C-reactive protein (CRP) in high altitude Bolivian peri-urban adolescents varies by adiposity, current illness, height, socioeconomic status, sex, and menarcheal status: The potential benefits and costs of adipose reserves in arduous environments.

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.

Socioeconomic impacts on Andean adolescents' growth: Variation between households, between communities and over time.

Background/objectives: We evaluated potential socioeconomic contributors to variation in Andean adolescents' growth between households within a peri-urban community undergoing rapid demographic and economic change, between different community types (rural, peri-urban, urban) and over time. Because growth monitoring is widely used for assessing community needs and progress, we compared the prevalences of stunting, underweight, and overweight estimated by three different growth references.

Methods: Anthropometrics of 101 El Alto, Bolivia, adolescents (Alteños), 11.

Recognizing normal reproductive biology: A comparative analysis of variability in menstrual cycle biomarkers in German and Bolivian women.

The idealized "normal" menstrual cycle typically comprises a coordinated ebb and flow of hormones over a 28-day span with ovulation invariably shown at the midpoint. It's a pretty picture-but rare. Systematic studies have debunked the myth that cycles occur regularly about every 28 days.

Impacts of nocturnal breastfeeding, photoperiod, and access to electricity on maternal sleep behaviors in a non-industrial rural Bolivian population.

Objectives: We tested 4 main predictions, derived from life history theory and self-evident human diurnality, regarding maternal sleep behaviors in a non-industrialized population in which mother-nursling co-sleeping is universal and prolonged: (1) Night breastfeeding incurs a sleep cost to co-sleeping mothers; (2) Night breastfeeding increases with infant age, causing mothers to sleep less; (3) Sleep duration co-varies with darkness duration; (4) Access to electricity reduces sleep duration.

Design: Mothers self-recorded and reported nursing and sleep behaviors for a 48-hour period once per month (median = 5 months).

Setting: Rural Bolivian altiplano homesteads, primarily reliant on agropastoralism, scattered throughout the countryside surrounding a main town (altitude 3800 m; 17°14'S, 65°55'W; darkness duration 10-12 hours over the year).

Factors Influencing the Use of Biomedical Health Care by Rural Bolivian Anemic Women: Structural Barriers, Reproductive Status, Gender Roles, and Concepts of Anemia.

Methods: Non-pregnant women from a rural town and its surrounding region were tested for anemia. During phase 1 (n = 181), anemic women received a written recommendation for low-cost purchase of iron pills at the nearest health center. They were subsequently interviewed on their actions and experiences.

Changes in blood gas transport of altitude native soccer players near sea-level and sea-level native soccer players at altitude (ISA3600).

Objectives: The optimal strategy for soccer teams playing at altitude is not known, that is, 'fly-in, fly-out' versus short-term acclimatisation. Here, we document changes in blood gas and vascular volumes of sea-level (Australian, n=20) and altitude (Bolivian, n=19) native soccer players at 3600 m.

Methods: Haemoglobin-oxygen saturation (Hb-sO₂), arterial oxygen content (CaO₂), haemoglobin mass (Hbmass), blood volume (BV) and blood gas concentrations were measured before descent (Bolivians only), together with aerobic fitness (via Yo-YoIR1), near sea-level, after ascent and during 13 days at 3600 m.

Methods of the international study on soccer at altitude 3600 m (ISA3600).

Background: We describe here the 3-year process underpinning a multinational collaboration to investigate soccer played at high altitude--La Paz, Bolivia (3600 m). There were two main aims: first, to quantify the extent to which running performance would be altered at 3600 m compared with near sea level; and second, to characterise the time course of acclimatisation of running performance and underlying physiology to training and playing at 3600 m. In addition, this project was able to measure the physiological changes and the effect on running performance of altitude-adapted soccer players from 3600 m playing at low altitude.

Exaggerated pulmonary hypertension during mild exercise in chronic mountain sickness.

Background: Chronic mountain sickness (CMS) is an important public health problem and is characterized by exaggerated hypoxemia, erythrocytosis, and pulmonary hypertension. While pulmonary hypertension is a leading cause of morbidity and mortality in patients with CMS, it is relatively mild and its underlying mechanisms are not known. We speculated that during mild exercise associated with daily activities, pulmonary hypertension in CMS is much more pronounced.

