Evidence for an association between maternal depression and infant body size is mixed. We test the association between maternal depressive symptoms (MDS) and infant weight-for-age z-scores (iWAZ). Data come from 371 African American mother-infant pairs participating in the Mothers & Others Study, a home-based intervention to prevent early development of obesity. Data were collected at 28-weeks gestation and 3, 6, 9, 12, and 15 months postpartum. At each visit, infant weight was measured and MDS, breastfeeding history, infant feeding styles, and infant temperament were collected using validated instruments. Longitudinal mixed effects models tested the association between MDS and iWAZ. Path analyses tested for mediation by breastfeeding duration, responsive feeding, and infant fussiness. MDS were included in final models as a 4-level categorical variable to test whether the timing and/or duration of MDS were differently associated with iWAZ. Prevalence of MDS ranged from 30.4% prenatally to 13.9% at 15 months. MDS were inversely associated with iWAZ in adjusted models. No evidence for mediation through breastfeeding or responsive feeding was found. MDS had a significant indirect effect through perception of infant fussiness (β=0.02, CI: 0.01, 0.04). Infants of mothers with both pre- and postnatal symptoms had significantly smaller iWAZ from 0-15 months (β=-0.41, p=0.03) than infants of mothers without depressive symptoms. Our analysis suggests that MDS are associated with lower iWAZ. Maternal perception of infant temperament may be an underlying pathway, but more research is needed to understand the effects of maternal depression on body size.

Microbial exposures during infancy shape the development of the microbiome, the collection of microbes living in and on the body, which in turn directs immune system training. Newborns acquire a substantial quantity of microbes during birth and throughout infancy via exposure to microbes in the physical and social environment. Alterations to early life microbial environments may give rise to mismatches, where environmental, cultural, and behavioral changes that outpace the body’s adaptive responses can lead to adverse health outcomes, particularly those related to microbiome development and immune system regulation. This study explored the development of the skin microbiome among infants born in Chicago, USA. We collected skin swab microbiome samples from 22 mother-infant dyads during the first 48 hours of life and again at six weeks postpartum. Mothers provided information about birth and household environments, as well hygiene behaviors that may impact infants’ microbial exposures. Analysis of 16S rRNA bacterial gene sequencing data revealed correlations between infant skin bacterial abundances shortly after birth and factors such as antibiotic exposure and receiving a bath in the hospital. The composition of the infant microbiome at six weeks of age was associated with interactions with caregivers and infant feeding practices. We also found shifts in maternal skin microbiomes that may reflect increased hygiene practices in the hospital. Our data suggest that factors related to the birth and household environment can impact the development of infant skin microbiomes and point to practices that may produce mismatches for the infant microbiome and immune system.

Despite government efforts to improve breastfeeding and complementary feeding, northern Brazil posts the poorest adherence to infant feeding guidelines and highest rate of infant growth faltering. To better understand complementary feeding practices in the region, we collected data on breastfeeding and dietary intake (24-hr dietary recall) from a longitudinal cohort of n=168 infants at 1-month, 3-months, 9-months, and 15-months living in high- and low-socio-economic-status households (HSES, LSES) in Belém. We complemented these data with interviews with n=30 mothers regarding infant feeding decisions. We used the FAO definitions for exclusive/mixed breastfeeding and followed their protocol for calculating minimum dietary diversity (MDD). Breastfeeding patterns did not differ between HSES and LSES infants at 1, 3 and 9-months. However, by 15-months, LSES infants were more likely to be breastfed (X2=4.04; p=0.04). At 3-months, both HSES and LSES infants received other foods, mainly cereals and cow’s milk, and this was more frequent among LSES infants. At 9-months we documented cereals/roots/tubers, dairy, flesh foods, and Vit-A rich fruits/vegetables in infants’ diets and found no differences in MDD between the HSES and LSES groups (Mann-Whitney=2008; p=0.55). By 15-months infants were consuming foods from the cereals/roots/tubers, dairy, flesh foods, Vit-A rich fruits/vegetables, and legumes/nuts/seeds categories, and MDD was higher among HSES infants (Mann-Whitney=2180; p=0.04). We also found that LSES infants were more exposed to sugar and other ultra-processed foods. A review of the food items consumed, and thematic analysis of the interview transcripts indicate that an understanding of the biocultural context is needed to improve infant outcomes.

