Conflict or congruence? Maternal and infant-centric factors associated with shorter exclusive breastfeeding durations among the Tsimane

Barriers to healthcare utilization among married women in Afghanistan: the role of asset ownership and women's autonomy

Women face multiple socio-economic, cultural, contextual, and perceived barriers in health service utilization. Moreover, poor autonomy and financial constraints act as crucial factors to their healthcare accessibility. Therefore, the objective of the present study is to study the association between health care utilization barriers and women empowerment, including asset ownership among currently married women in Afghanistan. Data of 28,661 currently married women from Afghanistan demographic health survey (2015) was used to carry out this study. Barriers to access healthcare were computed based on problems related to permission, money, distance, and companionship, whereas women empowerment and asset ownership were computed as potential covariates along with other socio-economic risk factors. Bivariate and logistic analysis was carried out to study the association and odds of explanatory variables. Our results confirm the significant and strong association between the barriers to access healthcare and various explanatory variables. Women having any decision-making autonomy are less likely to face any odds [(AOR = 0.56, p < 0.001), CI: 0.51-0.61] among the currently married women than those who don't have any decision-making authority. Similarly, women who justify their beating for some specific reasons face the greater difficulty of accessing health care [(AOR = 1.76, p < 0.001), CI: 1.61-1.93]. In terms of asset ownership, women having any asset ownership (land or household) are less likely to face any barriers in health services utilization given the lower odds [(AOR = 0.91, p < 0.001), CI: 0.90-0.98]. Accessing maternal health is a crucial policy challenge in Afghanistan. A substantial proportion of women face barriers related to approval, money, distance, and companionship while accessing the health services utilization in Afghanistan. Similarly, women empowerment and asset ownership are significantly associated with health service accessibility. This paper therefore suggests for some policy interventions to strengthen the healthcare needs of women and ensure healthcare accessibility by scaling down these potential barriers like poor autonomy, asset ownership and domestic violence.

Variation in maternal lactation practices associated with changes in diurnal maternal inflammation

While the importance of human milk in shaping infant immune function is well established, the impact of at-the-nipple (ATN) breastfeeding on maternal immune status has been understudied. Since lactation evolved to support infant survival and boost maternal fitness, we predict that ATN breastfeeding will confer benefits on maternal immune function. We measure the absolute and relative frequency of different infant feeding methods (ATN breastfeeding, pumping, donated milk, other supplementation) used by postpartum women in Seattle, WA (USA). We implement Bayesian modeling to estimate the effects of ATN breastfeeding on diurnal change in secretion rate of "pro-inflammatory" salivary cytokines and C-reactive protein (CRP). Our results show that most mothers in our sample used a variety of infant feeding methods, with pumping as the most common alternative to ATN breastfeeding. We find that ATN breastfeeding is associated with non-linear effects on diurnal IL-8 and CRP. Furthermore, we find that women who report zero versus ubiquitous ATN breastfeeding exhibit opposing diurnal patterns in CRP secretion rate. This study provides evidence that variation in maternal lactation practices corresponds to differences in maternal immune responses, highlighting how measuring lactation as a continuous variable can further enhance understanding of postpartum maternal physiology.

Apolipoprotein-ε4 is associated with higher fecundity in a natural fertility population

In many populations, the apolipoprotein-ε4 (APOE-ε4) allele increases the risk for several chronic diseases of aging, including dementia and cardiovascular disease; despite these harmful effects at later ages, the APOE-ε4 allele remains prevalent. We assess the impact of APOE-ε4 on fertility and its proximate determinants (age at first reproduction, interbirth interval) among the Tsimane, a natural fertility population of forager-horticulturalists. Among 795 women aged 13 to 90 (20% APOE-ε4 carriers), those with at least one APOE-ε4 allele had 0.3 to 0.5 more children than (ε3/ε3) homozygotes, while those with two APOE-ε4 alleles gave birth to 1.4 to 2.1 more children. APOE-ε4 carriers achieve higher fertility by beginning reproduction 0.8 years earlier and having a 0.23-year shorter interbirth interval. Our findings add to a growing body of literature suggesting a need for studies of populations living in ancestrally relevant environments to assess how alleles that are deleterious in sedentary urban environments may have been maintained by selection throughout human evolutionary history.

