Social context and psychosocial influences on blood pressure among American Samoans

Disentangling social, environmental, and zoonotic transmission pathways of a gastrointestinal protozoan (Blastocystis spp.) in northeast Madagascar

OBJECTIVES

Understanding disease transmission is a fundamental challenge in ecology. We used transmission potential networks to investigate whether a gastrointestinal protozoan (Blastocystis spp.) is spread through social, environmental, and/or zoonotic pathways in rural northeast Madagascar.

MATERIALS AND METHODS

We obtained survey data, household GPS coordinates, and fecal samples from 804 participants. Surveys inquired about social contacts, agricultural activity, and sociodemographic characteristics. Fecal samples were screened for Blastocystis using DNA metabarcoding. We also tested 133 domesticated animals for Blastocystis. We used network autocorrelation models and permutation tests (network k-test) to determine whether networks reflecting different transmission pathways predicted infection.

RESULTS

We identified six distinct Blastocystis subtypes among study participants and their domesticated animals. Among the 804 human participants, 74% (n = 598) were positive for at least one Blastocystis subtype. Close proximity to infected households was the most informative predictor of infection with any subtype (model averaged OR [95% CI]: 1.56 [1.33-1.82]), and spending free time with infected participants was not an informative predictor of infection (model averaged OR [95% CI]: 0.95 [0.82-1.10]). No human participant was infected with the same subtype as the domesticated animals they owned.

DISCUSSION

Our findings suggest that Blastocystis is most likely spread through environmental pathways within villages, rather than through social or animal contact. The most likely mechanisms involve fecal contamination of the environment by infected individuals or shared food and water sources. These findings shed new light on human-pathogen ecology and mechanisms for reducing disease transmission in rural, low-income settings.

Age variation in blood pressure: Rural-urban and sex differences among the Hmar adults of Manipur, Northeast India

BACKGROUND

Increase in blood pressure (BP) is thought to be an unavoidable consequence of ageing but in secluded communities and in rural areas this is not the case.

AIMS

The present study aims to examine blood pressure response with age across place of residence and sex; the prevalence of hypertension in relation to place of residence and sex; and to find out the relative importance of biological and behavioural factors as risk factors for hypertension among the Hmar adults (17 to 70 years of age) of Manipur, Northeast India.

MATERIALS AND METHODS

A cross-sectional sample was collected on 1207 Hmars adults residing in rural and urban settings in Manipur, Northeast India. Demographic data, blood pressure, height, weight and behavioural factors were collected.

RESULTS

Blood pressure significantly increases with an increasing age and this trend is more pronounced in urban settings compared to rural settings. The overall prevalence of hypertension in the present study is about 21 per cent. Urban Hmar males, rural and urban Hmar females who are ≥ 45 years of age show significantly higher risk of developing hypertension compared to their counterparts who are < 45 years of age, but the same is not observed in Hmar males from rural areas. Males show significantly higher odds of developing hypertension compared to females in both the settings. Obesity is the strongest predictor of hypertension in both the place of residence and sexes.

DISCUSSION AND CONCLUSION

The present study confirms that population blood pressure does not show a marked increase with increasing age in traditional/rural areas which is clearly perceptible in Hmar men. It also strengthen the case that urban residence, men, increasing age and overweight and/or obese significantly increases the odds of developing hypertension.

Pathogen disgust sensitivity protects against infection in a high pathogen environment

Disgust is hypothesized to be an evolved emotion that functions to regulate the avoidance of pathogen-related stimuli and behaviors. Individuals with higher pathogen disgust sensitivity (PDS) are predicted to be exposed to and thus infected by fewer pathogens, though no studies have tested this directly. Furthermore, PDS is hypothesized to be locally calibrated to the types of pathogens normally encountered and the fitness-related costs and benefits of infection and avoidance. Market integration (the degree of production for and consumption from market-based economies) influences the relative costs/benefits of pathogen exposure and avoidance through sanitation, hygiene, and lifestyle changes, and is thus predicted to affect PDS. Here, we examine the function of PDS in disease avoidance, its environmental calibration, and its socioecological variation by examining associations among PDS, market-related lifestyle factors, and measures of bacterial, viral, and macroparasitic infection at the individual, household, and community levels. Data were collected among 75 participants (ages 5 to 59 y) from 28 households in three Ecuadorian Shuar communities characterized by subsistence-based lifestyles and high pathogen burden, but experiencing rapid market integration. As predicted, we found strong negative associations between PDS and biomarkers of immune response to viral/bacterial infection, and weaker associations between PDS and measures of macroparasite infection, apparently mediated by market integration-related differences. We provide support for the previously untested hypothesis that PDS is negatively associated with infection, and document variation in PDS indicative of calibration to local socioeconomic conditions. More broadly, findings highlight the importance of evolved psychological mechanisms in human health outcomes.

