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Objectives: In non‐industrialized and low‐income populations, adipose stores can serve as a valuable buffer against harsh conditions such as seasonal food scarcity. However, these reserves may incur costs due to adipocytes' production of pro‐inflammatory cytokines; inflammation is associated with increased risk for cardiometabolic diseases later in life. Life history theory posits that, especially in populations with high juvenile mortality, higher adiposity may nonetheless be advantageous if its benefits in early life outweigh its later costs. Relatively little is known about adolescents' C‐reactive protein concentration (CRP; an inflammation biomarker) in such environments. We investigated CRP and its associations with several hypothesized predictors in adolescents in an economically diverse peri‐urban Andean community. Methods: We measured CRP in dried blood spots and collected data on anthropometrics, illnesses, socioeconomic status (SES), and menarcheal status in 59 female and 40 male adolescents ("Alteños", 11.0–14.9 years old) with normal vital signs in El Alto, Bolivia (~4150 m amsl). We used Cole's LMS method to standardize all anthropometrics for sex and age, and principal components analysis to construct a "fat‐factor" variable loading on these standardized z‐scores. We used multiple linear regression to assess the influence of fat‐factor and other likely predictors on CRP rank. Results: Compared to a national Bolivian growth reference, Alteños were, on average, shorter and leaner; only 6% were classified as overweight and none were obese. Pre‐menarche females were on average leaner than post‐menarche females. The best‐fitting model explained 24% of the variance in CRP rank. Significant predictors were fat‐factor, SES, current illness for males and pre‐menarche females, and z‐height for females. Conclusions: Our results are consistent with a tradeoff between investments in growth versus immune functioning, as might be expected in an environment with limited resources and high pathogen exposure (e.g., soil‐transmitted helminths, poor sanitation). Thinner Alteños appear to maintain a minimum CRP concentration independent of fat‐factor, while fatter (or less‐thin) Alteños' CRP rises with fat‐factor. Female Alteños appear to be trading off investment in immune response for investment in growth and maturation. Alteños' high rate of stunting and absence of obesity suggests chronic, presumably multifactorial, stress. Adipose stores likely buffer against some of these stressors and, in an environment such as this—in which many lack sufficient nutritious foods, potable water, adequate sewage, and health care—may confer a net lifetime benefit. [ABSTRACT FROM AUTHOR]

Seasonal variation in photoperiod may affect psychosocial and physical well‐being in healthy persons. We tested this hypothesis in healthy pre‐menopausal women, without a history of mood disorders, living year‐round in Reykjavik, Iceland (64.1°N). Participants reported daily self‐assessments of well‐being throughout a complete ovulatory menstrual cycle in summer and/or winter (70% participated in both seasons). Scores for mood, cognitive acuity, social support, physical health and a composite of these four indicators were each significantly higher in summer than in winter (linear mixed effects models: p <.001 for each model); tiredness did not differ by season. The effect of season was not significantly changed by inclusion of body mass index and/or age as covariates. Some prior studies have been hampered by sparse time sampling, inattention to covariates and/or relying on recalled data. This is to our knowledge the first investigation to test the study hypothesis with daily real‐time data spanning complete ovulatory menstrual cycles in each of two seasons. This dense sampling has revealed modest seasonal variation in well‐being in healthy women. Daylength (sunlight exposure) is likely a major, but not necessarily sole, factor in these seasonal differences in well‐being; temperature is likely less important given Iceland's relatively moderate (for its high latitude) seasonal temperature swings. [ABSTRACT FROM AUTHOR]

The contraceptive needs of women for whom the benefits of menstrual bleeding may outweigh its disadvantages have largely been overlooked, especially outside high-income countries. Some providers and researchers have assumed that users of nonhormonal birth control (non-HBC) are misinformed about the positive and negative effects of HBC and/or the need for menstrual bleeding. This study takes the position that many of those rejecting HBC in favor of methods that do not alter bleeding are, in fact, making informed decisions. Using questionnaire data from 4,255 contraceptive users in three countries, we compared current HBC users explicitly open to hormone use ("H-receptive") and non-HBC users explicitly rejecting hormones ("H-averse"). To the extent that menstrual bleeding attitudes affect contraceptive choice, these two groups should have the greatest contrasts in those attitudes. This novel study design mitigates ambiguities arising from posing hypothetical scenarios to those ambivalent about using hormones or who are not currently using contraception. In all three countries, of those agreeing with the prompt, "I don't want to change my natural menstrual cycle," the fractions of H-averse and H-receptive users are disproportionally high and low, respectively (p ≤.0026). Responses to other prompts varied across populations, revealing complex juxtapositions of multiple criteria, including bleeding preferences, that likely influence contraceptive choices. These patterns, reflecting personal and culturally salient values, highlight the necessity of not assuming that menstrual bleeding is undesirable or relying on a single criterion to ascertain clients' contraceptive needs and preferences. Rather, acknowledging a client's personal hierarchy of preferences regarding contraceptive attributes best serves their goals. [ABSTRACT FROM AUTHOR]

Frank B. Livingstone: Introduction Frank B. Livingstone, Professor Emeritus of Biological Anthropology at the University of Michigan, Ann Arbor, was born in Winchester, MA, on December 8, 1928, an origin [...]

