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. 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.

OBJETIVOS: En poblaciones no industrializadas y de bajos ingresos, las reservas adiposas pueden servir como un valioso amortiguador frente a condiciones duras como la escasez estacional de alimentos. Sin embargo, estas reservas pueden tener un coste debido a la producción de citoquinas proinflamatorias por parte de los adipocitos; la inflamación se asocia a un mayor riesgo de enfermedades cardiometabólicas en etapas posteriores de la vida. La teoría de la historia vital postula que, especialmente en poblaciones con una elevada mortalidad juvenil, una mayor adiposidad puede ser ventajosa si sus beneficios en los primeros años de vida compensan sus costes posteriores. Se sabe relativamente poco sobre la concentración de proteína C reactiva (PCR; un biomarcador de inflamación) de los adolescentes. Investigamos la PCR y sus asociaciones con varios predictores hipotéticos en adolescentes de una comunidad andina periurbana económicamente diversa. MÉTODOS: Se midió la PCR en muestras de sangre seca y se recogieron datos sobre antropometría, enfermedades, nivel socioeconómico (NSE) y menarquia en 59 mujeres y 40 varones adolescentes («alteños¼, 11,0­14,9 años de edad) con signos vitales normales en El Alto, Bolivia (~4150m amsl). Usamos el método LMS de Cole para estandarizar todos los parámetros antropométricos para sexo y edad, y análisis de componentes principales para construir una variable «factor de grasa¼ cargada en estos puntajes z­estandarizados. Se utilizó la regresión lineal múltiple para evaluar la influencia del factor grasa y otros posibles predictores en el rango de la PCR. RESULTADOS: En comparación con una referencia nacional boliviana de crecimiento, los alteños eran, en promedio, más bajos y más delgados; sólo el 6% estaban clasificados con sobrepeso y ninguno era obeso. Las chicas premenárquicos eran, en promedio, más delgados que las chicas postmenárquicos. El modelo de regresión que mejor se ajustaba explicaba el 24% de la varianza en el rango de PCR. Observamos una nueva asociación entre la adiposidad y la PCR. Cuando el factor adiposidad es >0, el rango de la PCR aumenta linealmente con el factor adiposidad. Cuando el factor adiposidad es <0, la PCR no varía con el factor adiposidad. Estos patrones sugieren que los Alteños más delgados mantienen una concentración mínima de PCR independiente del factor adiposidad, mientras que la PCR de los Alteños más gordos (menos delgados) aumenta con el factor adiposidad. Además, existe una mayor variación en el rango de la PCR en los adolescentes más delgados que en los más gordos. El autoinforme de una enfermedad actual en niños y niñas premenárquicas se asoció con una PCR significativamente más alta. La ausencia de una asociación significativa entre la enfermedad actual y la PCR en las chicas postmenárquicas puede reflejar confusión por cambios en la PCR durante el ciclo menstrual. Manteniendo constantes todos los demás factores predictivos, la PCR aumentó con el incremento del nivel socioeconómico. En las niñas, el aumento de la estatura se asoció a una disminución de la PCR, lo que sugiere que las niñas favorecen la inversión en crecimiento y maduración frente a la inversión en respuestas inmunitarias inflamatorias a corto plazo. En los chicos, no se observó una relación significativa entre la estatura y la PCR. La baja estatura y la delgadez de estos adolescentes sugieren que pueden estar invirtiendo en defensas humorales a más largo plazo (por ejemplo, anticuerpos contra helmintos), pero esta hipótesis requiere más estudios. CONCLUSIONES: La alta tasa de retraso en el crecimiento y la ausencia de obesidad de los alteños sugieren un estrés crónico, presumiblemente multifactorial. Muchas familias carecen de alimentos nutritivos suficientes, agua potable, alcantarillado adecuado y atención sanitaria. Es probable que las reservas adiposas amortigüen algunos de estos factores de estrés y confieran un beneficio neto a lo largo de la vida (la reducción de la mortalidad juvenil puede compensar cualquier aumento del riesgo de enfermedades cardiometabólicas en etapas posteriores de la vida). Sin embargo, estas compensaciones tienen un coste para los individuos y las sociedades. Reducir los riesgos de patógenos y mejorar la capacidad de los habitantes del altiplano para acceder sistemáticamente a agua limpia y a alimentos sanos suficientes y asequibles probablemente reportaría beneficios para la salud a lo largo de toda la vida.