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 behavior and may lead to suboptimal infant and young child nutrition. 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. We used 24 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. We found that higher wet-bulb temperatures predicted reduced daily breastfeeding time allocation, particularly among fishers, and drove shifts toward increased nighttime and decreased mid/late morning feeding. Maternal occupation and the interaction of child age with heat strongly influenced diurnal breastfeeding patterns. These results highlight an important role of maternal work on infants’ vulnerability to environmental stress. Dyads’ ability to behaviorally 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.

Urinary cell-free mitochondrial DNA (cf-mtDNA) – the concentration of extracellular mtDNA excreted in urine – is an emerging biomarker of stress and metabolic adaptation. Among humans, cf-mtDNA is elevated by both physical and psychosocial stressors and is linked to increased metabolism, biological aging, and greater illness symptom severity. This research has been restricted to adults in industrialized settings. Here, we provide the first early life and low- and middle-income country (LMIC) data for cf-mtDNA. Untimed urine samples, anthropometric measures, and other data were collected from 81 Indigenous Shuar children (aged 4-12 years) in Amazonian Ecuador. Urine samples were processed and cf-mtDNA quantified using qPCR, corrected for creatinine. Mixed effects regression models indicate significant independent effects of sex, BMI-for-age (BAZ), and rural/peri-urban group on cf-mtDNA. Specifically, cf-mtDNA concentration was greater among females (p < 0.001), was negatively related to BAZ (p = 0.008), and was elevated 51% among children living in a rural setting (p = 0.039). Analysis of pathogen exposure variables among the Shuar identified a possible protective effect of clean drinking water, such that households with piped (vs. fetched) water had 68% lower cf-mtDNA (p = 0.022). As a predictor, Shuar children with higher cf-mtDNA exhibited lower height-for-age z-score measures of linear growth (p = 0.041). These preliminary findings demonstrate that cf-mtDNA is broadly linked to children’s physical stress, energetics, and growth in an LMIC context. As such, cf-mtDNA provides human biologists with a novel and potentially powerful tool for investigating pathways of embodiment, developmental plasticity, and life history trade-offs.

The Qom/Toba of northern Argentina, like many Indigenous Peoples undergoing drastic lifestyle changes, are facing increasing challenges with substance use, particularly glue inhalation among children. To date, no biosocial research has focused on childhood substance use in this community. This study, initiated at the community's request, aimed to explore social and cultural factors contributing to substance use among Qom children. The results of this study will inform culturally sensitive interventions to prevent substance use among Indigenous youth.

We conducted semi-structured interviews with 29 adults and 39 children (ages 6-12), recruited through snowball sampling, and collected additional qualitative data through participant observation. The data were coded and analyzed thematically.

Protective factors at the individual level included having friends who abstain, attending school, involvement in community organizations, spiritual beliefs, and supportive adults. Systemic risk factors included limited education about substance use, lack of resources, unemployment, social marginalization, and barriers within healthcare and government systems related to representation, language, and culture. Further research and community-based interventions that center Qom values and leadership are essential to addressing childhood substance use and promoting children's health in this population.