Seasonal modulation of reproductive effort during early pregnancy in humans.

Life history theory predicts that early pregnancy presents a relatively low cost, uncontested opportunity for a woman to terminate investment in a current reproductive opportunity if a conceptus is of poor quality and/or maternal status or environmental conditions are not propitious for a successful birth. We tested this hypothesis in rural Bolivian women experiencing substantial seasonal variation in workload and food resources. Significant risk factors for early pregnancy loss (EPL) included agropastoralism versus other economic strategies, conception during the most arduous seasons versus other seasons, and increasing maternal age.

Seasonal and circadian variation in salivary testosterone in rural Bolivian men.

Testosterone (T) plays a key role in the increase and maintenance of muscle mass and bone density in adult men. Life history theory predicts that environmental stress may prompt a reallocation of such investments to those functions critical to survival. We tested this hypothesis in two studies of rural Bolivian adult men by comparing free T levels and circadian rhythms during late winter, which is especially severe, to those in less arduous seasons.

Pulmonary-artery pressure and exhaled nitric oxide in Bolivian and Caucasian high altitude dwellers.

There is evidence that high altitude populations may be better protected from hypoxic pulmonary hypertension than low altitude natives, but the underlying mechanism is incompletely understood. In Tibetans, increased pulmonary respiratory NO synthesis attenuates hypoxic pulmonary hypertension. It has been speculated that this mechanism may represent a generalized high altitude adaptation pattern, but direct evidence for this speculation is lacking.

A prospective study of early pregnancy loss in humans.

Objective: To test two hypotheses: In spontaneous conceptions, early pregnancy loss (EPL) is associated with [1] inadequate luteal (ovarian) P, and/or [2] elevated follicular (adrenal) P.

Design: A population-based prospective study.

Setting: Thirty rural Bolivian communities.

Chronic mountain sickness, optimal hemoglobin, and heart disease.

For the male inhabitants of La Paz, Bolivia (3200-4100 m), and other high altitude regions in America and Asia, chronic mountain sickness (CMS) is a major health problem. Since CMS was first described by Carlos Monge in the Peruvian Andes in 1925, numerous research papers have been devoted to this topic, but many unanswered questions still exist with respect to the beginning of the disease and its cause(s). The experience with CMS has shown that an excessively high hemoglobin concentration is not favorable for high altitude acclimatization, and the hypothesis of theoretically "optimal" hematocrit and "optimal" hemoglobin has been made.

Epidemiological transitions, reproductive health, and the Flexible Response Model.

In concert with improving standards of living since the mid-19th century, chronic and non-infectious diseases replaced infectious diseases as the major causes of mortality in more developed countries. Thus, economic development has been seen as one strategy to improve women's reproductive health. However, rates of two of the major contributors to women's illness, maternal mortality and breast cancer, do not correspond well with the level of economic development.

Absence of work efficiency differences during cycle ergometry exercise in Bolivian Aymara.

This study tested the hypothesis that Andean natives are adapted to high altitude (HA) via high work efficiency during exercise in hypoxia. A total of 186 young males and females were tested in Bolivia, comprising eight different subject groups. Groups were identified based on gender, ancestry (Aymara vs.

Interpopulational differences in progesterone levels during conception and implantation in humans.

Clinical studies of women from the United States demonstrate a sensitivity of the ovarian system to energetic stress. Even moderate exercise or caloric restriction can lead to lower progesterone levels and failure to ovulate. Yet women in many nonindustrial populations experience as many as a dozen pregnancies in a lifetime despite poor nutritional resources, heavy workloads, and typical progesterone levels only about two-thirds of those of U.

Regression-based prediction of net energy expenditure in children performing activities at high altitude.