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. However, assumptions persist regarding the extent and normalcy of variation in other cycle biomarkers. The processes of judging which phenotypic variants are "normal" is context dependent. In everyday life, normal is that which is most commonly seen. In biomedicine normal is often defined as an arbitrarily bounded portion of the phenotype's distribution about its statistical mean. Standards thus defined in one population are problematic when applied to other populations; population specific standards may also be suspect. Rather, recognizing normal female reproductive biology in diverse human populations requires specific knowledge of proximate mechanisms and functional context. Such efforts should be grounded in an empirical assessment of phenotypic variability. We tested hypotheses regarding cycle biomarker variability in women from a wealthy industrialized population (Germany) and a resource-limited rural agropastoral population (Bolivia). Ovulatory cycles in both samples displayed marked but nonetheless comparable variability in all cycle biomarkers and similar means/medians for cycle and phase lengths. Notably, cycle and phase lengths are poor predictors of mid-luteal progesterone concentrations. These patterns suggest that global and local statistical criteria for "normal" cycles would be difficult to define. A more productive approach involves elucidating the causes of natural variation in ovarian cycling and its consequences for reproductive success and women's health.

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. RESULTS: At baseline, haemoglobin concentration [Hb] and Hbmass were higher in Bolivians (mean ± SD; 18.2 ± 1.0 g/dL, 12.8 ± 0.8 g/kg) than Australians (15.0 ± 0.9 g/dL, 11.6 ± 0.7 g/kg; both p ≤ 0.001). Near sea-level, [Hb] of Bolivians decreased to 16.6 ± 0.9 g/dL, but normalised upon return to 3600 m; Hbmass was constant regardless of altitude. In Australians, [Hb] increased after 12 days at 3600 m to 17.3 ± 1.0 g/dL; Hbmass increased by 3.0 ± 2.7% (p ≤ 0.01). BV decreased in both teams at altitude by ∼400 mL. Arterial partial pressure for oxygen (PaO2), Hb-sO2 and CaO2 of both teams decreased within 2 h of arrival at 3600 m (p ≤ 0.001) but increased over the following days, with CaO2 overcompensated in Australians (+1.7 ± 1.2 mL/100 mL; p ≤ 0.001). Yo-YoIR1 was lower on the 3rd versus 10th day at altitude and was significantly related to CaO2. CONCLUSIONS: The marked drop in PaO2 and CaO2 observed after ascent does not support the 'fly-in, fly-out' approach for soccer teams to play immediately after arrival at altitude. Although short-term acclimatisation was sufficient for Australians to stabilise their CaO2 (mostly due to loss of plasma volume), 12 days appears insufficient to reach chronic levels of adaption.

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. METHODS: A U20 Bolivian team ('The Strongest' from La Paz, n=19) played a series of five games against a U17 team from sea level in Australia (The Joeys, n=20). 2 games were played near sea level (Santa Cruz 430 m) over 5 days and then three games were played in La Paz over the next 12 days. Measures were (1) game and training running performance--including global positioning system (GPS) data on distance travelled and velocity of movement; (2) blood--including haemoglobin mass, blood volume, blood gases and acid-base status; (3) acclimatisation--including resting heart rate variability, perceived altitude sickness, as well as heart rate and perceived exertion responses to a submaximal running test; and (4) sleep patterns. CONCLUSIONS: Pivotal to the success of the project were the strong professional networks of the collaborators, with most exceeding 10 years, the links of several of the researchers to soccer federations, as well as the interest and support of the two head coaches.

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), 11.0-14.9 years old in 2003, were compared between households (economic status assessed by parental occupations); to one urban and two rural samples collected in 1983/1998/1977, respectively; and to the WHO growth reference, a representative sample of Bolivian children (MESA), and a region-wide sample of high-altitude Peruvian children (Puno). Results: Female Alteños' growth was positively associated with household and maternal income indices. Alteños' height averaged ∼0.8SD/∼0.6SD/∼2SDs greater than adolescents' height in urban and rural communities measured in 1983/1998/1977, respectively. Overweight prevalence was comparable to the WHO, and lower than MESA and Puno, references. Stunting was 8.5/2.5/0.5 times WHO/MESA/Puno samples, respectively. Conclusions/Implications: Both peri-urban conditions and temporal trends contributed to gains in Alteños' growth. Rural out-migration can alleviate migrants' poverty, partly because of more diverse economic options in urbanized communities, especially for women. Nonetheless, Alteños averaged below WHO and MESA height and weight medians. Evolved biological adaptations to environmental challenges, and the consequent variability in growth trajectories, favor using multiple growth references. Growth monitoring should be informed by community- and household-level studies to detect and understand local factors causing or alleviating health disparities.