The Tengger Tribe is a traditional population in Indonesia that has distinctive local wisdom and formed a Java Hinduism belief system. The tribe lives around the Bromo Tengger Semeru National Park Area (1400-1900 masl) as an agricultural society. Life history explains that selective pressures, such as biocultural and ecological conditions, could influence energy allocation between productive (growth and reproduction), self-maintenance, and activity, resulting in various biological traits, such as somatotype. The research aims to determine the somatotype and physical activity levels (PAL) of the Tengger Tribe aged 12-20 years. A cross-sectional study was conducted on 351 subjects (185 girls and 166 boys). The somatotype was assessed using the Heath-Carter method. Physical activity was collected through 24-hour recall and calculated for PAL. The results showed that girls’ somatotype categories shifted from balanced endomorph to mesomorphic endomorph, while boys changed from balanced endomorph to central, balanced ectomorph, and back to central. The changes in somatotype components are likely related to PAL categories (girls: sedentary to heavy; boys: sedentary to moderate). Tengger’s somatotypes, characterized by endomorphic (fat) and mesomorphic (skeletal muscle) in both sexes, suggest a remarkable adaptive strategy for energy efficiency to temperature regulation, high physical activity in agricultural practices, and future reproductive demands. Our results align with the 'Mobility and Agility' hypothesis, underlining a muscular physique as an advantageous evolutionary strategy for navigation efficiency in challenging geographical conditions. These findings have significant implications for understanding human evolution and the influence of biocultural and ecological factors on biological traits.

Little is known about "folk conceptions" of sleep function and sleep problems in non-WEIRD settings. Here, we analyze adolescent perceptions of sleep among 145 participants (x̄=13.7 ± 1.21) belonging to three distinct ecological backgrounds: 1) Totonac agriculturalists, 2) Maya agriculturalists, and 3) urbanites from Mexico City. We predict that the rural adolescents who are not influenced by the same cultural factors as WEIRD participants (e.g., gendered physical activity, technological gadgets with screens, and the materiality of sleep) will have fewer sleep complaints. From February to November 2019, we collected 1405 sleep observations employing actigraphy, interviews, and ethnographic observations. We used a thematic analysis to investigate the participants' sleep quality and culturally normative ideas about sleep. Adolescents from Mexico City expressed the shortest sleep durations and the highest sleep efficiency (SE, defined as the ratio of total sleep time to time in bed) (Mdn=87.6, IQR=7.7); Maya teenagers had a similar duration but significantly lower SE (Mdn=76.5, IQR=13.8). However, regarding self-rated daytime drowsiness, individuals from Mexico City scored the highest and those from Puebla the lowest. Urban teenagers quantified their sleeping times to assess whether they had a good night’s sleep, whereas rural teenagers relied on their subjective bodily experience of restedness. Results suggest that sociocultural cues can substantially impact objective and subjective sleep outcomes.

While reproduction and family formation are deeply intertwined with biological processes, a variety of social factors affect at least three aspects of this process: desire, intent, and success. Disparities in these aspects are found between lesbian, gay, bisexual, transgender, and queer (LGBTQ+) and non-LGBTQ+ individuals, with LGBTQ+ individuals being less likely to intend to and succeed in family formation. These disparities are affected by personal beliefs, structural barriers, and individual experiences, as LGBTQ+ individuals are less able to access necessary resources for family formation and may therefore be discouraged from doing so. Furthermore, early-life experiences, including negative parental relationships, can affect personal beliefs and biological abilities of childbearing through pathways of stress. To explore the association between early parental relationships and adult experiences of family formation (having children, or if not, reasons for not doing so) in LGBTQ+ individuals, data from the National Longitudinal Study of Adolescent to Adult Health (Add Health) in Wave I (1994-1995) and Wave IV (2008-2009, adulthood) are used. Relationships between adolescent parental relationships, adult perceived stress, and family formation intent and success were assessed in 588 LGBTQ+ participants in comparison to their heterosexual peers. Our results suggest that LGBTQ+ individuals experience more negative parental relationships in adolescence, have lower intent and success in family formation, and have higher levels of stress compared to non-LGBTQ+ individuals. These results will shed light on the multitude of processes related to family formation and open up avenues of inquiry for potential intergenerational effects of stress in this population.