Traditional and biomedical maternal and neonatal care practices in a rural Indigenous population of the Bolivian Amazon

In recent decades, Bolivia has expanded maternal and child health insurance coverage to improve access to prenatal and early life health care. Nationally, however, maternal and child health disparities persist along a rural-urban divide. Research is needed among rural populations to better understand local barriers to health care access and usage. Particularly among Indigenous populations, disparities may be compounded by differences in preferences for and access to traditional versus biomedical health care. We examined prenatal care and birth practices among Tsimane forager-farmers of El Beni, Bolivia. From 2012-2013, we interviewed 151 Tsimane mothers (0-35 months postpartum) from nine villages about birth and neonatal care practices, prenatal care, and pharmaceutical usage during labour and postpartum recovery. Results demonstrate local disparities in biomedical care usage by ease of access (e.g. proximity to market town, Spanish fluency), and maternal experience (e.g. parity and prior offspring death or miscarriage). While 59% of interviewed mothers had received at least one prenatal screening, services performed in screenings were limited. Nearly all women continue to birth at home with family assistance. Inconsistent access to health care services may be exacerbated by regional, generational, and educational disparities within the population.

Postpartum depression and mother-offspring conflict over maternal investment

BACKGROUND AND OBJECTIVES

As the mother-offspring relationship is central to human reproduction, postpartum depression symptoms are difficult to explain in evolutionary terms. We proposed that postpartum depression might arise as a result of evolutionary mother-offspring conflict over maternal investment, and investigated the association between postpartum depression symptoms, infant night waking, maternal sleep disturbance and breastfeeding frequency.

METHODOLOGY

We conducted a cross-sectional analysis using survey responses at 6 months postpartum from 1598 Finnish mothers. We hypothesized that infant night waking at 6 months postpartum would be associated with postpartum depression symptoms, and that this association would be mediated by maternal sleep disturbance and a higher breastfeeding frequency.

RESULTS

Infant night waking was moderately associated with postpartum depression symptoms, and this association was mediated by maternal sleep disturbance (R 2=0.09). Contrary to our prediction, we found that increased breastfeeding was associated with less postpartum depression symptoms.

CONCLUSIONS AND IMPLICATIONS

We conclude that postpartum depression symptoms might partly be the result of increased maternal fatigue stemming from high offspring demands on maternal investment, but that this is not due to the metabolic strain from increased breastfeeding. Studying postpartum depression from the mother-offspring conflict perspective can potentially improve our understanding of the involved behavioral processes of both mother and offspring, and allow interventions designed to benefit the well-being of both parties. Lay Summary: We proposed that postpartum depression is due to an evolutionary conflict between mother and infant, where the infant tires the mother to delay the arrival of a sibling. We found a link between infant night waking and postpartum depression, mediated by the mother's sleep, but not by breastfeeding frequency.

Evidence for height and immune function trade-offs among preadolescents in a high pathogen population

BACKGROUND

In an energy-limited environment, caloric investments in one characteristic should trade-off with investments in other characteristics. In high pathogen ecologies, biasing energy allocation towards immune function over growth would be predicted, given strong selective pressures against early-life mortality.

METHODOLOGY

In the present study, we use flow cytometry to examine trade-offs between adaptive immune function (T cell subsets, B cells), innate immune function (natural killer cells), adaptive to innate ratio and height-for-age z scores (HAZ) among young children (N = 344; aged 2 months-8 years) in the Bolivian Amazon, using maternal BMI and child weight-for-height z scores (WHZ) as proxies for energetic status.

RESULTS

Markers of adaptive immune function negatively associate with child HAZ, a pattern most significant in preadolescents (3+ years). In children under three, maternal BMI appears to buffer immune and HAZ associations, while child energetic status (WHZ) moderates relationships in an unexpected direction: HAZ and immune associations are greater in preadolescents with higher WHZ. Children with low WHZ maintain similar levels of adaptive immune function, but are shorter compared to high WHZ peers.

CONCLUSIONS

Reduced investment in growth in favor of immunity may be necessary for survival in high pathogen contexts, even under energetic constraints. Further, genetic and environmental factors are important considerations for understanding variation in height within this population. These findings prompt consideration of whether there may be a threshold of investment into adaptive immunity required for survival in high pathogen environments, and thus question the universal relevance of height as a marker of health.