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. Anovulation rate (AR) was higher during the most arduous seasons and in older women. Breastfeeding and indicators of social status and living conditions did not significantly influence either risk of EPL or AR. Averaged over the year, anovulation occurred in about 1/4 of the cycles and EPL occurred in about 1/3 of the conceptions. This is the first evidence of seasonality of EPL in a non-industrialized population, and the first to demonstrate a relationship between economic activities and EPL. These findings suggest that both anovulation and EPL are potential mechanisms for modulating reproductive effort; such "failures" may also be nonadaptive consequences of conditions hostile to a successful pregnancy. In either case, variation in EPL risk associated with different subsistence activities can be expected to influence fertility levels and birth seasonality in both contemporary and past human populations. These consequences of variability in the risk of EPL can impact efforts to understand the sources of variation in reproductive success.

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. For each pair of salivary T(AM)/T(PM) samples (collected in a approximately 12-h period), circadian rhythm was considered classic (C(CLASSIC)) if T(AM) > 110%T(PM), reverse (C(REVERSE)) if T(PM) > 110%T(AM), and flat (C(FLAT)) otherwise. We tested the hypotheses that mean T(AM) > mean T(PM) and that mean T(LW) < mean T(OTHER) (LW = late winter, OTHER = other seasons). In Study A, of 115 T(PM)-T(AM) pairs, 51% = C(CLASSIC), 39% = C(REVERSE), 10% = C(FLAT); in Study B, of 184 T(AM)-T(PM) pairs, 55% = C(CLASSIC), 33% = C(REVERSE), 12% = C(FLAT). Based on fitting linear mixed models, in both studies T(OTHER-AM) > T(OTHER-PM) (A: P = 0.035, B: P = 0.0005) and T(OTHER-AM) > T(LW-AM) (A: P = 0.054, B: P = 0.007); T(PM) did not vary seasonally, and T diurnality was not significant during late winter. T diurnality varied substantially between days within an individual, between individuals and between seasons, but neither T levels nor diurnality varied with age. These patterns may reflect the seasonally varying but unscheduled, life-long, strenuous physical labor that typifies many non-industrialized economies. These results also suggest that single morning samples may substantially underestimate peak circulating T for an individual and, most importantly, that exogenous signals may moderate diurnality and the trajectory of age-related change in the male gonadal axis.

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. We therefore measured systolic pulmonary-artery pressure (Doppler chocardiography) and exhaled nitric oxide (NO) in 34 healthy, middle-aged Bolivian high altitude natives and in 34 age- and sex-matched, well-acclimatized Caucasian low altitude natives living at high altitude (3600 m). The mean+/-SD systolic right ventricular to right atrial pressure gradient (24.3+/-5.9 vs. 24.7+/-4.9 mmHg) and exhaled NO (19.2+/-7.2 vs. 22.5+/-9.5 ppb) were similar in Bolivians and Caucasians. There was no relationship between pulmonary-artery pressure and respiratory NO in the two groups. These findings provide no evidence that Bolivian high altitude natives are better protected from hypoxic pulmonary hypertension than Caucasian low altitude natives and suggest that attenuation of pulmonary hypertension by increased respiratory NO synthesis may not represent a universal adaptation pattern in highaltitude populations.

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). PARTICIPANTS: One hundred eighty-four co-sleeping mother-infant pairs (infant age 22-730 days). MEASUREMENTS: Breastfeeding frequency, and retiring and rising times for 885 48-hour observation periods. RESULTS: Maternal sleep duration covaried with darkness duration. Sleep duration was shorter in those with access to electricity (ie, living nearer to town) than those without access (more distant homesteads). Night breastfeeding rate was fairly steady until it began to decline after the first year postpartum. At a given infant age, higher night breastfeeding rates were associated with less maternal sleep. As their infants aged, mothers without electricity slept more, whereas mothers with access slept less. CONCLUSIONS: During the first year postpartum, more frequent night nursing shortens maternal sleep more than any other predictor variable. For older infants, the effect of night nursing diminishes, and even modest "modernization" (eg, access to electricity) is associated with shorter maternal sleep.