Persistent organic pollutants (POPs), in particular polychlorinated biphenyls (PCBS), are known to be lipophilic and are associated with many adverse health effects in humans, such as alterations to sexual maturation and growth and development. We utilized longitudinal measurements of POP levels, height, weight, and sexual maturation from two studies, the Mohawk Adolescent Well-Being Study (1995-2000) and the Young Adult Well-Being study (2000-2005) which included participants from adolescence to adulthood, to quantify individual-level change in a community with documented exposure to POPs. We hypothesized there would be a significant association between changes in POPs levels, and changes in growth and development. The POPs included in this analysis include dichlorodiphenyldichloroethylene (p,p’-DDE), hexachlorobenzene (HCB), and PCBs (persistent, non-persistent, and airborne). The average difference in age between the first and second set of measurements was 4.52 years (+ 1.21). An increase in summary PCB50 levels was associated with less height attainment (p=0.016) while an increase in p,p’-DDE levels was correlated with less weight attainment (p<0.001) between samples. Congener specific analyses found age was significantly and positively correlated with increased levels of PCB123. Higher levels of PCB74 and PCB187 were correlated with less height attainment (p=0.012; p<0.001 respectively). Increased levels of PCB74 and PCB187 were associated with a greater likelihood of reaching Tanner Stage II (p=0.003). In contrast, PCB110 was correlated with a decreased likelihood of reaching Tanner Stage II (p=0.027). Additional multivariate predictive modeling will further analyze and characterize relationships between changes in POP levels with height, weight, and sexual maturation.

Background: Adolescence is a critical transition in which girls face energetic trade-offs between growth and reproductive development. These trade-offs can affect the onset and pace of this transition in girls. The hypothalamic-pituitary-adrenal axis (HPAA) is a proposed modulator of metabolic energetic trade-offs, yet, few studies have examined its role during girls’ reproductive maturation. Hypothesis: The HPAA modulates metabolic energy allocation between growth and reproductive maturation. We predict that timing of menarche should be linked to energy storage levels and progress of somatic growth. Methods: We evaluated biomarkers of HPAA activity (cortisol), energy uptake (c-peptide), energy storage (adiponectin) and ovarian function (estrogen and progesterone metabolites quantified in first morning urine), and measures of height growth (proportion of final height) collected from 29 pre- and post-menarche Mayan adolescent girls from Guatemala. Results: Adiponectin’s relationship with menarche timing was modulated by cortisol; for each unit of cortisol by adiponectin interaction, girls were 8.56-months further from menarche. Additionally, for each 1% increase in proportion of their final height, girls were 1.34-months closer to menarche. Discussion: Consistent with our hypothesis, HPAA activity was associated with energy storage levels and time until menarche, which was linked to the pace of somatic growth. Future studies should include the frequent collection of anthropometric data and biomarkers throughout the transition from childhood to adolescence to explore within-individual changes in HPAA activity, energy levels and somatic development and the pace of reproductive and draw among-individual comparisons to further clarify the HPAA’s role in modulating energy allocation between growth and reproduction.

Many studies aim to understand the environmental drivers of life history strategy but rely on recall data for the timing of pubertal development. Epigenetic clocks, although designed to measure the pace of aging, are hypothesized to reflect the pace of development when measured in younger individuals and could provide a physiological measure of life history pacing. Here, we use data from a birth cohort study (the Cebu Longitudinal Health and Nutrition Survey) to test whether epigenetic age acceleration (EAA) measured in young adults (N > 1500) is associated with (a) biological life history traits, including age at maturation, and (b) behavioral characteristics of life history, such as age at first sex. We measure EAA with a panel of 9 epigenetic clocks (6 trained on adult populations, 3 on pediatric populations) and use a combination of survival analyses and logistic regression. The pediatric clocks were not associated with any outcome, suggesting that they do not serve as biomarkers of pubertal timing when measured in young adults. None of the adult clocks were associated with age at menarche in females or pubertal development in males. However, in adult clocks EAA consistently predicted earlier ages at first conception in females and earlier ages at first sex in both females and males. When analyses were repeated and limited to females nulliparous at baseline, these relationships were no longer present. These findings suggest that EAA indexes behavioral aspects of life history strategy, and that this partly reflects the age accelerating effects of reproduction in females.