Hydration in relation to water insecurity, heat index, and lactation status in two small-scale populations in hot-humid and hot-arid environments

Ambient temperature and wet bulb globe temperature outperform heat index in predicting hydration status and heat perception in a semi-arid environment

BACKGROUND

Climate change is increasing temperatures, frequency of heatwaves, and erratic rainfall, which threatens human biology and health, particularly in already extreme environments. Therefore, it is important to understand how environmental heat stress measures are tied to human water needs and thermoregulation under increasingly hot conditions.

AIM

To test how ambient temperature, heat index, and wet bulb globe temperature (WBGT) relate to hydration status and thermal heat perception in a hot, semi-arid environment.

SUBJECTS AND METHODS

Urine samples, perceived heat stress, and anthropometrics were collected among Daasanach semi-nomadic pastoralists (n = 187 children, n = 231 adults) in northern Kenya. Environmental heat stress measures were recorded at sample collection; samples' urine specific gravity (USG) was measured.

RESULTS

Multiple linear and logistic regressions indicate that all environmental heat stress measures were associated with USG, odds of dehydration, and heat perception. Ambient temperature performed marginally better than WBGT, and both performed better than heat index. These associations were stronger among children than adults.

CONCLUSION

In a hot, semi-arid climate, ambient temperature and WBGT accurately predict human water needs and heat stress, with children more vulnerable to dehydration. To mitigate consequences of extreme heat, local bioculturally-appropriate hydration (e.g. tea) and cooling (e.g. shade) strategies should be encouraged.

High wet-bulb temperatures, time allocation, and diurnal patterns of breastfeeding in Bangladeshi fisher-traders

BACKGROUND

Climate change is a growing threat to population health, with dangerous combinations of heat and humidity increasing in frequency, particularly in South Asia. Evidence suggests that high temperatures and heat stress influence breastfeeding behaviour and may lead to suboptimal infant and young child nutrition.

AIM

Few studies have quantified the relationship between ambient heat and breastfeeding. Here we evaluate associations between wet-bulb temperature and daily breastfeeding patterns in a rural community in Bangladesh.

SUBJECTS AND METHODS

We used 23 months of daily time-diary data from 68 maternal-child dyads and regional wet-bulb temperatures to test the hypothesis that increased heat and humidity negatively influence breastfeeding outcomes among Shodagor fisher-traders.

RESULTS

We found that higher wet-bulb temperatures predicted reduced daily breastfeeding time allocation, particularly among fishers, and drove shifts towards increased night-time and decreased mid/late morning feeding. Maternal occupation and the interaction of child age with heat strongly influenced diurnal breastfeeding patterns.

CONCLUSION

These results highlight an important role of maternal work on infants' vulnerability to environmental stress. Dyads' ability to behaviourally compensate for extreme heat may be constrained by extended heatwaves, humidity, and economic circumstances, suggesting that climate change will likely exacerbate heat-related risks to global child health going forward.

Interacting Water Insecurity and Food Insecurity: Recent Advances in Theory and Application

Brewis, Workman et al. (2020) provided a basis for significant subsequent advancement in understanding the interplay between household water insecurity and food insecurity across diverse global contexts. This commentary reflects on the subsequent evolution of research and its application in the 5 years since the study's initial online publication in AJHB, highlighting dynamic mechanisms that link water insecurity and food insecurity and the implications for human health. Newer studies suggest that water insecurity may drive food insecurity more significantly than vice versa, with localized case studies revealing the diversity and complexity of multi-scalar factors that contribute to these relationships. Future research priorities include more refined water insecurity measurement tools and further testing of potential mechanisms in theorized causal pathways linking water insecurity and food insecurity to each other and health outcomes.

Food and Water Insecurity and Functional Disability in Adults

Importance

Evidence from diverse global populations suggests that household food insecurity (HFI) is associated with adult disability, but the association between household water insecurity (HWI) and disability remains understudied. Examinations of the joint association of dual HFI and HWI with disability are lacking.

Objective

To explore independent and joint associations of HFI and HWI with functional disability in Ecuadorian adults.

Design, Setting, and Participants

This cross-sectional study used data from the 2018 Ecuadorian National Health and Nutrition Survey, a nationally representative, population-based survey conducted in Ecuador. The study included adults (aged 18-99 years) with information on sociodemographic characteristics, household food and water security, and functional disability status. Data were collected in 2 waves of the survey, from November 2018 to January 2019 and June to July 2019. Statistical analysis was performed from May to December 2024.

Exposures

HFI, WFI, or both.

Main outcomes and Measures

The primary outcome was self-reported functional disability, assessed using the Washington Group Short Set on Functioning, a tool that uses a set of 6 questions to measure activity limitations.

Results

Among 42 071 participants (mean [SE] age, 48.0 [0.1] years; 31 683 male [75.3%]; 1840 African descendant [4.4%], 5184 Indigenous [12.3%], and 35 047 Mestizo ethnic majority group [83.3%]), most lived in urban areas (26 164 participants [62.2%]). Exposure to HFI only was associated with an increased risk for any functional disability (adjusted relative risk [aRR], 1.44; 95% CI, 1.37-1.52), as well as sensory (aRR, 1.43; 95% CI, 1.35-1.52), physical (aRR, 1.56, 95% CI, 1.42-1.72), and cognitive (aRR, 1.78; 95% CI, 1.61-1.98) disabilities. HWI exposure only was associated with increased risk for any functional disability (aRR, 1.12; 95% CI, 1.06-1.20), as well as sensory (aRR, 1.17; 95% CI, 1.09-1.25), physical (aRR, 1.15; 95% CI, 1.05-1.26), and cognitive (aRR, 1.17; 95% CI, 1.03-1.34) disabilities. Exposure to dual HFI and HWI was associated with a greater increase in risk than HFI or HWI alone of any functional disability (aRR, 1.61; 95% CI, 1.50-1.72), as well as sensory (aRR, 1.65; 95% CI, 1.52-1.79), physical (aRR, 1.72; 95% CI, 1.59-1.87), and cognitive (aRR, 2.01; 95% CI, 1.76-2.29) disabilities.