Biocultural approaches to transgender and gender diverse experience and health: Integrating biomarkers and advancing gender/sex research

Transgender and gender diverse (TGD) people are increasingly visible in U.S. communities and in national media. With this increased visibility, access to gender affirming healthcare is also on the rise, particularly for urban youth. Political backlash and entrenchment in a gender binary, however, continue to marginalize TGD people, increasing risk for health disparities. The 2016 National Institute of Health recognition of sexual and gender minority people as a health disparities population increases available funding for much-needed research. In this article, we speak to the need for a biocultural human biology of gender/sex diversity by delineating factors that influence physiological functioning, mental health, and physical health of TGD people. We propose that many of these factors can best be investigated with minimally invasively collected biomarker samples (MICBS) and discuss how to integrate MICBS into research inclusive of TGD people. Research use of MICBS among TGD people remains limited, and wider use could enable essential biological and health data to be collected from a population often excluded from research. We provide a broad overview of terminology and current literature, point to key research questions, and address potential challenges researchers might face when aiming to integrate MCIBS in research inclusive of transgender and gender diverse people. We argue that, when used effectively, MICBS can enhance human biologists' ability to empirically measure physiology and health-related outcomes and enable more accurate identification of pathways linking human experience, embodiment, and health.

Market integration and soil-transmitted helminth infection among the Shuar of Amazonian Ecuador

BACKGROUND

Soil-transmitted helminth (STH) infections have many negative health outcomes (e.g., diarrhea, nutritional deficiencies) that can also exacerbate poverty. These infections are generally highest among low-income populations, many of which are also undergoing market integration (MI; increased participation in a market-based economy). Yet the direct impact of MI-related social and environmental changes on STH infection patterns is poorly understood, making it unclear which lifestyle factors should be targeted to better control disease spread. This cross-sectional study examines if household infrastructure associated with greater MI is associated with lower STH burdens among Indigenous Ecuadorian Shuar.

METHODS

Kato-Katz fecal smears were used to determine STH infection status and intensity (n = 620 participants; 308 females, 312 males, aged 6 months-86 years); Ascaris lumbricoides (ascarid) and Trichuris trichiura (whipworm) were the primary infection types detected. Structured interviews assessing lifestyle patterns (e.g., measures of household infrastructure) measured participant MI. Multilevel regression analyses and zero-inflated negative binomial regression models tested associations between MI measures and STH infection status or intensity, controlling for individual and community characteristics.

RESULTS

Participants residing in more market-integrated households exhibited lower infection rates and intensities than those in less market integrated households. Parasite infection status and T. trichiura infection intensity were lower among participants living in houses with wood floors than those with dirt floors, while individuals using well or piped water from a spring exhibited lower A. lumbricoides infection intensities compared to those using river or stream water. Unexpectedly, latrine type was not significantly related to STH infection status or intensity. These results suggest that sources of exposure differ between the two helminth species.

CONCLUSIONS

This study documents associations between household measures and STH infection among an Indigenous population undergoing rapid MI. These findings can help healthcare programs better target interventions and reduce STH exposure among at-risk populations.

Heterogeneous effects of market integration on sub-adult body size and nutritional status among the Shuar of Amazonian Ecuador

BACKGROUND

Market integration (MI)-increasing production for and consumption from a market-based economy-is drastically altering traditional ways of life and environmental conditions among indigenous Amazonian peoples. The effects of MI on the biology and health of Amazonian children and adolescents, however, remain unclear.

AIM

This study examines the impact of MI on sub-adult body size and nutritional status at the population, regional and household levels among the Shuar of Amazonian Ecuador.

SUBJECTS AND METHODS

Anthropometric data were collected between 2005-2014 from 2164 Shuar (aged 2-19 years) living in two geographic regions differing in general degree of MI. High-resolution household economic, lifestyle and dietary data were collected from a sub-sample of 631 participants. Analyses were performed to investigate relationships between body size and year of data collection, region and specific aspects of household MI.

RESULTS

Results from temporal and regional analyses suggest that MI has a significant and overall positive impact on Shuar body size and nutritional status. However, household-level results exhibit nuanced and heterogeneous specific effects of MI underlying these overarching relationships.

CONCLUSION

This study provides novel insight into the complex socio-ecological pathways linking MI, physical growth and health among the Shuar and other indigenous Amazonian populations.