LAY SUMMARY

Adaptive immune function is negatively associated with child height in this high pathogen environment. Further, low weight-for-height children are shorter but maintain similar immune levels. Findings question the relevance of height as a universal health marker, given that costs and benefits of height versus immunity may be calibrated to local ecology.

[A quantitative and qualitative study of exclusive breastfeeding intention by high-risk pregnant women]

The scope of this research was to assess the breastfeeding intention among high-risk pregnant women and related factors. It is a cross-sectional, qualitative and quantitative study, with 1,118 high-risk pregnant women who attended the prenatal care unit at a specialized center of the Unified Health System. The dependent variables were exclusive breastfeeding intention, intended duration and conditions that might interfere with breastfeeding. The Epi Info 7.4.1, Bioestat 5.3 and IRAMUTEQ 0.7.2.0 programs were used for data processing. The results showed that 8.76% of the pregnant women had conditions that could affect lactation. Among the women, 93.83% affirmed having exclusive breastfeeding intention, of which 69.86% intended to breastfeed until the child was six months old, revealing an association with sociodemographic variables (p<0.05). The intended breastfeeding duration was related to the age (p=0.0041), marital status (p=0.0053) and level of education (p=0.0116). The main reasons reported for not providing exclusive breastfeeding were the following: HIV, use of medications, work and lack of information. This research concluded that a small cohort of high-risk pregnant women presented conditions that could interfere with breastfeeding. Most of them intended to breastfeed exclusively for six months.

Microbiota assembly, structure, and dynamics among Tsimane horticulturalists of the Bolivian Amazon

Selective and neutral forces shape human microbiota assembly in early life. The Tsimane are an indigenous Bolivian population with infant care-associated behaviors predicted to increase mother-infant microbial dispersal. Here, we characterize microbial community assembly in 47 infant-mother pairs from six Tsimane villages, using 16S rRNA gene amplicon sequencing of longitudinal stool and tongue swab samples. We find that infant consumption of dairy products, vegetables, and chicha (a fermented drink inoculated with oral microbes) is associated with stool microbiota composition. In stool and tongue samples, microbes shared between mothers and infants are more abundant than non-shared microbes. Using a neutral model of community assembly, we find that neutral processes alone explain the prevalence of 79% of infant-colonizing microbes, but explain microbial prevalence less well in adults from river villages with more regular access to markets. Our results underscore the importance of neutral forces during microbiota assembly. Changing lifestyle factors may alter traditional modes of microbiota assembly by decreasing the role of neutral processes.

Selective and neutral forces shape human microbiota assembly in early life. Here, Sprockett et al. study microbial community assembly in 47 infant-mother pairs from the Tsimane, an indigenous Bolivian population, highlighting the importance of neutral forces during microbiota assembly.

Crucial Contributions : A Biocultural Study of Grandmothering During the Perinatal Period

Maternal grandmothers play a key role in allomaternal care, directly caring for and provisioning their grandchildren as well as helping their daughters with household chores and productive labor. Previous studies have investigated these contributions across a broad time period, from infancy through toddlerhood. Here, we extend and refine the grandmothering literature to investigate the perinatal period as a critical window for grandmaternal contributions. We propose that mother-daughter co-residence during this period affords targeted grandmaternal effort during a period of heightened vulnerability and appreciable impact. We conducted two focus groups and 37 semi-structured interviews with Himba women. Interviews focused on experiences from their first and, if applicable, their most recent birth and included information on social support, domains of teaching and learning, and infant feeding practices. Our qualitative findings reveal three domains in which grandmothers contribute: learning to mother, breastfeeding support, and postnatal health and well-being. We show that informational, emotional, and instrumental support provided to new mothers and their neonates during the perinatal period can aid in the establishment of the mother-infant bond, buffer maternal energy balance, and improve nutritional outcomes for infants. These findings demonstrate that the role of grandmother can be crucial, even when alloparenting is common and breastfeeding is frequent and highly visible. Situated within the broader anthropological and clinical literature, these findings substantiate the claim that humans have evolved in an adaptive sociocultural perinatal complex in which grandmothers provide significant contributions to the health and well-being of their reproductive-age daughters and grandchildren.