We developed a simple, non-invasive, and affordable method for estimating net energy expenditure (EE) in children performing activities at high altitude. A regression-based method predicts net oxygen consumption (VO(2)) from net heart rate (HR) along with several covariates. The method is atypical in that, the "net" measures are taken as the difference between exercise and resting VO(2) (DeltaVO(2)) and the difference between exercise and resting HR (DeltaHR); DeltaVO(2) partially corrects for resting metabolic rate and for posture, and DeltaHR controls for inter-individual variation in physiology and for posture.

Effect of high altitude on protein metabolism in Bolivian children.

In Bolivia, malnutrition in children is a major health problem that may be caused by inadequate protein, energy, and micronutrient intake; exposure to bacterial and parasitic infections; and life in a multistress environment (high altitude, cold, cosmic radiation, low ambient humidity). However, no data on protein absorption and utilization at high altitude were available. Therefore, we evaluated the effect of altitude on protein metabolism in Bolivian children.

Salivary progesterone levels and rate of ovulation are significantly lower in poorer than in better-off urban-dwelling Bolivian women.

Background: Agriculturalists in less-developed countries (LDC) have lower progesterone levels than urban industrialized populations. However, it is unknown if urban LDC populations are also relatively lower. We tested whether urban Bolivia samples-poorer (Bol-p) and better-off (Bol-b)-have lower progesterone than a Chicago (USA) sample, and whether progesterone and rate of ovulation are lower in Bol-p than in Bol-b.

Pulmonary gas exchange and acid-base state at 5,260 m in high-altitude Bolivians and acclimatized lowlanders.

Pulmonary gas exchange and acid-base state were compared in nine Danish lowlanders (L) acclimatized to 5,260 m for 9 wk and seven native Bolivian residents (N) of La Paz (altitude 3,600-4,100 m) brought acutely to this altitude. We evaluated normalcy of arterial pH and assessed pulmonary gas exchange and acid-base balance at rest and during peak exercise when breathing room air and 55% O2. Despite 9 wk at 5,260 m and considerable renal bicarbonate excretion (arterial plasma HCO3- concentration = 15.

Dopaminergic metabolism in carotid bodies and high-altitude acclimatization in female rats.

We tested the hypothesis that ovarian steroids stimulate breathing through a dopaminergic mechanism in the carotid bodies. In ovariectomized female rats raised at sea level, domperidone, a peripheral D2-receptor antagonist, increased ventilation in normoxia (minute ventilation = +55%) and acute hypoxia (+32%). This effect disappeared after 10 daily injections of ovarian steroids (progesterone + estradiol).

Effect of menstrual cycle phase on exercise performance of high-altitude native women at 3600 m.

At sea level normally menstruating women show increased ventilation (VE) and hemodynamic changes due to increased progesterone (P) and estrogen (E2) levels during the mid-luteal (L) compared to the mid-follicular (F) phase of the ovarian cycle. Such changes may affect maximal exercise performance. This repeated-measures, randomized study, conducted at 3600 m, tests the hypothesis that a P-mediated increase in VE increases maximal oxygen consumption (V(O(2)max)) during the L phase relative to the F phase in Bolivian women, either born and raised at high altitude (HA), or resident at HA since early childhood.

Effect of developmental and ancestral high altitude exposure on chest morphology and pulmonary function in Andean and European/North American natives.

Chest depth, chest width, forced vital capacity (FVC), and forced expiratory volume (FEV1) were measured in 170 adult males differing by ancestral (genetic) and developmental exposure to high altitude (HA). A complete migrant study design was used to study HA natives (Aymara/Quechua ancestry, n = 88) and low altitude (LA) natives (European/North American ancestry, n = 82) at both altitude (La Paz, Bolivia, 3,600 m) and near sea level (Santa Cruz, Bolivia, 420 m). HAN and LAN migrant groups were classified as: N(th) generation migrants, born and raised in a non-native environment; child migrants who migrated during the period of growth and maturation (0-18 yrs); and adult migrants who migrated after 18 years of age.

Coca chewing among high altitude natives: Work and muscular efficiencies of nonhabitual chewers.

The leaves of the coca plant (Erythroxylum sp.) have long been chewed by natives of the highland Andes. Folk belief is that the mild stimulant effect is indispensable as an ergogenic aid for strenuous work activities in a high altitude environment.