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. RESULTS: Estimated anemia prevalence among these non-pregnant women was 50% higher than the national average. Despite holding conceptualizations of anemia generally aligned with biomedical concepts, only 40% of anemic women attempted to obtain iron supplements from the health center. Town residents were about twice as likely to attempt to purchase pills as outside-town residents. Town women who were concurrently breastfeeding and menstruating, considered anemia most serious for women, and considered family health the shared responsibility of spouses were most likely to decide to purchase iron pills. Age, education, or native language did not negatively influence this health care behavior. CONCLUSIONS: Securing iron supplements involves individual trade-offs in the allocation of time, cost and effort. Nonetheless, suitably tailored programs can potentially harness local perceptions in the service of reducing anemia. Because of their comparatively high motivation to obtain iron supplements, targeting concurrently breastfeeding and menstruating women could have a positive cascade effect such that these women continue attending to their iron needs once they stop breastfeeding and if they become pregnant again. Because a sense of shared responsibility for family health appears to encourage women to attend to their own health, programs for women could involve their spouses. Complementing centralized availability, biomedical and traditional healers could distribute iron supplements on rotating visits to outlying areas and/or at highly attended weekly markets.

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. The calculated optimal hemoglobin concentration of 14.7 g/dL for resting men in the Andes is discussed as theoretical and not applicable in real life. The most frequent congenital and acquired heart diseases are discussed, such as patent ductus, atrial septum defect, ventricle septum defect among congenital heart diseases and the still very frequent rheumatic valve cardiopathies and Chagas disease as acquired cardiopathies. Among the typical acquired heart diseases of the high altitude dweller, special attention is given to chronic cor pulmonale as a consequence of severe CMS with pulmonary hypertension.

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 = 15.1 meq/l), resting arterial pH in L was 7.48 +/- 0.007 (significantly greater than 7.40). On the other hand, arterial pH in N was only 7.43 +/- 0.004 (despite arterial O2 saturation of 77%) after ascent from 3,600-4,100 to 5,260 m in 2 h. Maximal power output was similar in the two groups breathing air, whereas on 55% O2 only L showed a significant increase. During exercise in air, arterial PCO2 was 8 Torr lower in L than in N (P < 0.001), yet PO2 was the same such that, at maximal O2 uptake, alveolar-arterial PO2 difference was lower in N (5.3 +/- 1.3 Torr) than in L (10.5 +/- 0.8 Torr), P = 0.004. Calculated O2 diffusing capacity was 40% higher in N than in L and, if referenced to maximal hyperoxic work, capacity was 73% greater in N. Buffering of lactic acid was greater in N, with 20% less increase in base deficit per millimole per liter rise in lactate. These data show in L persistent alkalosis even after 9 wk at 5,260 m. In N, the data show 1) insignificant reduction in exercise capacity when breathing air at 5,260 m compared with breathing 55% O2; 2) very little ventilatory response to acute hypoxemia (judged by arterial pH and arterial PCO2 responses to hyperoxia); 3) during exercise, greater pulmonary diffusing capacity than in L, allowing maintenance of arterial PO2 despite lower ventilation; and 4) better buffering of lactic acid. These results support and extend similar observations concerning adaptation in lung function in these and other high-altitude native groups previously performed at much lower altitudes.

Skin reflectance of children and young adults of Aymara ancestry.

The skin reflectance of 556 Andean Indians of Aymara ancestry (305 males, 251 females; 10.0-29.9 yr) residing in La Paz, Bolivia (average altitude of about 3,600 m) is described. Reflectances were measured at three wavelengths (425 nm, 545 nm, and 685 nm) on two different sites, the medial surface of the upper arm and forehead. Males tended to be significantly darker than females on both the upper arm and forehead (P < .05). Female Aymara tended to lighten significantly in skin color with age on both the upper arm and forehead, while males tended to lighten significantly with age only on the upper arm (P < .05). The results of comparisons between three categories based on paternal and maternal surnames (two Aymara surnames, one Aymara and one Spanish surname, and two Spanish surnames) were consistent with the hypothesis that the possession of Spanish surnames is positively related to the degree of European admixture in urban Aymara. However, the extent of admixture within each surname category may differ between rural and urban Aymara, making classification by surnames problematic for rural-urban comparisons.

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. This study explored the exercise responses of 23 nonhabitual coca chewing males who were asked to pedal a bicycle ergometer through a series of submaximal and maximal workloads both with and without coca chewing. The protocol of the exercise test was specifically designed to allow for the determination of work and muscular efficiencies during to submaximal work. The subjects showed no differences between the coca and control work protocols for VO2 max (1/min), VCO2 max (1/min), or maximal work output (watts). Further, there were no differences between coca and control work protocols in oxygen saturation (%), pulmonary ventilation (1/min), or respiratory exchange ratio (VCO2 /VO2 ) at any level of work. Coca chewing caused subjects to have a higher heart rate (bpm) and lower oxygen pulse (ml/beat) for most submaximal workloads and higher ventilatory equivalents (VE/VO2 and VE/VCO2 ) above 50% of VO2 max. Although there was a tendency for higher gross efficiencies (GE) during the coca exercise test at lower relative work levels, between 30-40% of the VO2 max, this difference did not reach significance. Mean net efficiency (NE) was higher (P=0.018) at a relative work level of ∼32% of the VO2 max for exercise with coca (23.2% vs. 20.8%). This difference was not apparent at any other work level. The mean delta efficiency (DE) was significantly lower (P = 0.012) for exercise with coca (26.7%) than for exercise without coca (28.2%). These efficiency differences suggest a muscle metabolic effect for coca chewing at low workloads whereby less oxygen is consumed by the muscle to perform a given work task. Howeve, given the difficulty of interpreting efficiency values, it is not entirely clear if the differences are indicative of a work performance benefit for coca chewing. © 1995 Wiley-Liss, Inc.