Conclusion and Relevance

In this study, dual exposure to HFI and HWI was associated with a greater increase in risk of any and specific functional disabilities compared with independent contributions of HFI and HWI alone. These findings highlight the importance of addressing HFI and HWI jointly rather than independently when conducting research on disability and other health outcomes and in designing policies and programs to protect at-risk adults and their households.

Chronic Stress and Severe Water Insecurity During the Historic 2022 Drought in Northern Kenya Were Associated With Inflammation Among Daasanach Seminomadic Pastoralists

OBJECTIVE

Extreme climatic events, like droughts, are increasing in frequency and severity. Droughts disrupt community livelihoods and resources with serious implications for human biology. This study investigated how chronic stress, measured by fingernail cortisol concentration (FCC), and water insecurity status were predictive of C-reactive protein (CRP), a biomarker of inflammation, during a historic drought among Daasanach seminomadic pastoralists.

METHODS

Data were collected at the height of the 2022 drought from 128 Daasanach household heads aged 16-80 years in northern Kenya using household surveys, anthropometric measurements, and dried blood spots to assess CRP levels and fingernails to assess FCC. We employed mixed-effects linear and logistic regression models to examine the relationships between log-transformed FCC, high water insecurity status measured via the Household Water Insecurity Experiences (HWISE ≥ 24) scale, and serum-equivalent CRP (log-transformed and dichotomized at mild, low-grade inflammation ≥ 1 mg/L) adjusted for covariates.

RESULTS

The mean serum-equivalent CRP was 4.1 mg/L and 56.3% of Daasanach adults had at least mild, low-grade inflammation. Linear models indicated that ln(FCC) was positively associated with ln(CRP) (β = 0.56, SE = 0.12; p < 0.001). Further, logistic models demonstrated that ln(FCC) (OR = 2.69, 95% CI: 1.84-3.95; p < 0.001) and high water insecurity (OR = 2.23, 95% CI: 1.34-3.72; p = 0.002) were both associated with greater odds of low-grade inflammation.

CONCLUSION

This study provides evidence for how chronic stress and severe water insecurity may impact inflammation levels among pastoralists during drought. Since inflammation is central to cardiometabolic disease etiology, this is an additional reason to mitigate the negative health impacts of droughts and water insecurity exacerbated by climate change.

Water Insecurity Is Associated with Sugar-Sweetened Beverage Consumption in a Small-Scale Population in Lowland Bolivia Experiencing Lifestyle Changes

BACKGROUND

Emerging evidence indicates water insecurity (WI) is detrimental to nutritional outcomes and dietary choices.

OBJECTIVE

WI experiences were measured alongside market and traditional sugar-sweetened beverage (SSB) consumption in a small-scale society experiencing the early stages of a nutrition transition (ie, lifestyle and dietary changes away from traditional foods) to test how they are associated.

DESIGN

The 12-item Household Water Insecurity Experiences (HWISE) scale was implemented along with a cross-sectional retrospective survey of beverage intake and sociodemographic characteristics across 5 communities at varying distances from a market town.

PARTICIPANTS/SETTING

Participants were Tsimané forager-horticulturalist adults aged 16 years and older (n = 455; 47% were women) in lowland Bolivia from April through May 2019.

MAIN OUTCOME MEASURE

Sugar-sweetened beverage consumption and traditional beverage consumption were measured.

STATISTICAL ANALYSES PERFORMED

Multivariate logistic and Poisson regressions were performed, adjusting for possible confounding variables, including age, gender, income, household water needs, and community residence.

RESULTS

Using logistic regressions, each point higher WI (HWISE) score was associated with 23% (95% CI 1.01 to 1.50; P = .035) and 27% (95% CI 1.06 to 1.52; P = .008) higher odds of consuming an SSB in the past week for men and women, respectively. For men, each point higher HWISE score was associated with 13% (95% CI 1.10 to 1.16; P < .001) higher odds of drinking chicha fuerte (ie, a traditional, homemade fermented beverage with antibacterial properties) and 16% (95% CI 1.02 to 1.32; P = .022) higher odds of consuming liquor. SSB consumption was highest in the closest communities to the market town and declined significantly with distance; and traditional beverages, such as chicha dulce (a sugar-sweetened, unfermented homemade chicha), were lowest in the close communities and increased with distance to the market town.

CONCLUSIONS

Among Tsimané adults living in the Bolivian Amazon experiencing the nutrition transition, WI was associated with greater SSB intake. Distance to the main market town shaped access and preferences, as it was associated with SSB and traditional beverage consumption.