Old friends and friendly fire: Pregnancy, hookworm infection, and anemia among tropical horticulturalists

OBJECTIVES

Despite public health concerns about hookworm infection in pregnancy, little is known about immune profiles associated with hookworm (Necator americanus and Ancylostoma duodenale) infection during pregnancy. Fetal tolerance requirements may constrain maternal immune response to hookworm, thereby increasing susceptibility to new infections or increasing hemoglobin loss. To explore this possibility, we study systemic immune response and hemoglobin levels in a natural fertility population with endemic helminthic infection.

METHODS

We used Bayesian multilevel models to analyze mixed longitudinal data on hemoglobin, hookworm infection, reproductive state, eosinophils, and erythrocyte sedimentation rate (ESR) to examine the effects of pregnancy and hookworm infection on nonspecific inflammation, cellular parasite response, and hemoglobin among 612 Tsimane women aged 15-45 (1016 observations).

RESULTS

Pregnancy is associated with lower eosinophil counts and lower eosinophil response to hookworm, particularly during the second and third trimesters. Both hookworm and pregnancy are associated with higher ESR, with evidence for an interaction between the two causing further increases in the first trimester. Pregnancy is moderately associated with higher odds of hookworm infection (OR: 1.23, 95% CI: 0.83 to 1.83). Pregnancy and hookworm both decrease hemoglobin and may interact to accentuate this effect in the first-trimester of pregnancy (Interaction: β: -0.30 g/dL; CI: -0.870 to 0.24).

CONCLUSIONS

Our findings are consistent with a possible trade-off between hookworm immunity and successful pregnancy, and with the suggestion that hookworm and pregnancy may have synergistic effects, particularly in the first trimester.

Cultura dos povos originários da floresta amazônica na gestação e no puerpério: uma revisão de escopo sob o ponto de vista da segurança alimentar e nutricional

RESUMO A desnutrição na população indígena é um problema de saúde pública atual e uma das principais causas de morbimortalidade das crianças desses grupos no Brasil. Para subsidiar ações de promoção da educação alimentar e nutricional, abrangendo povos da floresta do estado do Amazonas, Brasil, cujo território faz fronteira com a Colômbia, além da visita de campo em 2018, fez-se necessário, concomitantemente, mapear na literatura como essa população vive e de que maneira o cuidado é prestado. A revisão de escopo buscou tópicos referentes ao modo de vida das mulheres e crianças na Amazônia, à dieta durante o período gestacional e do puerpério, a práticas de aleitamento, à introdução de alimentos sólidos ao bebê e aos cuidados dos serviços de saúde. Como resultado, foram recuperados 21 estudos multidisciplinares. Encontrou-se que a comida tradicional tem valor nutricional maior do que a industrializada, a culinária local é uma fonte de renda das mulheres indígenas no meio urbano e um elo entre etnias. Conclui-se que as pesquisas devem incorporar o paradigma da promoção da saúde e abranger temas como a aculturação indígena nos centros urbanos amazônicos, a chegada da internet nas aldeias e o papel do cuidado à distância, que necessitam ser investigados para melhor enfrentamento do problema.

Differences in Tsimane children's growth outcomes and associated determinants as estimated by WHO standards vs. within-population references

Anthropometric measures are commonly converted to age stratified z-scores to examine variation in growth outcomes in mixed-age and sex samples. For many study populations, z-scores will differ if calculated from World Health Organization (WHO) growth standards or within-population references. The specific growth reference used may influence statistical estimates of growth outcomes and their determinants, with implications for biological inference. We examined factors associated with growth outcomes in a sample of 152 Tsimane children aged 0-36 months. The Tsimane are a subsistence-scale population in the Bolivian Amazon with high rates of infectious disease and growth faltering. To examine the influence of growth reference on statistical inferences, we constructed multiple plausible models from available infant, maternal, and household attributes. We then ran identical models for height-for-age (HAZ), weight-for-age (WAZ), and weight-for-height (WHZ), with z-scores alternately calculated from WHO and robust Tsimane Lambda-Mu-Sigma growth curves. The distribution of WHO relative to Tsimane HAZ scores was negatively skewed, reflecting age-related increases in lower HAZ. Standardized coefficients and significance levels generally agreed across WHO and Tsimane models, although the strength and significance of specific terms varied in some models. Age was strongly, negatively associated with HAZ and WAZ in nearly all WHO, but not Tsimane models, resulting in consistently higher R2 estimates. Age and weaning effects were confounded in WHO models. Biased estimates of determinants associated with WHO HAZ may be more extreme in small samples and for variables that are strongly age-patterned. Additional methodological considerations may be warranted when applying WHO standards to within-population studies, particularly for populations with growth patterns known to systematically deviate from those of the WHO reference sample.