Objective: The study sought to build predictive models of next menstrual cycle start date based on mobile health self-tracked cycle data. Because app users may skip tracking, disentangling physiological patterns of menstruation from tracking behaviors is necessary for the development of predictive models.Materials and Methods: We use data from a popular menstrual tracker (186 000 menstruators with over 2 million tracked cycles) to learn a predictive model, which (1) accounts explicitly for self-tracking adherence; (2) updates predictions as a given cycle evolves, allowing for interpretable insight into how these predictions change over time; and (3) enables modeling of an individual's cycle length history while incorporating population-level information.Results: Compared with 5 baselines (mean, median, convolutional neural network, recurrent neural network, and long short-term memory network), the model yields better predictions and consistently outperforms them as the cycle evolves. The model also provides predictions of skipped tracking probabilities.Discussion: Mobile health apps such as menstrual trackers provide a rich source of self-tracked observations, but these data have questionable reliability, as they hinge on user adherence to the app. By taking a machine learning approach to modeling self-tracked cycle lengths, we can separate true cycle behavior from user adherence, allowing for more informed predictions and insights into the underlying observed data structure.Conclusions: Disentangling physiological patterns of menstruation from adherence allows for accurate and informative predictions of menstrual cycle start date and is necessary for mobile tracking apps. The proposed predictive model can support app users in being more aware of their self-tracking behavior and in better understanding their cycle dynamics. [ABSTRACT FROM AUTHOR]

Breastfeeding is known to have significant benefits for health of infants and is a factor in fecundity regulation for mothers. Mechanisms are not always well understood; variation exists across individuals and across populations. A fruitful area for further research lies in exploration of human lactation within an ecological framework, looking at different behaviors, among them different degrees of suckling activity. Cultural factors enter in, and implications are more than theoretical when it is considered that many places in the world lack safe water supplies and fuel and that some are in deserts.

Although a controversial issue in the not distant past, it is now well established that breastfeeding is the primary factor mediating post-partum subfecundity. This complex interaction between behavior and physiology is a central research focus in several fields sharing a common concern with the mechanisms that regulate human reproduction. Despite the demonstrated linkage between lactation and return of the first post-partum menses, many questions regarding the relationship between variation in breastfeeding behavior and variation in ovarian function remain unanswered. In particular, women of seemingly comparable breastfeeding magnitude display substantial heterogeneity in the duration of post-partum subfecundity. In addition, the hormonal mechanisms by which lactation regulates ovarian function remain unclear, and the debates regarding the contribution of factors other than breastfeeding to post-partum subfecundity continue unresolved. Part of the difficulty in addressing these questions derives from the use of disparate methodological approaches and an absence of specificity in analytical units. In particular, maternal recall of breastfeeding behavior is subject to substantial bias yet is the data source for most analyses. In addition, although a growing body of evidence suggests that variation in breastfeeding structure may contribute to variation in ovarian function, most studies fail to distinguish or evaluate the different components of suckling behavior. Elucidating the bases of this variation amongst women and populations requires disentangling the roles of the environment, culture, and behavior in structuring suckling activity. Anthropologists in particular have an opportunity to achieve significant insights into the ecology of human breastfeeding and reproduction. KEY WORDS Suckling patterns, Lactation, Post-partum amenorrhea, Fecundity, Fertility, Methods

Although there is evidence for reduced fertility in Andean and Himalayan populations at higher altitudes, factors other than hypoxia may be primarily responsible. A valuable approach in the investigation of these fertility determinants is the use of salivary steroid assays. However, coca-leaf chewing - a ubiquitous practice among high altitude Andean populations - has negative consequences for the accurate measurement of ovarian steroids. This report evaluates the effects of coca-leaf chewing on assays of salivary progesterone. Study participants include naive and habitual users of coca leaf from La Paz and El Alto, Bolivia. Approximately 300 saliva samples were collected immediately before, during, and after coca-leaf chewing. The series includes samples with and without the alkaloid enhancer typically used by coca-leaf chewers. Coca chewing produces false salivary progesterone values that mimic luteal phase values. On the basis of this study, an appropriate protocol is developed for the collection of salivary samples in coca-leaf chewing populations. These results verify the feasibility of salivary assays, even for very difficult field conditions, and highlight the necessity of establishing suitable collection procedures before full field implementation of saliva sampling.