Recent Research on the Human Biology of Pastoralists

Despite encroachment by agricultural systems and globalization, pastoral nomads maintain a robust presence in terms of numbers and subsistence activity. At the same time, increasing concern about climate change has promoted awareness that increased climatic fluctuation may push pastoral population past their capacity for resilience. The response of pastoralists to climate change has important implications for our evolutionary past and our increasingly problematic future. Yet, pastoralists have received less explicit attention than foragers as populations under consistent selective constraints including limited caloric intake, high levels of habitual activity, and high disease burdens. Additional factors include exposure to cold and high temperatures, as well as high altitude. Over the last 20 or so years, the use of new techniques for measuring energetics, including actigraphs and doubly labeled water have built on existing noninvasive sample collection for hormones, immune markers and genes to provide a more detailed picture of the human biology of pastoral populations. Here I consider recent work on pastoralists from Siberia and northern Europe, Africa, Asia, and South America. I survey what is known about maternal milk composition and infant health, childhood growth, lactase persistence, and adult energy expenditure and lactase persistence to build a picture of the pastoralist biological response to environmental conditions, including heat, cold, and high altitude. Where available I include information about population history because of its importance for selection. I end by outlining the impact of milk consumption and climate over the human life cycle and make suggestions for further research.

Physical Activity and Pregnancy Norms Among Daasanach Semi-Nomadic Pastoralist Women in Northern Kenya

OBJECTIVES

In subsistence populations, high physical activity is typically maintained throughout pregnancy. Market integration shifts activity patterns to resemble industrialized populations, with more time allocated to sedentary behavior. Daasanach semi-nomadic pastoralists living in northern Kenya face lifestyle heterogeneity due to the emergence of a market center. We investigate how Daasanach women manage the energetic demands of pregnancy with subsistence labor tasks and how market integration relates to variation in energetic demands, physical activity, and coping strategies.

METHODS

We conducted nine focus group discussions with 72 pregnant women. We also deployed wrist-worn fitness trackers with 21 pregnant women in two community types: central or peripheral to the market center to capture variation in market integration. Data from focus group discussions were analyzed using thematic analysis. We used multiple linear regression to examine the relationship between gestational age and physical activity.

RESULTS

We identified themes of increased fatigue, diet restrictions, and assistance with labor tasks during pregnancy. Gestational age negatively predicted mean daily steps, with a decrease of 1160 ± 437 steps per day with each consecutive pregnancy month. Stratified by community type, gestational age only negatively predicted mean daily steps for peripheral communities, with a decrease of 1443 ± 629 steps per day with each consecutive pregnancy month.

CONCLUSIONS

Results suggest that physical activity differs with market integration early, but not late, in pregnancy. Daasanach women cope with the energetic demands of pregnancy by reducing physical activity late in pregnancy and receiving assistance with labor tasks from family and neighbors.

Water insecurity may exacerbate food insecurity even in water-rich environments: Evidence from the Bolivian Amazon

Globally, challenges with water and food are two of the most pressing problems people face. Yet hydrologically water-rich environments and rural environments are often overlooked in these discussions due to abundance of natural water resources. Here we test the relationship between water and food insecurity among 270 Tsimane' households in the Bolivian Amazon. Water challenges were evaluated with the Household Water Insecurity Experiences Scale (HWISE), water quality perception, objective water quality analyses, and water access via the JMP drinking water ladder. Food insecurity was measured with the Household Food Insecurity Access Scale (HFIAS), and quantitative measures of food frequency recall were used to further test the water and food insecurity relationship. Using multilevel mixed-effects linear regression, each point increase in HWISE score was associated with 0.47 point (95 % CI: 0.30, 0.62, p < 0.001) higher food insecurity, and households with access to improved water sources had between 1.25 and 1.36 points (95 % CI: -2.61, -0.01, p < 0.05) lower food insecurity compared to households reliant on surface water. These relationships held true independent of quantitative measures of both fish and meat consumption. Using mixed-effects logistic regression analyses, each point increase in HWISE score was associated with 43 % (95 % CI: 1.25-1.66, p < 0.001) increased odds of experiencing severe food insecurity. Households changing what was eaten due to experienced water problems was associated with 2.33 points (95 % CI: 0.41, 4.25, p < 0.05) higher food insecurity. This relationship held true independent of perceived water quality, indicating other structural water problems may be important here in the household water and food insecurity relationship. These results demonstrate that even in water-rich environments, like the Amazon, water and food insecurity are interconnected. Further, despite the challenging conditions, equitable structural interventions, like the development of improved water infrastructure, are critical for the provision of clean drinking water and may simultaneously help alleviate food insecurity.

Mobility ideation due to water problems during historic 2022 drought associated with livestock wealth, water and food insecurity, and fingernail cortisol concentration in northern Kenya

Climate change is triggering environmental mobility through chronic water problems and punctuated events. Thinking about moving locations, or "mobility ideation", is the precursor to migration intentionality and actual migration. Drawing on the embodiment construct, this study examines how the worst drought in recent history in the Horn of Africa affected water-related mobility ideation and, in turn, fingernail cortisol concentration (FCC), a chronic stress biomarker, among Daasanach semi-nomadic pastoralists in northern Kenya. To address these questions, we primarily draw on survey, anthropometric, water quality, and biomarker data among 175 adults living in seven communities in 2022. We used mixed-effects ordered logistic regression to test how livestock wealth, water insecurity, food insecurity, and anxiety/depression symptom scores were associated with household mobility ideation. We then used generalized linear models to test the association between mobility ideation on FCC. Thinking about moving at least once due to water problems increased from pre-drought in 2019 (55%) to during the drought in 2022 (92%), while actual mobility declined. Livestock wealth, while associated with actual mobility in the prior year, was protective against increased mobility ideation, while water insecurity, food insecurity, and anxiety/depression symptoms were associated with greater odds of thinking of leaving in 2022. Compared to adults who did not consider moving, those who considered moving rarely, sometimes, and often had FCC levels 18.1% higher (95% CI, 1.01-1.38; p = 0.039), 19.4% higher (1.01-1.41; p = 0.040), and 32.3% higher (1.01-1.73; p = 0.039), respectively, with results consistent in sensitivity analyses. Extreme climatic events in water scarce regions may increase mobility ideation through worsened experiential indicators of well-being and resource insecurity. Mobility ideation may capture measures of adversity suffered by pastoralists and signify climate distress. This research broadens understanding of how droughts get under the skin by leading to resource insecurity and triggering thoughts of moving, which increases chronic stress.