Birth mode, breastfeeding and childhood infectious morbidity in the Yucatec Maya

OBJECTIVES

Cesarean delivery is linked to breastfeeding complications and child morbidity. These outcomes may disproportionately affect Latin American indigenous populations that are experiencing rising cesarean delivery rates, but often inhabit environments that exacerbate postnatal morbidity risks. We therefore assess relationships between birth mode, infant feeding practices, and childhood infectious morbidity in a modernizing Yucatec Maya community, where prolonged breastfeeding is the norm. We predicted that under these conditions, cesarean delivery would increase risk of childhood infectious morbidity, but prolonged breastfeeding postcesarean would mitigate morbidity risk.

METHODS

Using a longitudinal child health dataset (n = 88 children aged 0-60 months, 24% cesarean-delivered, 2290 observations total), we compare gastrointestinal infectious (GI) and respiratory infectious (RI) morbidity rates by birth mode. We model associations between cesarean delivery and breastfeeding duration, formula feeding and child nutritional status, then model GI and RI as a function of birth mode, child age, and feeding practices.

RESULTS

Cesarean delivery was associated with longer breastfeeding durations and higher child weight-for-age, but not with formula feeding, GI, or RI. Adolescent motherhood and RI were risk factors for GI; formula feeding and GI were risk factors for RI. Regional housing materials protected against GI; breastfeeding protected against RI and mitigated the effect of formula feeding.

CONCLUSIONS

We find no direct link between birth mode and child infectious morbidity. Yucatec Maya mothers practice prolonged breastfeeding, especially postcesarean, and in conjunction with formula feeding. This practice protects against childhood RI, but not GI, perhaps because GI is more susceptible to maternal and household factors.

Variation among populations in the immune protein composition of mother's milk reflects subsistence pattern

LAY SUMMARY

Adaptive immune proteins in mothers' milk are more variable than innate immune proteins across populations and subsistence strategies. These results suggest that the immune defenses in milk are shaped by a mother's environment throughout her life.

BACKGROUND AND OBJECTIVES

Mother's milk contains immune proteins that play critical roles in protecting the infant from infection and priming the infant's developing immune system during early life. The composition of these molecules in milk, particularly the acquired immune proteins, is thought to reflect a mother's immunological exposures throughout her life. In this study, we examine the composition of innate and acquired immune proteins in milk across seven populations with diverse disease and cultural ecologies.

METHODOLOGY

Milk samples (n = 164) were collected in Argentina, Bolivia, Nepal, Namibia, Philippines, Poland and the USA. Populations were classified as having one of four subsistence patterns: urban-industrialism, rural-shop, horticulturalist-forager or agro-pastoralism. Milk innate (lactalbumin, lactoferrin and lysozyme) and acquired (Secretory IgA, IgG and IgM) protein concentrations were determined using triple-quadrupole mass spectrometry.

RESULTS

Both innate and acquired immune protein composition in milk varied among populations, though the acquired immune protein composition of milk differed more among populations. Populations living in closer geographic proximity or having similar subsistence strategies (e.g. agro-pastoralists from Nepal and Namibia) had more similar milk immune protein compositions. Agro-pastoralists had different milk innate immune protein composition from horticulturalist-foragers and urban-industrialists. Acquired immune protein composition differed among all subsistence strategies except horticulturist-foragers and rural-shop.

CONCLUSIONS AND IMPLICATIONS

Our results reveal fundamental variation in milk composition that has not been previously explored in human milk research. Further study is needed to understand what specific aspects of the local environment influence milk composition and the effects this variation may have on infant health outcomes.