Soil-transmitted helminth prevalence and infection intensity among geographically and economically distinct Shuar communities in the Ecuadorian Amazon

Soil-transmitted helminth (STH) infections can result in a variety of negative health outcomes (e.g., diarrhea, nutritional deficiencies). Market integration (MI; participation in market-based economies) has been suggested to alter levels of STH exposure due to associated changes in diet, sanitation, and behavior, but the effects are complicated and not well understood. Some effects of economic development result in decreased exposure to certain pathogens, and other factors can lead to higher pathogen exposure. With geographic location used as a proxy, the present study investigates the effects of economic development on parasite load among an indigenous population at multiple points along the spectrum of MI. This research has many implications for public health, including an increased understanding of how social and economic changes alter disease risk around the world and how changing parasite load affects other health outcomes (i.e., allergy, autoimmunity). Specifically, this study examines the prevalence of intestinal helminths among the Shuar, an indigenous group in the Morona-Santiago region of Ecuador, from 2 geographically/economically separated areas, with the following objectives: (1) report STH infection prevalence and intensity among Shuar; (2) explore STH infection prevalence and intensity as it relates to age distribution in the Shuar population; (3) compare STH infection patterns in geographically and economically separated Shuar communities at different levels of MI. Kato-Katz thick smears were made from fresh stool samples and examined to determine STH presence/intensity. Results indicate that 65% of the 211 participants were infected with at least 1 STH. Twenty-five percent of the sample had coinfections with at least 2 species of helminth. Infection was more common among juveniles (<15 yr) than adults. Infection prevalence and intensity was highest among more isolated communities with less market access. This study documents preliminary associations between STH infection and exposure to MI, with implications for public health research and interventions.

Seasonal variation in basal metabolic rates among the Yakut (Sakha) of Northeastern Siberia

OBJECTIVES

Previous research has shown that indigenous circumpolar populations have elevated basal metabolic rates (BMRs), yet few studies have explored whether metabolic rates increase during the winter. This study addresses this gap by examining seasonal variation in BMR and its associations with thyroid function and lifestyle factors among the Yakut (Sakha) of Siberia.

METHODS

Anthropometric dimensions, BMR, and thyroid hormone levels (free triiodothyronine [fT3], free thyroxine [fT4], thyroid-stimulating hormone [TSH]) were measured on two occasions (July/August, 2009 and January 2011) on a sample of 94 Yakut (Sakha) adults (35 men, 59 women) from the rural village of Berdygestiakh, Sakha Republic, Russia.

RESULTS

Seasonal changes in BMR varied by age. Younger Yakut adults (19-49 years) showed significant elevations in winter-time BMR of 6% (P < 0.05), whereas older individuals (≥50 years) showed modest declines (2%; n.s.). Both younger and older Yakut men and women showed increased respiratory quotients during the winter. FT3 and fT4 levels significantly declined during the winter in both younger and older Yakut men and women (P < 0.05). Lifestyle factors were significant predictors of BMR variation, particularly among older men and women.

CONCLUSIONS

Among the Yakut, increased wintertime BMR was observed among younger but not older adults, whereas all adults showed sharp reductions in free thyroid hormone levels during the winter. Among men, greater participation in subsistence activities was associated with increased BMRs and greater fat oxidation. Among women, variation in food use had the strongest impact on metabolic function.

Impact of lifestyle changes on stress in a modernizing rural population in Hainan Island, China

OBJECTIVE

Little is known about inter-individual variation in psychological stress in modernizing rural populations in developing countries. The objective of this study was to investigate the association between Epstein-Barr virus (EBV) antibody titer, a biomarker of psychological stress, and lifestyle parameters in rural communities in Hainan Island, China.

METHODS

EBV antibody titer was measured in dried blood spot (DBS) samples collected from 240 adults living in rural communities in Hainan Island. Measures of two major lifestyle changes in rural areas of Hainan Island, i.e., diet and commercial goods possession, were examined by using information on the weekly frequency of pork consumption and monthly mobile phone fees. Both parameters were standardized to create two composite scores: a total affluence index (TAI--the sum of these scores), and an investment tendency index (ITI--the difference between them). Least-squares regression analysis was used to investigate the association between EBV antibody titer and these lifestyle parameters.

RESULTS

A positive association was found between the frequency f pork consumption and EBV antibody titer (P = 0.040), whereas a negative association was found between mobile phone fees and EBV antibody titer (P = 0.028). A negative association was also observed between ITI and EBV antibody titer (P = 0.002) after adjusting for the effect of TAI.

CONCLUSION

Psychological stress among local residents was linked to the type of lifestyle changes they had experienced, where the adoption of a more market-oriented lifestyle, irrespective of current affluence, was associated with less psychological stress.

Implications of market integration for cardiovascular and metabolic health among an indigenous Amazonian Ecuadorian population

BACKGROUND

Market integration (MI), the suite of social and cultural changes that occur with economic development, has been associated with negative health outcomes such as cardiovascular disease; however, key questions remain about how this transition manifests at the local level.

AIM

The present paper investigates the effects of MI on health among Shuar, an indigenous lowland Ecuadorian population, with the goal of better understanding the mechanisms responsible for this health transition.

SUBJECTS AND METHODS

This study examines associations between measures of MI and several dimensions of cardiovascular and metabolic health (fasting glucose, lipids [LDL, HDL and total cholesterol; triglycerides] and blood pressure) among 348 adults.