Coping with extreme heat: current exposure and implications for the future

A preview of how effective behavioral, biological and technological responses might be in the future, when outdoor conditions will be at least 2°C hotter than current levels, is available today from studies of individuals already living in extreme heat. In areas where high temperatures are common-particularly those in the hot and humid tropics-several studies report that indoor temperatures in low-income housing can be significantly hotter than those outdoors. A case study indicates that daily indoor heat indexes in almost all the 123 slum dwellings monitored in Kolkata during the summer were above 41°C (106°F) for at least an hour. Economic constraints make it unlikely that technological fixes, such as air conditioners, will remedy conditions like these-now or in the future. People without access to air conditioning will have to rely on behavioral adjustments and/or biological/physiological acclimatization. One important unknown is whether individuals who have lived their entire lives in hot environments without air conditioning possess natural levels of acclimatization greater than those indicated by controlled laboratory studies. Answering questions about the future will require more studies of heat conditions experienced by individuals, more information on indoor versus outdoor heat conditions, and a greater understanding of the behavioral and biological adjustments made by people living today in extremely hot conditions.

Total daily energy expenditure and elevated water turnover in a small-scale semi-nomadic pastoralist society from Northern Kenya

BACKGROUND

Pastoralists live in challenging environments, which may be accompanied by unique activity, energy, and water requirements.

AIM

Few studies have examined whether the demands of pastoralism contribute to differences in total energy expenditure (TEE) and water turnover (WT) compared to other lifestyles.

SUBJECTS AND METHODS

Accelerometer-derived physical activity, doubly labelled water-derived TEE and WT, and anthropometric data were collected for 34 semi-nomadic Daasanach adults from three northern Kenyan communities with different levels of pastoralist activity. Daasanach TEEs and WTs were compared to those of other small-scale and industrialised populations.

RESULTS

When modelled as a function of fat-free-mass, fat-mass, age, and sex, TEE did not differ between Daasanach communities. Daasanach TEE (1564-4172 kcal/day) was not significantly correlated with activity and 91% of TEEs were within the range expected for individuals from comparison populations. Mean WT did not differ between Daasanach communities; Daasanach absolute (7.54 litres/day men; 7.46 litres/day women), mass-adjusted, and TEE-adjusted WT was higher than most populations worldwide.

CONCLUSIONS

The similar mass-adjusted TEE of Daasanach and industrialised populations supports the hypothesis that habitual TEE is constrained, with physically demanding lifestyles necessitating trade-offs in energy allocation. Elevated WT in the absence of elevated TEE likely reflects a demanding active lifestyle in a hot, arid climate.

The effects of lifestyle change on indicators of cardiometabolic health in semi-nomadic pastoralists

Background and objectives

Non-communicable disease risk and the epidemic of cardiometabolic diseases continue to grow across the expanding industrialized world. Probing the relationships between evolved human physiology and modern socioecological conditions is central to understanding this health crisis. Therefore, we investigated the relationships between increased market access, shifting subsistence patterns and cardiometabolic health indicators within Daasanach semi-nomadic pastoralists who vary in their engagement in traditional lifestyle and emerging market behaviors.

Methodology

We conducted cross-sectional socioecological, demographic and lifestyle stressor surveys along with health, biomarker and nutrition examinations among 225 (51.6% female) Daasanach adults in 2019-2020. We used linear mixed-effects models to test how differing levels of engagement in market integration and traditional subsistence activities related to blood pressure (BP), body composition and blood chemistry.

Results

We found that systolic and diastolic BP, as well as the probability of having high BP (hypertension), were negatively associated with distance to market, a proxy for market integration. Additionally, body composition varied significantly by socioeconomic status (SES), with significant positive associations between BMI and body fat and higher SES among adults.

Conclusions and implications

While evidence for evolutionary mismatch and health variation have been found across a number of populations affected by an urban/rural divide, these results demonstrate the effects of market integration and sedentarization on cardiometabolic health associated with the early stages of lifestyle changes. Our findings provide evidence for the changes in health when small-scale populations begin the processes of sedentarization and market integration that result from myriad market pressures.

Early childhood growth in Daasanach pastoralists of Northern Kenya: Distinct patterns of faltering in linear growth and weight gain

OBJECTIVES

Investigations of early childhood growth among small-scale populations are essential for understanding human life history variation and enhancing the ability to serve such communities through global public health initiatives. This study characterizes early childhood growth trajectories and identifies differences in growth patterns relative to international references among Daasanach semi-nomadic pastoralist children living in a hot, arid region of northern Kenya.

METHODS

A large sample of height and weight measures were collected from children (N = 1756; total observations = 4508; age = 0-5 years) between 2018 and 2020. Daasanach growth was compared to international reference standards and Daasanach-specific centile growth curves and pseudo-velocity models were generated using generalized additive models for location scale and size.

RESULTS

Compared to World Health Organization (WHO) reference, relatively few Daasanach children were stunted (14.3%), while a large proportion were underweight (38.5%) and wasted (53.6%). Additionally, Daasanach children had a distinctive pattern of growth, marked by an increase in linear growth velocity after 24 months of age and relatively high linear growth velocity throughout the rest of early childhood.

