are largely attributable to women who do not stop at target parities, suggesting that stopping at ideal parities may be less important than parity-independent decisions for a wide range of fertility transitions.

Learning from failures of protocol in cross-cultural research.

The many tools that social and behavioral scientists use to gather data from their fellow humans have, in most cases, been honed on a rarefied subset of humanity: highly educated participants with unique capacities, experiences, motivations, and social expectations. Through this honing process, researchers have developed protocols that extract information from these participants with great efficiency. However, as researchers reach out to broader populations, it is unclear whether these highly refined protocols are robust to cultural differences in skills, motivations, and expected modes of social interaction. In this paper, we illustrate the kinds of mismatches that can arise when using these highly refined protocols with nontypical populations by describing our experience translating an apparently simple social discounting protocol to work in rural Bangladesh. Multiple rounds of piloting and revision revealed a number of tacit assumptions about how participants should perceive, understand, and respond to key elements of the protocol. These included facility with numbers, letters, abstract number lines, and 2D geometric shapes, and the treatment of decisions as a series of isolated events. Through on-the-ground observation and a collaborative refinement process, we developed a protocol that worked both in Bangladesh and among US college students. More systematic study of the process of adapting common protocols to new contexts will provide valuable information about the range of skills, motivations, and modes of interaction that participants bring to studies as we develop a more diverse and inclusive social and behavioral science.

Warmth, competence, and closeness may provide more empirically grounded starts for a theory of sentiments.

Gervais & Fessler dissect the folk concept of "contempt" to argue for a functionally integrated model of attitudes and emotions in the context of social relationships. Existing studies of how evaluations of warmth, competence, and closeness shape people's reactions and behaviors towards others may help in operationalizing and testing the proposed model.

Material wealth in 3D: Mapping multiple paths to prosperity in low- and middle- income countries.

Material wealth is a key factor shaping human development and well-being. Every year, hundreds of studies in social science and policy fields assess material wealth in low- and middle-income countries assuming that there is a single dimension by which households can move from poverty to prosperity. However, a one-dimensional model may miss important kinds of prosperity, particularly in countries where traditional subsistence-based livelihoods coexist with modern cash economies. Using multiple correspondence analysis to analyze representative household data from six countries-Nepal, Bangladesh, Ethiopia, Kenya, Tanzania and Guatemala-across three world regions, we identify a number of independent dimension of wealth, each with a clear link to locally relevant pathways to success in cash and agricultural economies. In all cases, the first dimension identified by this approach replicates standard one-dimensional estimates and captures success in cash economies. The novel dimensions we identify reflect success in different agricultural sectors and are independently associated with key benchmarks of food security and human growth, such as adult body mass index and child height. The multidimensional models of wealth we describe here provide new opportunities for examining the causes and consequences of wealth inequality that go beyond success in cash economies, for tracing the emergence of hybrid pathways to prosperity, and for assessing how these different pathways to economic success carry different health risks and social opportunities.

Testing ecological and universal models of body shape and child health using a global sample of infants and young children.

AIM: To test whether a risk of child illness is best predicted by deviations from a population-specific growth distribution or a universal growth distribution. SUBJECTS AND METHODS: Child weight for height and child illness data from 433 776 children (1-59 months) from 47 different low and lower income countries are used in regression models to estimate for each country the child basal weight for height. This study assesses the extent to which individuals within populations deviate from their basal slenderness. It uses correlation and regression techniques to estimate the relationship between child illness (diarrhoea, fever or cough) and basal weight for height, and residual weight for height. RESULTS: In bivariate tests, basal weight for height z-score did not predict the country level prevalence of child illness (r2 = -0.01, n = 47, p = 0.53), but excess weight for height did (r2 = 0.14, p < 0.01). At the individual level, household wealth is negatively associated with the odds that a child is reported as ill (beta = -0.04, p < 0.001, n = 433 776) and basal weight for height was not (beta = 0.20, p = 0.27). Deviations from country-specific basal weight for height were negatively associated with the likelihood of illness (beta = -0.13, p < 0.01), indicating a 13% reduction in illness risk for every 0.1 standard deviation increase in residual weight-for-height Conclusion: These results are consistent with the idea that populations may differ in their body slenderness, and that deviations from this body form may predict the risk of childhood illness.

Anti-fat discrimination in marriage more clearly explains the poverty-obesity paradox.

The target article proposes the insurance hypothesis as an explanation for higher levels of obesity among food-insecure women living in high-income countries. An alternative hypothesis based on anti-fat discrimination in marriage can also account for such correlations between poverty and obesity and is more consistent with finer-grained analyses by marital status, gender, and age.

How does variance in fertility change over the demographic transition?

Most work on the human fertility transition has focused on declines in mean fertility. However, understanding changes in the variance of reproductive outcomes can be equally important for evolutionary questions about the heritability of fertility, individual determinants of fertility and changing patterns of reproductive skew. Here, we document how variance in completed fertility among women (45-49 years) differs across 200 surveys in 72 low- to middle-income countries where fertility transitions are currently in progress at various stages. Nearly all (91%) of samples exhibit variance consistent with a Poisson process of fertility, which places systematic, and often severe, theoretical upper bounds on the proportion of variance that can be attributed to individual differences. In contrast to the pattern of total variance, these upper bounds increase from high- to mid-fertility samples, then decline again as samples move from mid to low fertility. Notably, the lowest fertility samples often deviate from a Poisson process. This suggests that as populations move to low fertility their reproduction shifts from a rate-based process to a focus on an ideal number of children. We discuss the implications of these findings for predicting completed fertility from individual-level variables.