RESULTS

Overall, Shuar males and females have relatively favourable cardiovascular and metabolic health. Shuar who live closer to town have higher total (p < 0.001) and HDL cholesterol (p < 0.001), while Shuar in more remote regions have higher diastolic blood pressure (p = 0.007). HDL cholesterol is positively associated with consumption of market foods (r = 0.140; p = 0.045) and ownership of consumer products (r = 0.184; p = 0.029).

CONCLUSIONS

This study provides evidence that MI among Shuar is not a uniformly negative process but instead produces complex cardiovascular and metabolic health outcomes.

Diurnal cortisol rhythms among Latino immigrants in Oregon, USA

One of the most commonly used stress biomarkers is cortisol, a glucocorticoid hormone released by the adrenal glands that is central to the physiological stress response. Free cortisol can be measured in saliva and has been the biomarker of choice in stress studies measuring the function of the hypothalamic-pituitary-adrenal axis. Chronic psychosocial stress can lead to dysregulation of hypothalamic-pituitary-adrenal axis function and results in an abnormal diurnal cortisol profile. Little is known about objectively measured stress and health in Latino populations in the United States, yet this is likely an important factor in understanding health disparities that exist between Latinos and whites. The present study was designed to measure cortisol profiles among Latino immigrant farmworkers in Oregon (USA), and to compare quantitative and qualitative measures of stress in this population. Our results indicate that there were no sex differences in average cortisol AUCg (area under the curve with respect to the ground) over two days (AvgAUCg; males = 1.38, females = 1.60; P = 0.415). AUCg1 (Day 1 AUCg) and AvgAUCg were significantly negatively associated with age in men (P<0.05). AUCg1 was negatively associated with weight (P<0.05), waist circumference (P<0.01) and waist-to-stature ratio (P<0.05) in women, which is opposite of the expected relationship between cortisol and waist-to-stature ratio, possibly indicating hypothalamic-pituitary-adrenal axis dysregulation. Among men, more time in the United States and immigration to the United States at older ages predicted greater AvgAUCg. Among women, higher lifestyle incongruity was significantly related to greater AvgAUCg. Although preliminary, these results suggest that chronic psychosocial stress plays an important role in health risk in this population.

Associations between transition-specific stress experience, nocturnal decline in ambulatory blood pressure, and C-reactive protein levels among transgender men

OBJECTIVES

To characterize challenges experienced during stages of female-to-male sex transition and investigate associations between transition-specific measures of psychosocial stress, nocturnal decline in ambulatory blood pressure (amBP), and changes in C-reactive protein (CRP) levels.

METHODS

For this biocultural study, 65 healthy transmen who were using testosterone (T) therapy participated in interviews to assess transition-specific stress experience. They provided perceived stress scores, self-esteem scores, 24-h amBP measures, salivary samples for T levels, and a blood spot for CRP levels. Psychosocial stress was examined in relation to amBP and CRP using linear regression while adjusting for age, body mass index, and smoking.

RESULTS

There were no differences in mean levels of amBP in association with stage of transition. Men reporting stress associated with being "out" as transgender had significantly diminished nocturnal decline in systolic and diastolic amBP compared to men who did not report such stress. The associations remained significant when examined among men in stages 1 and 2 (≤ 3 years on T), but not among men in stage 3 (>3 years on T) of transition. Men reporting stress related to "passing" as someone born male had higher CRP levels than those who did not report such stress. The association remained significant when examined among men in stages 2 and 3 (>0.5-3 years on T).

CONCLUSION

Measures of stress that captured individuals' experiences of gender liminality were associated with diminished nocturnal decline in amBP and increased levels of CRP. There are significant differences between men grouped into different stages of the transition process.

Cultural consonance and body morphology: estimates with longitudinal data from an Amazonian society

Researchers have hypothesized that the degree to which an individual's actual behavior approximates the culturally valued lifestyle encoded in the dominant cultural model has consequences for physical and mental health. We contribute to this line of research by analyzing data from a longitudinal study composed of five annual surveys (2002-2006 inclusive) from 791 adults in one society of foragers-farmers in the Bolivian Amazon, the Tsimane'. We estimate the association between a standard measure of individual achievement of the cultural model, cultural consonance, and three indicators of body morphology. Drawing on research suggesting that in societies in the early stages of economic development an increase in socioeconomic status is associated with an increase in mean body mass, we expect to find a positive association between cultural consonance and three anthropometric measures. We found the expected positive association between cultural consonance and anthropometric measures-especially for men-only when using ordinary least square (OLS) regression models, but not when using fixed-effects regression models. The real magnitude of the association was low. The comparison of estimates from OLS and fixed-effect regression models suggests that previous findings on the effects of cultural consonance on body morphology using cross-sectional data should be read with caution because the association might be largely explained by fixed characteristics of individuals not accounted in OLS models.