CONCLUSIONS

These results identify a unique pattern of early childhood growth faltering among children in a small-scale population and may reflect a thermoregulatory adaptation to their hot, arid environment. As linear growth and weight gain remain important indicators of health, the results of this study provide insight into growth velocity variations. This study has important implications for global public health efforts to identify and address sources of early growth faltering and undernutrition in small-scale populations.

When the flood passes, does health return? A short panel examining water and food insecurity, nutrition, and disease after an extreme flood in lowland Bolivia

OBJECTIVES

Flooding is the most frequent extreme-weather disaster and disproportionately burdens marginalized populations. This article examines how food and water insecurity, blood pressure (BP), nutritional status, and diarrheal and respiratory illnesses changed during the 2 months following a historic flood in lowland Bolivia.

METHODS

Drawing on longitudinal data from Tsimane' forager-horticulturalist (n = 118 household heads; n = 129 children) directly after a historic 2014 flood and ~2 months later, we use fixed effects linear regression and random effects logistic regression models to test changes in the markers of well-being and health over the recovery process.

RESULTS

Results demonstrated that water insecurity scores decreased significantly 2 month's postflood, while food insecurity scores remained high. Adults' systolic and diastolic BP significantly declined 2 months after the flood's conclusion. Adults experienced losses in measures of adiposity (BMI, sum of four skinfolds, waist circumference). Children gained weight and BMI-for-age Z-scores indicating buffering of children by adults from food stress that mainly occurred in the community closer to the main market town with greater access to food aid. Odds of diarrhea showed a nonsignificant decline, while cough increased significantly for both children and adults 2 months postflood.

CONCLUSIONS

Water insecurity and BP improved during the recovery process, while high levels of food insecurity persisted, and nutritional stress and respiratory illness worsened. Not all indicators of well-being and health recover at the same rate after historic flooding events. Planning for multiphase recovery is critical to improve health of marginalized populations after flooding.

Extreme climatic events and human biology and health: A primer and opportunities for future research

Extreme climatic events are increasing in frequency, leading to hotter temperatures, flooding, droughts, severe storms, and rising oceans. This special issue brings together a collection of seven articles that describe the impacts of extreme climatic events on a diverse set of human biology and health outcomes. The first two articles cover extreme temperatures extending from extreme heat to cold and changes in winter weather and the respective implications for adverse health events, human environmental limits, well-being, and human adaptability. Next, two articles cover the effects of exposures to extreme storms through an examination of hurricanes and cyclones on stress and birth outcomes. The following two articles describe the effects of extreme flooding events on livelihoods, nutrition, water and food insecurity, diarrheal and respiratory health, and stress. The last article examines the effects of drought on diet and food insecurity. Following a brief review of each extreme climatic event and articles covered in this special issue, I discuss future research opportunities-highlighting domains of climate change and specific research questions that are ripe for biological anthropologists to investigate. I close with a description of interdisciplinary methods to assess climate exposures and human biology outcomes to aid the investigation of the defining question of our time - how climate change will affect human biology and health. Ultimately, climate change is a water, food, and health problem. Human biologists offer a unique perspective for a combination of theoretical, methodological, and applied reasons and thus are in a prime position to contribute to this critical research agenda.

Growth and growth trajectory among infants in early life: contributions of food insecurity and water insecurity in rural Zimbabwe

Introduction

Stunting or linear growth faltering, measured by length-for-age Z-score (LAZ), remains a significant public health challenge, particularly in rural low-income and middle-income countries. It is a marker of inadequate environments in which infants are born and raised. However, the contributions of household resource insecurities, such as food and water, to growth and growth trajectory are understudied.

Methods

We used the cluster-randomised Sanitation Hygiene and Infant Nutrition Efficacy trial to determine the association of household-level food insecurity (FI) and water insecurity (WI) on LAZ and LAZ trajectory among infants during early life. Dimensions of FI (poor access, household shocks, low availability and quality) and WI (poor access, poor quality, low reliability) were assessed with the multidimensional household food insecurity and the multidimensional household water insecurity measures. Infant length was converted to LAZ based on the 2006 WHO Child Growth Standards. We report the FI and WI fixed effects from multivariable growth curve models with repeated measures of LAZ at 1, 3, 6, 12 and 18 months (M1-M18).

Results

A total of 714 and 710 infants were included in our analyses of LAZ from M1 to M18 and M6 to M18, respectively. Mean LAZ values at each time indicated worsening linear growth. From M1 to M18, low food availability and quality was associated with lower LAZ (β=-0.09; 95% -0.19 to -0.13). From M6 to M18, poor food access was associated with lower LAZ (β=-0.11; 95% -0.20 to -0.03). None of the WI dimensions were associated with LAZ, nor with LAZ trajectory over time.

Conclusion

FI, but not WI, was associated with poor linear growth among rural Zimbabwean infants. Specifically, low food availability and quality and poor food access was associated with lower LAZ. There is no evidence of an effect of FI or WI on LAZ trajectory.