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. Chest depth, FVC, and FEV1 measures were larger with increasing developmental exposure in both HAN migrants at LA and LAN migrants at HA. Developmental responses were similar between HAN and LAN groups. FVC and FEV1 measures were larger in HANs vs LANs born and raised at HA to suggest a genetic effect, but were similar in HANs and LANs born and raised at LA. The similarity of HAN and LAN groups at LA suggests that the genetic potential for larger lung volumes at HA depends upon developmental exposure to HA. Additional data for females (HANs at HA, n = 20, and LAN adult migrants to HA, n = 17) show similar differences as those shown between male HAN and LAN groups. Am. J. Hum. Biol. 11:383-395, 1999. Copyright 1999 Wiley-Liss, Inc.

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. European), altitude of birth (highlands vs. lowlands), and the altitude where tested (420, 3600, 3850 m). This design allows partitioning of ancestral (i.e., genetic) and developmental effects. To minimize measurement error, subjects were given two submaximal exercise tests on a cycle ergometer (on separate days). Each test consisted of four 5-min work bouts (levels), each separated by a 5-min rest period. For all groups, the oxygen consumption (V(O2))-work rate relationship was not different from the sea-level reference. Gross and net efficiencies (GE and NE) were not different between groups at any work level, with the exception of European men born in the lowlands and acclimatized and tested at 3600 m. These men showed slightly lower V(O2) at high work output, but this may be due to a nonsteady-state V(O2) kinetic, rather than to an altered steady-state V(O2)-work rate relationship per se. There were no significant group differences in delta efficiency (DE). In sum, these results provide no support for the hypothesis of energetic advantage during submaximal work in Andean HA natives. A review and analysis of the literature suggest that the same is true for HA natives in the Himalayas.

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. We measured protein utilization using leucine labeled with a stable isotope ((13)C) in two groups of healthy prepubertal children matched for age. Group 1 (n = 10) was examined at high altitude (HA) in La Paz (3600 m), and group 2 (n = 10) at low altitude (LA) in Santa Cruz (420 m). The nutritional status did not differ between groups but, as was to be expected, the HA group had higher hemoglobin concentration than the LA group. The children consumed casein that was intrinsically labeled with L-(1-(13)C) leucine and expired (13)CO(2) was analyzed. Samples of expired air were measured by isotope ratio mass spectrometer in Clermont-Ferrand. It was found that cumulative leucine oxidation ((13)CO(2)) at 300 min after ingestion was 19.7 +/- 4.9% at HA and 25.2 +/- 3.2% at LA. These results showed that protein absorption and/or utilization is significantly affected by altitude.

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. Drawing upon our longitudinal study of reproductive functioning among rural Bolivians (Project Reproduction and Ecology in Provincia Aroma (REPA)), we propose an evolutionary model to explain variation in certain aspects of women's reproductive health. Our findings suggest new avenues of inquiry into the determinants of reproductive health and have implications for improving the well-being of women worldwide.

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. METHODS: We estimated pulmonary artery pressure by using echocardiography at rest and during mild bicycle exercise at 50 W in 30 male patients with CMS and 32 age-matched, healthy control subjects who were born and living at an altitude of 3,600 m. RESULTS: The modest, albeit significant difference of the systolic right-ventricular-to-right-atrial pressure gradient between patients with CMS and controls at rest (30.3 +/- 8.0 vs 25.4 +/- 4.5 mm Hg, P 5 .002) became more than three times larger during mild bicycle exercise (56.4 +/- 19.0 vs 39.8 +/- 8.0 mm Hg, P < .001). CONCLUSIONS: Measurements of pulmonary artery pressure at rest greatly underestimate pulmonary artery pressure during daily activity in patients with CMS. The marked pulmonary hypertension during mild exercise associated with daily activity may explain why this problem is a leading cause of morbidity and mortality in patients with CMS.