Cultural consonance and psychological well-being. Estimates using longitudinal data from an Amazonian society

Researchers have hypothesized that the degree to which an individual's actual behavior approximates the culturally valued lifestyle encoded in the dominant cultural model has consequences for physical and mental health. We contribute to this line of research by analyzing data from a longitudinal study composed of five annual surveys (2002-2006 inclusive) of 791 adults in one society of foragers-farmers in the Bolivian Amazon, the Tsimane'. We estimate the association between a standard measure of individual achievement of the cultural model and (a) four indicators of psychological well-being (sadness, anger, fear and happiness) and (b) consumption of four potentially addictive substances (alcohol, cigarette, coca leaves and home-brewed beer) as indicators of stress behavior. After controlling for individual fixed effects, we found a negative association between individual achievement of the cultural model and psychological distress and a positive association between individual achievement of the cultural model and psychological well-being. Only the consumption of commercial alcohol bears the expected negative association with cultural consonance in material lifestyle, probably because the other substances analyzed have cultural values attached. Our work contributes to research on psychological health disparities by showing that a locally defined and culturally specific measure of lifestyle success is associated with psychological health.

Blood pressure and lifestyle on Saba, Netherlands Antilles

During the 20th century, infectious disease morbidity and mortality generally waned whereas chronic degenerative diseases posed a growing burden at the global level. The population on Saba, Netherlands Antilles has recently experienced such an epidemiologic transition, and hypertension was reported to be extraordinarily high, although no prevalences have been reported and relationships with lifestyle factors associated with rapid modernization have not been explored. In this study, a medical and demographic questionnaires, as well as body composition and blood pressure measures were collected from 278 Saban men and women aged 18-91 years. When age and sex adjusted, 48% of the population was hypertensive. Age, BMI, and Afro-Caribbean descent were all associated with higher blood pressures. In a second phase, 124 individuals of the 278 were invited to receive a longer questionnaire on individual exposure to modernizing influences such as travel and education. Higher blood pressure was associated with having lived in fewer different places in the past; those who stayed only on Saba or Statia had higher blood pressures than those who had also lived in more modernized areas. However, this was no longer statistically significant after adjustment for age and BMI. Lifestyle incongruity was positively associated with higher blood pressure in that those with more discord between material wealth and income were more likely to be hypertensive, and this remained statistically significant after adjustment for age and adiposity. In summary, hypertension is highly prevalent on Saba and tended to be associated with greater age, adiposity, Afro-Caribbean ancestry, and lifestyle incongruity.

The influence of basal metabolic rate on blood pressure among indigenous Siberians

Hypertension is an important global health issue and is currently increasing at a rapid pace in most industrializing nations. Although a number of risk factors have been linked with the development of hypertension, including obesity, high dietary sodium, and chronic psychosocial stress, these factors cannot fully explain the variation in blood pressure and hypertension rates that occurs within and between populations. The present study uses data collected on adults from three indigenous Siberian populations (Evenki, Buryat, and Yakut [Sakha]) to test the hypothesis of Luke et al. (Hypertension 43 (2004) 555-560) that basal metabolic rate (BMR) and blood pressure are positively associated independent of body size. When adjusted for body size and composition, as well as potentially confounding variables such as age, smoking status, ethnicity, and degree of urbanization, BMR was positively correlated with systolic blood pressure (SBP; P < 0.01) and pulse pressure (PP; P < 0.01); BMR showed a trend with diastolic blood pressure (DBP; P = 0.08). Thus, higher BMR is associated with higher SBP and PP; this is opposite the well-documented inverse relationship between physical activity and blood pressure. If the influence of BMR on blood pressure is confirmed, the systematically elevated BMRs of indigenous Siberians may help explain the relatively high blood pressures and hypertension rates documented among native Siberians in the post-Soviet period. These findings underscore the importance of considering the influence of biological adaptation to regional environmental conditions in structuring health changes associated with economic development and lifestyle change.

Culture and the socialization of child cardiovascular regulation at school entry in the US

The measurement of cardiovascular functioning targets an important bridge between social conditions and differential well-being. Nevertheless, the biocultural, psychosocial processes that link human ecology to cardiovascular function in children remain inadequately characterized. Childrearing practices shaped by parents' cultural beliefs should moderate children's affective responses to daily experience, and hence their psychophysiology. The present study concerns interactions among family ecology, the normative social challenge of entry into kindergarten, and parasympathetic (vagal) cardiac regulation in US middle-class children (N = 30). Although parents believed children must be protected from overscheduling to reduce stress and improve socio-emotional adaptation, maternal rather than child schedules predicted parasympathetic regulation during a nonthreatening social engagement task following school entry. Children of busier married mothers, but less busy single mothers, showed the context-appropriate pattern of parasympathetic regulation, low respiratory sinus arrhythmia (RSA). These findings are expected if: maternal and family functioning, rather than the scheduling of the child's daily life, principally drive young children's cardiovascular responsiveness to a normative challenge; and busy schedules represent high family functioning with married mothers, but not under single-parent conditions wherein adult staffing is uniquely constrained. Family ecology is shaped by culture, and in turn shapes the development of children's cardiovascular responses. Appropriately fine-grained analysis of daily experience can illustrate how culturally driven parenting practices may have unintended consequences for child biological outcomes that vary by family structure.