Toolkit article: Approaches to measuring social inequities in health in human biology research

Across populations, human morbidity and mortality risks generally follow clear gradients, with socially-disadvantaged individuals and groups tending to have higher morbidity and mortality at all life stages relative to those more socially advantaged. Anthropologists specialize in understanding the proximate and ultimate factors that shape variation in human biological functioning and health and are therefore well-situated to explore the relationships between social position and health in diverse ecological and cultural contexts. While human biologists have developed sophisticated methods for assessing health using minimally-invasive methods, at a disciplinary level, we have room for conceptual and methodological improvement in how we frame, measure, and analyze the social inequities that might shape health inequities. This toolkit paper elaborates on some steps human biologists should take to enhance the quality of our research on health inequities. Specifically, we address: (1) how to frame unequal health outcomes (i.e., inequalities vs. disparities vs. inequities) and the importance of identifying our conceptual models of how these inequities emerge; (2) how to measure various axes of social inequities across diverse cultural contexts, and (3) approaches to community collaboration and dissemination. We end by discussing (4) future directions in human biology research of health inequities, including understanding the ultimate causes of sensitivity to social inequities and transitioning from research to action.

Water Insecurity, Water Borrowing, and Psychosocial Stress Among Daasanach Pastoralists in Northern Kenya

This article quantifies Daasanach water insecurity experiences in Northern Kenya, examines how water insecurity is associated with water borrowing and psychosocial stress, and evaluates if water borrowing mitigates the stress from water insecurity. Of 133 households interviewed in 7 communities, 94% were water insecure and 74.4% borrowed water three or more times in the prior month. Regression analyses demonstrate water borrowing frequency moderates the relationship between water insecurity and psychosocial stress. Only those who rarely or never borrowed water reported greater stress with higher water insecurity. The coping mechanism of water borrowing may help blunt water insecurity-related stress.

Cross-cultural variation in thirst perception in hot-humid and hot-arid environments: Evidence from two small-scale populations

OBJECTIVES

Thirst is an evolved central homeostatic feedback system that helps regulate body water for survival. Little research has examined how early development and exposure to extreme environments and water availability affect thirst perception, particularly outside Western settings. Therefore, we compared two indicators of perceived thirst (current thirst and pleasantness of drinking water) using visual scales among Tsimane' forager-horticulturalists in the hot-humid Bolivian Amazon and Daasanach agro-pastoralists in hot-arid Northern Kenya.

METHODS

We examined how these measures of perceived thirst were associated with hydration status (urine specific gravity), ambient temperatures, birth season, age, and population-specific characteristics for 607 adults (n = 378 Tsimane', n = 229 Daasanach) aged 18+ using multi-level mixed-effect regressions.

RESULTS

Tsimane' had higher perceived thirst than Daasanach. Across populations, hydration status was unrelated to both measures of thirst. There was a significant interaction between birth season and temperature on pleasantness of drinking water, driven by Kenya data. Daasanach born in the wet season (in utero during less water availability) had blunted pleasantness of drinking water at higher temperatures compared to those born in the dry season (in utero during greater water availability).

CONCLUSIONS

Our findings suggest hydration status is not a reliable predictor of thirst perceptions in extreme-hot environments with ad libitum drinking. Rather, our findings, which require additional confirmation, point to the importance of water availability during gestation in affecting thirst sensitivity to heat and water feedback mechanisms, particularly in arid environments. Thirst regulation will be increasingly important to understand given climate change driven exposures to extreme heat and water insecurity.

Using Water Intake Dietary Recall Data to Provide a Window into US Water Insecurity

BACKGROUND

In the United States, problems with the provision of safe, affordable water have resulted in an increasing number of adults who avoid their tap water, which could indicate underlying water insecurity. Dietary recalls provide critical nutritional surveillance data, yet have been underexplored as a water insecurity monitoring tool.

OBJECTIVES

This article aims to demonstrate how water intake variables from dietary recall data relate to and predict a key water insecurity proxy, that is, tap water avoidance.

METHODS

Using 2005-2018 NHANES data from 32,329 adults, I examine distributions and trends of mean intakes of total, plain (sum of tap and bottled water), tap, and bottled water, and percentage consuming no tap and exclusive bottled water. Second, I use multiple linear and logistic regressions to test how tap water avoidance relates to plain water intake and sugar-sweetened beverage (SSB) consumption. Next, I use receiver operating characteristics (ROC) curves to test the predictive accuracy of no plain water, no tap, and exclusive bottled water intake, and varying percentages of plain water consumed from tap water compared with tap water avoidance.

RESULTS

Trends indicate increasing plain water intake between 2005 and 2018, driven by increasing bottled water intake. In 2017-18, 51.4% of adults did not drink tap water on a given day, whereas 35.8% exclusively consumed bottled water. Adults who avoided their tap water consumed less tap and plain water, and significantly more bottled water and SSBs on a given day. No tap intake and categories of tap water intake produced 77% and 78% areas under the ROC curve in predicting tap water avoidance.

CONCLUSIONS

This study demonstrates that water intake variables from dietary recalls can be used to accurately predict tap water avoidance and provide a window into water insecurity. Growing reliance on bottled water could indicate increasing concerns about tap water.

Drinking frequency in wild lactating chimpanzees (Pan troglodytes schweinfurthii) and their offspring

Maintaining water balance is essential for organismal health, and lactating females must balance individual needs with milk production and offspring hydration. Primate milk is dilute and presumed to be the primary source for infant hydration for a considerable time period. Few studies have investigated the hydration burden that lactation may place on female primates. In this study, we investigated sources of variation in female and offspring drinking frequency among wild chimpanzees (Pan troglodytes). We hypothesized females would experience seasonal and lactation hydration burdens and adjust their drinking behavior to accommodate these, but this hydration burden would vary between females of different dominance ranks. We also predicted that parity would relate to maternal drinking frequency since primiparous females are still investing in their own growth. Finally, we predicted that offspring would drink more in the dry season and as they aged and lost milk as a water source, but that offspring of high-ranking females would be buffered from these effects. Using 41 years of long-term data on the behavior of mothers and offspring of Gombe National Park, we found that mothers drank more in the dry season, but there was no significant difference between mothers of different ranks during this period. Low-ranking females drank significantly more than mid- and high-ranking females during late lactation. Offspring also drank more in the dry season and as they aged, but there was no evidence of buffering for those with high-ranking mothers. While chimpanzees in our study population drank infrequently, they do demonstrate noticeable shifts in drinking behavior that suggests seasonal and reproductive hydration burdens.