Child nutritional status among births exceeding ideal family size in a high fertility population

Ideal family size (IFS) is measured in social surveys to indicate unmet need for contraception and impending shifts in fertility behaviour. Whether exceeding IFS affects parental behaviour in ways that result in lower investments in child nutrition, well-being, and educational attainment is not known. This study examines parental IFS and the association between exceeding stated ideals and child nutritional status in a high-fertility, high-mortality population in the Bolivian Amazon. Height-for-age z-scores, weight-for-age z-scores, weight-for-height z-scores, stunting, haemoglobin, and anaemia status in 638 children aged 0-5 years are predicted as a function of birth order in relation to parental IFS, adjusting for household characteristics and mother and child random effects. Children of birth orders above paternal IFS experience higher weight-for-age z-scores when living further away from the market town of San Borja, consistent with underlying motivations for higher IFS and lower human capital investment in children in more remote areas (β = .009, p = .027). Overall, we find no statistical evidence that birth orders in excess of parental ideals are associated with compromised child nutrition below age 2, a period of intensive breastfeeding in this population. Despite a vulnerability to nutritional deficiencies postweaning for children age 2-5, there was no association between birth order in excess of parental ideals and lower nutritional status. Further studies examining this association at various stages of the fertility transition will elucidate whether reported ideal or optimal family sizes are flexible as trade-offs between quality and quantity of children shift during the transition to lower fertility.

Parental investment in Tibetan populations does not reflect stated cultural norms

In this paper, we examined both stated norms of sex preference and actual sex-biases in parental investment in a Tibetan pastoralist society. We collected detailed demographic data on infant mortality, infant feeding, the length of interbirth intervals, and a decision when giving gifts, to examine sex-biased parental investment. Our results indicate a mismatch between self-reported son preference and measures of actual parental investment that favor daughters. We interpret this female-biased parental investment as a possible response to daughters generating more economic resources. However, the stated sex preferences of both sexes reflect cultural norms that appear to have remained unchanged over a long period, which may reflect the importance of male roles in the past. Our behavioral measures of parental investment are those most likely to be in the control of women (such as breastfeeding and interbirth interval), so this mismatch between stated and actual investment may be especially true of women.

The Tsimane Health and Life History Project: Integrating anthropology and biomedicine

The Tsimane Health and Life History Project, an integrated bio-behavioral study of the human life course, is designed to test competing hypotheses of human life-history evolution. One aim is to understand the bidirectional connections between life history and social behavior in a high-fertility, kin-based context lacking amenities of modern urban life (e.g. sanitation, banks, electricity). Another aim is to understand how a high pathogen burden influences health and well-being during development and adulthood. A third aim addresses how modernization shapes human life histories and sociality. Here we outline the project's goals, history, and main findings since its inception in 2002. We reflect on the implications of current findings and highlight the need for more coordinated ethnographic and biomedical study of contemporary nonindustrial populations to address broad questions that can situate evolutionary anthropology in a key position within the social and life sciences.

Growth references for Tsimane forager-horticulturalists of the Bolivian Amazon

OBJECTIVES

Growth standards and references currently used to assess population and individual health are derived primarily from urban populations, including few individuals from indigenous or subsistence groups. Given environmental and genetic differences, growth may vary in these populations. Thus, there is a need to assess whether international standards are appropriate for all populations, and to produce population specific references if growth differs. Here we present and assess growth references for the Tsimane, an indigenous population of Bolivian forager-horticulturalists.

METHODS

Mixed cross-sectional/longitudinal anthropometrics (9,614 individuals; 30,118 observations; ages 0-29 years) were used to generate centile curves and Lambda-Mu-Sigma (LMS) tables for height-for-age, weight-for-age, body mass index (BMI)-for-age, and weight-for-height (WFH) using Generalized Additive Models for Location Shape and Scale (GAMLSS). Velocity curves were generated using SuperImposition by Translation and Rotation (SITAR). Tsimane ≤5 years were compared to World Health Organization (WHO) standards while those >5 years were compared to WHO school age references. All ages were compared to published references for Shuar forager-horticulturalists of the Ecuadorian Amazon.

RESULTS

Tsimane growth differs from WHO values in height and weight, but is similar for BMI and WFH. Tsimane growth is characterized by slow height velocity in childhood and early adolescent peak height velocity at 11.3 and 13.2 years for girls and boys. Tsimane growth patterns are similar to Shuar, suggesting shared features of growth among indigenous South Americans.

CONCLUSIONS

International references for BMI-for-age and WFH are likely appropriate for Tsimane, but differences in height-for-age and weight-for-age suggest Tsimane specific references may be useful for these measures.