Incorporating psychosocial health into biocultural models: preliminary findings from Turkana women of Kenya

This paper investigates the potential benefits and limitations of including psychosocial stress data in a biocultural framework of human adaptability. Building on arguments within human biology on the importance of political economic perspectives for examining patterns of biological variation, this paper suggests that psychosocial perspectives may further refine our understanding of the mechanisms through which social distress yields differences in health and well-being. To assess a model that integrates psychosocial experiences, we conducted a preliminary study among nomadic pastoralist women from northern Kenya. We interviewed 45 women about current and past stressful experiences, and collected anthropometric data and salivary cortisol measures. Focus group and key informant interviews were conducted to refine our understanding of how the Turkana discuss and experience distress. The results suggest that the most sensitive indicators of Turkana women's psychosocial experiences were the culturally defined idioms of distress, which showed high concordance with measures of first-day salivary cortisol. Other differences in stress reactivity were associated with the frequent movement of encampments, major herd losses, and direct experiences of livestock raiding. Despite the preliminary nature of these data, we believe that the results offer important lessons and insights into the longer-term process of incorporating psychosocial models into human adaptability studies.

Adaptive dimensions of health research among indigenous Siberians

Present evidence suggests that modern humans were the first hominid species to successfully colonize high-latitude environments (> or =55 degrees N). Given evidence for a recent (<200,000 years) lower latitude naissance of modern humans, the global dispersal and successful settlement of arctic and subarctic regions represent an unprecedented adaptive shift. This adaptive shift, which included cultural, behavioral, and biological dimensions, allowed human populations to cope with the myriad environmental stressors encountered in circumpolar regions. Although unique morphological and physiological adaptations among contemporary northern residents have been recognized for decades, human biologists are only now beginning to consider whether biological adaptations to regional environmental conditions influence health changes associated with economic modernization and lifestyle change. Recent studies have documented basal metabolic rates (BMRs) among indigenous Siberian populations that are systematically elevated compared to lower latitude groups; this metabolic elevation apparently is a physiological adaptation to cold stress experienced in the circumpolar environment. Important health implications of metabolic adaptation are suggested by research with the Yakut (Sakha), Evenki, and Buriat of Siberia. BMR is significantly positively correlated with blood pressure, independently of body size, body composition, and various potentially confounding variables (e.g., age and smoking). Further, this research has documented a significant negative association between BMR and LDL cholesterol, which remains after controlling for potential confounders; this suggests that high metabolic turnover among indigenous Siberians has a protective effect with regard to plasma lipid levels. These results underscore the importance of incorporating an evolutionary approach into health research among northern populations.

Aging in Amazonia: blood pressure and culture change among the Cofán of Ecuador

There has been an increasing interest by researchers to study aging among various "traditional societies." However, few studies have specifically examined the differences between lifestyle variables and cardiovascular risk factors among sex-specific age cohorts in Amazon populations. In Western societies, age, obesity, fat distribution, and diet are common correlates of blood pressure (BP). However, these variables may not be significant correlates of BP in more traditional-living societies. For example, outside pressures placed upon their environments and lifestyles can ultimately affect their overall health status. Currently, there are few isolated Amazonian groups pursuing even modified versions of their traditional lifeways. Those that do exist have been reduced by numerous factors, including land conflicts, pollution, infectious diseases, and persistent pressures to acculturate into the dominant society. In most traditional living groups, older individuals appear to be the most resistant to social change. However, the definition of 'older' in these populations is a group-specific cultural construct. This study examines intravillage and intervillage sex-specific cohorts to investigate the complex relationships between age, cultural change and cardiovascular risk factors among an Amazonian population, the Cofán of Northeastern Ecuador.

Anger expression and lifestyle incongruity interactions on blood pressure in Samoan adults

Prior research on psychosocial stress and blood pressure (BP) in adult Samoans identified the separate influences of lifestyle incongruity and anger expression within the context of societal modernization. The objective of this cross-sectional study was to determine the interactions between lifestyle incongruity and anger expression on BP in 376 men and women 25-65 years of age from Samoa. Participants were randomly selected from nine villages. Body mass index (BMI) and BP were measured by standard techniques. Anger expression was measured with an adapted version of the Spielberger Inventory. Material lifestyle was assessed by inventory of household items, exposure to news media, and off-island travel. Occupation and education lifestyle incongruities were calculated by subtracting the standardized lifestyle scale from the standardized occupation and education scales, respectively. Two-factor analysis of variance models with interactions were estimated within specific subgroups, with age- and BMI-adjusted BP as outcomes. In women <40 years of age with a material lifestyle relatively lower than their educational rank, anger suppression is associated with higher adjusted systolic BP. In young men whose material lifestyle is relatively lower than their occupational rank, those who report frequent experiences of Samoan culture-specific anger feelings have higher adjusted diastolic BP. We hypothesize that among young women, the higher BP may be due to stress arising from both a normative proscription against emotional expression, and a mismatch between their relatively higher educational level and lower material lifestyle. For young men, higher BP levels may be attributed to expected donations of earnings to the extended family that exceed their own material lifestyle, in combination with more frequent Samoan-specific feelings of anger.