The embodiment of water insecurity: Injuries and chronic stress in lowland Bolivia

Water is critical to health and wellbeing. Studies have theorized that problems with water can become embodied, yet few studies have quantified this. Therefore, we first sought to understand the lowland Bolivian water environment of Tsimane' forager-horticulturalists. We assessed the water environment holistically, using objective measures of water quality and water services (Joint Monitoring Programme's drinking water services ladder) and subjective measures, including perceived water safety and water insecurity experiences [Household Water Insecurity Experiences Scale (HWISE)]. We tested how water service levels, perceived water safety, and water fetching frequency were associated with HWISE scores using Tobit regression models among 270 households. We then tested if and how water becomes embodied via self-reported water-related injury and a chronic stress biomarker, hair cortisol concentration (HCC). Results demonstrated that, compared with households using surface water, households with basic water services had HWISE scores 1.59-pts lower (SE = 0.29; P < 0.001). Ingestion of water perceived to be "bad" and more daily water-fetching trips were associated with higher HWISE scores. Twenty percent of households reported prior water-related injuries, with women most commonly injured. In logistic regressions, each point higher HWISE score was associated with 28% (95%CI:1.16-1.41; P < 0.001) higher odds of injury. Basic water services compared to surface water was associated with 48% lower odds (OR = 0.52; 95%CI:0.33-0.82; P = 0.005) of injury. Finally, using linear regressions among 332 adults, HWISE scores were not associated with HCC. Past water-related injury was associated with higher HCC (Beta = 0.31; SE = 0.09; P = 0.029) among women, but not men. Relying on unimproved water services compared to surface was associated with 46.2% higher HCC for women (Beta=0.38; SE=0.14; P=0.048) and 55.3% higher HCC for men (Beta=0.44; SE=0.15; P=0.044), respectively. Overall, our findings demonstrate that water insecurity can become embodied through water-related injuries and elevated HCC. Improving water service levels through an equity lens may help ameliorate water insecurity and its accompanying negative health effects.

Interactions between climate change and infrastructure projects in changing water resources: An ethnobiological perspective from the Daasanach, Kenya

The fast and widespread environmental changes that have intensified in the last decades are bringing disproportionate impacts to Indigenous Peoples and Local Communities. Changes that affect water resources are particularly relevant for subsistence-based peoples, many of whom already suffer from constraints regarding reliable access to safe water. Particularly in areas where water is scarce, climate change is expected to amplify existing stresses in water availability, which are also exacerbated by multiple socioeconomic drivers. In this paper, we look into the local perceptions of environmental change expressed by the Daasanach people of northern Kenya, where the impacts of climate change overlap with those brought by large infrastructure projects recently established in the Omo River. We show that the Daasanach have rich and detailed understanding of changes in their environment, especially in relation to water resources. Daasanach understand observations of change in different elements of the social-ecological system as an outcome of complex interactions between climatic and non-climatic drivers of change. Our findings highlight the perceived synergistic effects of climate change and infrastructure projects in water resources, driving multiple and cascading impacts on biophysical elements and local livelihoods. Our results also demonstrate the potential of Local Ecological Knowledge in enhancing the understanding of complex social-ecological issues, such as the impacts of environmental change in local communities. To minimize and mitigate the social-ecological impacts of development projects, it is essential to consider potential synergies between climatic and socioeconomic factors and to ensure inclusive governance rooted in local understandings of environmental change.

Heat Safety in the Workplace: Modified Delphi Consensus to Establish Strategies and Resources to Protect the US Workers

The purpose of this consensus document was to develop feasible, evidence-based occupational heat safety recommendations to protect the US workers that experience heat stress. Heat safety recommendations were created to protect worker health and to avoid productivity losses associated with occupational heat stress. Recommendations were tailored to be utilized by safety managers, industrial hygienists, and the employers who bear responsibility for implementing heat safety plans. An interdisciplinary roundtable comprised of 51 experts was assembled to create a narrative review summarizing current data and gaps in knowledge within eight heat safety topics: (a) heat hygiene, (b) hydration, (c) heat acclimatization, (d) environmental monitoring, (e) physiological monitoring, (f) body cooling, (g) textiles and personal protective gear, and (h) emergency action plan implementation. The consensus-based recommendations for each topic were created using the Delphi method and evaluated based on scientific evidence, feasibility, and clarity. The current document presents 40 occupational heat safety recommendations across all eight topics. Establishing these recommendations will help organizations and employers create effective heat safety plans for their workplaces, address factors that limit the implementation of heat safety best-practices and protect worker health and productivity.