Estimating the absolute wealth of households.

OBJECTIVE: To estimate the absolute wealth of households using data from demographic and health surveys. METHODS: We developed a new metric, the absolute wealth estimate, based on the rank of each surveyed household according to its material assets and the assumed shape of the distribution of wealth among surveyed households. Using data from 156 demographic and health surveys in 66 countries, we calculated absolute wealth estimates for households. We validated the method by comparing the proportion of households defined as poor using our estimates with published World Bank poverty headcounts. We also compared the accuracy of absolute versus relative wealth estimates for the prediction of anthropometric measures. FINDINGS: The median absolute wealth estimates of 1,403,186 households were 2056 international dollars per capita (interquartile range: 723-6103). The proportion of poor households based on absolute wealth estimates were strongly correlated with World Bank estimates of populations living on less than 2.00 United States dollars per capita per day (R(2) = 0.84). Absolute wealth estimates were better predictors of anthropometric measures than relative wealth indexes. CONCLUSION: Absolute wealth estimates provide new opportunities for comparative research to assess the effects of economic resources on health and human capital, as well as the long-term health consequences of economic change and inequality.

Genetic population structure accounts for contemporary ecogeographic patterns in tropic and subtropic-dwelling humans.

Contemporary human populations conform to ecogeographic predictions that animals will become more compact in cooler climates and less compact in warmer ones. However, it remains unclear to what extent this pattern reflects plastic responses to current environments or genetic differences among populations. Analyzing anthropometric surveys of 232,684 children and adults from across 80 ethnolinguistic groups in sub-Saharan Africa, Asia and the Americas, we confirm that body surface-to-volume correlates with contemporary temperature at magnitudes found in more latitudinally diverse samples (Adj. R2 = 0.14-0.28). However, far more variation in body surface-to-volume is attributable to genetic population structure (Adj. R2 = 0.50-0.74). Moreover, genetic population structure accounts for nearly all of the observed relationship between contemporary temperature and body surface-to-volume among children and adults. Indeed, after controlling for population structure, contemporary temperature accounts for no more than 4% of the variance in body form in these groups. This effect of genetic affinity on body form is also independent of other ecological variables, such as dominant mode of subsistence and household wealth per capita. These findings suggest that the observed fit of human body surface-to-volume with current climate in this sample reflects relatively large effects of existing genetic population structure of contemporary humans compared to plastic response to current environments.

The physiological cost of reproduction for rich and poor across 65 countries.

OBJECTIVES: One of the fundamental tradeoffs posited in life history theory is between storing energy for future reproduction versus spending that energy on current reproduction. However, past studies have shown variable and sometimes contradictory effects of reproduction on energy stores among women. METHODS: To examine how varying economic resources can account for these diverse findings, we applied mixed models to Demographic and Health Survey (DHS) data from 187,848 nulliparous and primiparous women of reproductive age (20-34 years) in 65 countries varying widely in economic resources. Using this approach, we tracked average trajectories of body mass through pregnancy and the post-partum period, and assessed how these trajectories varied by household wealth and breastfeeding. RESULTS: In all four wealth categories, sustained breastfeeding posed a substantial tradeoff with energy stores, reducing post-partum BMI by 0.5 to 1.0 kg m(-2) relative to non-breastfeeding women. However, among the wealthiest households (>6,400 USD per capita), this deficit was buffered substantially by greater pre-partum weight gain (+1.1 kg m(-2) compared to women from the poorest households). CONCLUSION: These findings show how the level of economic resources can systematically and profoundly shape a physiological tradeoff in reproduction, and can help account for past contradictory findings. More broadly, these results illustrate how integrating economic and energetic resources in a common framework can help clarify the apparently disparate weight-related outcomes of fertility in different countries.

Child abuse, disruptive behavior disorders, depression, and salivary cortisol levels among institutionalized and community-residing boys in Mongolia.

INTRODUCTION: Hypothalamic-pituitary-adrenal (HPA) axis activity is related to childhood disruptive behavior disorders and to exposure to abuse and neglect. This study explores the relationship of diurnal salivary cortisol levels with oppositional defiant disorder (ODD) and caregiver attitudes toward physical punishment among boys in Mongolia. METHODS: Salivary cortisol was collected in the home or institution 4 times daily for 4 days from 46 boys, aged 4-10 years, in Ulaanbaatar, Mongolia. Caregivers rated child disruptive behavior symptoms, attitudes toward physical punishment, and community violence exposures. Mixed effects models were used to estimate the association of psychopathology and caregiver attitudes with salivary cortisol levels. RESULTS: Boys meeting criteria for ODD displayed consistently lower diurnal salivary cortisol levels compared to boys without ODD diagnoses. Controlling for ODD diagnosis, boys with depression showed higher cortisol levels throughout the day. No other diagnosis was associated with cortisol levels. Psychiatric diagnosis accounted for 17% of between individual variations in cortisol levels unexplained by the covariates. In a separate model, caregivers' beliefs regarding physical punishment accounted for 11% of between individual differences: boys with caregivers who stated physical punishment was necessary for discipline displayed hypocortisolism. Institutionalization did not associate with cortisol levels. DISCUSSION: Salivary cortisol data from a non-Western naturalistic setting support an association of reduced basal HPA activity with disruptive behavior disorders and caregiver attitudes toward discipline. These findings suggest HPA functioning may be a reflection of or mediate disruptive behavior disorders in children across ethnic and cultural settings.