The Detrimental Effects of Allostasis: Allostatic Load as a Measure of Cumulative Stress

Since its inception in the 1980s, through further developments during the 1990s, and continuing today, the paradigm of allostatic load (AL) has becomed an important paradigm for predicting senescence and mortality. AL is a cumulative measure of the effects of multiple stressors and the process of responding to stressors on the soma. AL measurements of individuals is being tested on various samples and species and being reported across a variety of medical and social science journals. From the ISI Web of Science, all articles published between January 2000 and June 2005 with AL in any default category were obtained and transferred to Endnote. These articles, categorized as theory/review or data-driven, human or animal, and variability in risk factors used to estimate AL, are reviewed here. Only two of 90 reports were published in anthropological journals, likely, at least partly, because research on AL has focused more on western, industrialized populations where data are more easily obtained. From 2000-2005, 12 of 42 data-driven reports focused on elderly humans. Studies of animal models also are common (0 in 2000, but 4 in 2004 covering 21 species). During the last year, multiple additional potential physiological variables have been tested as measures of AL (10 to 20 in any one article). In the past half decade, AL also has been introduced to a wide range of disciplines, including psychology, anthropology, gerontology, veterinary medicine, and medical specialties, as a viable research theme. AL appears to provide a useful method for determining cumulative somatic stress such as that seen with senescence and frailty at older ages.

Cultural consonance and arterial blood pressure in urban Brazil

In previous research in Brazil, we tested the hypothesis that cultural consonance is associated with arterial blood pressure. Cultural consonance is the degree to which individuals are able to approximate in their own behaviors the prototypes for behavior encoded in shared cultural models. Individuals who had higher cultural consonance in the domains of lifestyle and social support had lower blood pressures. The aim of the current research was to replicate and extend these findings. First, a more extensive cultural domain analysis was carried out, improving the description of cultural models. Second, more sensitive measures of cultural consonance were developed. Third, data were collected in the same community studied previously. The following findings emerged: (a) cultural domain analysis (using a mix of quantitative and qualitative techniques) indicated that cultural models for these domains are widely shared within the community; (b) the associations of cultural consonance in these domains with arterial blood pressure were replicated; and, (c) the pattern of the associations differed slightly from that observed in earlier research. This pattern of associations can be understood in terms of macrosocial influences over the past ten years. The results support the importance of long-term fieldwork in anthropology.

Changes in financial strain over three years, ambulatory blood pressure, and cortisol responses to awakening

OBJECTIVE

Chronic psychosocial stress has been associated cross-sectionally with ambulatory blood pressure and with salivary cortisol, but there have been few longitudinal studies of the effects of changes in chronic stress. We assessed the influence of changes in financial strain on ambulatory blood pressure and salivary cortisol.

METHODS

Data were analyzed from 160 men and women age 47 to 59 years at the first assessment (T1) who repeated ambulatory monitoring 3 years later (T2). We analyzed change in financial strain as a continuous variable, and specifically compared people who did and did not report an improvement in financial strain.

RESULTS

Change in financial strain was associated with change in ambulatory systolic pressure after controlling for T1 ambulatory systolic pressure, gender, socioeconomic position, age, smoking, body mass index, and T1 financial strain (p = .041). Systolic pressure at T2 was lower in the improved financial strain (121.7 +/- 11.2 mm Hg) than in the worse/no change group (125.5 +/- 11.5 mm Hg; p = .029). The corresponding diastolic pressures averaged 78.5 +/- 7.1 mm Hg and 80.7 +/- 7.9 mm Hg, respectively (p = .061). The cortisol awakening response (difference between waking and 30 minutes later) was lower (p = .048) in men who reported improved financial strain, controlling for T1 cortisol response, socioeconomic position, age, smoking, time of waking, and T1 financial strain. There were no differences in the slope of cortisol decline over the day or in evening values.

CONCLUSION

These longitudinal data extend cross-sectional findings in showing associations between favorable changes in chronic stress and reduced cardiovascular and neuroendocrine activation in everyday life.