Perspective: The Importance of Water Security for Ensuring Food Security, Good Nutrition, and Well-being

Water security is a powerful concept that is still in its early days in the field of nutrition. Given the prevalence and severity of water issues and the many interconnections between water and nutrition, we argue that water security deserves attention commensurate with its importance to human nutrition and health. To this end, we first give a brief introduction to water insecurity and discuss its conceptualization in terms of availability, access, use, and stability. We then lay out the empirical grounding for its assessment. Parallels to the food-security literature are drawn throughout, both because the concepts are analogous and food security is familiar to the nutrition community. Specifically, we review the evolution of scales to measure water and food security and compare select characteristics. We then review the burgeoning evidence for the causes and consequences of water insecurity and conclude with 4 recommendations: 1) collect more water-insecurity data (i.e., on prevalence, causes, consequences, and intervention impacts); 2) collect better data on water insecurity (i.e., measure it concurrently with food security and other nutritional indicators, measure intrahousehold variation, and establish baseline indicators of both water and nutrition before interventions are implemented); 3) consider food and water issues jointly in policy and practice (e.g., establish linkages and possibilities for joint interventions, recognize the environmental footprint of nutritional guidelines, strengthen the nutrition sensitivity of water-management practices, and use experience-based scales for improving governance and regulation across food and water systems); and 4) make findings easily available so that they can be used by the media, community organizations, and other scientists for advocacy and in governance (e.g., tracking progress towards development goals and holding implementers accountable). As recognition of the importance of water security grows, we hope that so too will the prioritization of water in nutrition research, funding, and policy.

Household Water and Food Insecurity Are Positively Associated with Poor Mental and Physical Health among Adults Living with HIV in Western Kenya

BACKGROUND

Household food insecurity (FI) and water insecurity (WI) are prevalent public health issues that can co-occur. Few studies have concurrently assessed their associations with health outcomes, particularly among people living with HIV.

OBJECTIVES

We aimed to investigate the associations between FI and WI and how they relate to physical and mental health.

METHODS

Food-insecure adult smallholder farmers living with HIV in western Kenya were recruited to participate in a cluster-randomized controlled trial of a multisectoral agricultural and asset loan intervention. We used baseline data on experiences of FI (using the Household Food Insecurity Access Scale, range: 0-27) and WI (using a modified scale developed for this region, range: 0-51) in the prior month (n = 716). Outcomes included probable depression (using the Hopkins Symptom Checklist), fatigue and diarrhea in the prior month, and overall mental and physical health (using the Medical Outcomes Study HIV Health Survey, range: 0-100). We first assessed Pearson correlations between FI, WI, and sociodemographic characteristics. We then developed 3 regressions for each health outcome (control variables and FI; control variables and WI; control variables, FI, and WI) and compared model fit indexes.

RESULTS

Correlations between household FI, WI, and wealth were low, meaning they measure distinct constructs. FI and WI were associated with numerous physical and mental health outcomes; accounting for both resource insecurities typically provided the best model fit. For instance, when controlling for FI, each 10-point higher WI score was associated with a 6.42-point lower physical health score (P < 0.001) and 2.92 times greater odds of probable depression (P < 0.001).

CONCLUSIONS

Assessing both FI and WI is important for correctly estimating their relation with health outcomes. Interventions that address food- and water-related issues among persons living with HIV concurrently will likely be more effective at improving health than those addressing a single resource insecurity. This trial was registered at clinicaltrials.gov as NCT02815579.

Drinking water salinity is associated with hypertension and hyperdilute urine among Daasanach pastoralists in Northern Kenya

Water salinity is a growing global environmental health concern. However, little is known about the relation between water salinity and chronic health outcomes in non-coastal, lean populations. Daasanach pastoralists living in northern Kenya traditionally rely on milk, yet are experiencing socioecological changes and have expressed concerns about the saltiness of their drinking water. Therefore, this cross-sectional study conducted water quality analyses to examine how water salinity, along with lifestyle factors like milk intake, was associated with hypertension (blood pressure BP ≥140 mm Hg systolic or ≥90 mm Hg diastolic) and hyperdilute urine (urine specific gravity <1.003 g/mL, indicative of altered kidney function). We collected health biomarkers and survey data from 226 non-pregnant adults (46.9% male) aged 18+ from 134 households in 2019 along with participant observations in 2020. The salinity (total concentration of all dissolved salts) of reported drinking water from hand-dug wells in dry river beds, boreholes, and a pond ranged from 120 to 520 mg/L. Water from Lake Turkana and standpipes, which was only periodically used for consumption when no other drinking sources are available, ranged from 1100 to 2300 mg/L. Multiple logistic regression models with standard errors clustered on households indicate that each additional 100 mg/L of drinking water salinity was associated with 45% (95% CI: 1.09-1.93, P = 0.010) increased odds of hypertension and 33% (95% CI: 0.97-1.83, P = 0.075) increased odds of hyperdilute urine adjusted for confounders. Results were robust to multiple specifications of the models and sensitivity analyses. Daily milk consumption was associated with 61-63% (P < 0.01) lower odds of both outcomes. This considerable protective effect of milk intake may be due to the high potassium, magnesium, and calcium contents or the protective lifestyle considerations of moving with livestock. Our study results demonstrate that drinking water salinity may have critical health implications for blood pressure and kidney function even among lean, active pastoralists.

Rapidly declining body temperature in a tropical human population

Normal human body temperature (BT) has long been considered to be 37.0°C. Yet, BTs have declined over the past two centuries in the United States, coinciding with reductions in infection and increasing life expectancy. The generality of and reasons behind this phenomenon have not yet been well studied. Here, we show that Bolivian forager-farmers (n = 17,958 observations of 5481 adults age 15+ years) inhabiting a pathogen-rich environment exhibited higher BT when first examined in the early 21st century (~37.0°C). BT subsequently declined by ~0.05°C/year over 16 years of socioeconomic and epidemiological change to ~36.5°C by 2018. As predicted, infections and other lifestyle factors explain variation in BT, but these factors do not account for the temporal declines. Changes in physical activity, body composition, antibiotic usage, and thermal environment are potential causes of the temporal decline.