Blood pressure, seasonal body fat, heart rate, and ecological differences in Caboclo populations of the Brazilian Amazon

This study compares blood pressure (BP) and related cardiovascular risk factors among three Caboclo communities from the Brazilian Amazon. Its purpose is to investigate possible risk differentials related to variable ecological settings and Western influences. Caxiuanã is characterized as a more "traditional" group, while Aracampina and Santana are viewed as more "transitional" in lifestyle. A total of 348 subjects from the three communities were evaluated in the wet or the dry season or in both. Measurements across the communities were compared by season and sex. Results suggest little seasonal variation in average BP, BP change, body fat, or body fat change among men. Conversely, there is substantial seasonal and inter-community variation among women. Additional analyses reveal (1) an inconsistent association between age and BP across the communities; (2) that BMI is not associated with BP transitional communities in either season but is associated with both systolic and diastolic pressure in the most traditional community; and (3) little to no sex effect on BP. These results suggest increased Western influence affects body composition particularly of women. However, increased BMI and fat among transitional Caboclo women does not directly translate into higher BP; rather, their BP appears to be more affected by seasonal stresses. Finally, conditions during the wet season diminish age-related variation in BP, suggesting that during the wet season these Caboclo may be less active.

Basal metabolic rate in the Yakut (Sakha) of Siberia

Human indigenous circumpolar populations have elevated basal metabolic rates (BMRs) relative to predicted values; this metabolic elevation has been postulated to be a physiological adaptation to chronic and severe cold stress. The present study examines BMR in the Yakut, an indigenous high-latitude population from the Sakha Republic of Russia to determine (1) whether the Yakut show evidence of an elevated BMR, (2) if the Yakut display evidence of age-related changes in BMR, and (3) whether lifestyle differences influence BMR. BMR was measured during the late summer in 75 women and 50 men (ages 18-56 years) from the Siberian village of Berdygestiakh. Measured BMR (+/- SEM) of the entire sample was significantly elevated (+6.5%) compared to predictions based on body mass (6,623.7 +/- 94.9 vs. 6,218.2 +/- 84.7 kJ/day; P < 0.001). Additionally, measured BMR for the entire sample was significantly higher than predictions based on fat-free mass (+20.8%) and surface area (+8.9%). Males and females both showed significant elevations relative to all three standards. The elevated BMR of the Yakut does not appear to be attributable to extreme levels of protein, since the Yakut consume a mixed diet with a substantial proportion of carbohydrates. No significant age-related changes in BMR were found when controlled for body composition. No significant relationship was found between lifestyle variables and BMR, suggesting the possibility of a genetic or developmental mechanism. This study provides additional evidence of metabolic elevation in indigenous circumpolar groups and has important implications for estimating the nutritional requirements of these populations.

Population genetics of apolipoproteins A-IV, E, and H, and the angiotensin converting enzyme (ACE): associations with lipids, and apolipoprotein levels in American Samoans

Distributions of alleles at three apolipoprotein loci (APO E, APO H, and APO A-IV) and an insertion/deletion (I/D) polymorphism at the angiotensin converting enzyme (ACE) locus among 274 American Samoans are described here. Genotypes at each locus are examined for associations with quantitative lipid (total cholesterol (total-c), LDL-cholesterol (LDL-c), HDL-cholesterol (HDL-c), and triglycerides) and apolipoprotein (APO AI, APO AII, APO E, and APO B) levels. Genotype frequencies at all four loci are in Hardy-Weinberg equilibrium. The most common APO A-IV genotype (1-1) was observed in 252 American Samoans (97%). The three most common APO E genotypes were 3-3 (47%), 3-4 (30%), and 2-3 (12%). The most frequent APO H genotype was 2-2 (86%). The most common ACE genotype (I/I) was observed in 75% of sampled individuals, and 23% were I/D heterozygotes. APO E genotypic variation was associated with total-c, HDL-c, LDL-c, and all four quantitative apolipoproteins (AI, AII, E, and B). APO A-IV genotypes were associated significantly with total cholesterol, LDL-c, and APO-B levels. APO H showed little association with any quantitative lipid or apolipoprotein. ACE D/D homozygotes had higher AII levels. ACE showed a consistent association with APO AII levels, with either APO A-IV or APO E as a covariate. The interaction term between ACE and APO E was also significantly associated with total-c and APO E levels, and the ACE genotype showed a significant main effect on APO AI levels in multivariate analyses.

Status incongruity in Samoan youth: a biocultural analysis of culture change, stress, and immune function

In Samoa, the presence of a matai title in the family has historically been a valued source of social status. However, as the process of Westernization continues, new sources of social status are emerging. This study explores the degree to which new and old markers of social status agree--or disagree--and the consequences they have for the experience of stress in 329 Samoan adolescents. The study integrates cultural and biological methods and data, and measures an aspect of immune function (antibodies against the Epstein-Barr virus) as a biomarker of psychosocial stress. Results indicate that status "incongruent" adolescents experience significantly more stress (indicated by reduced immune function), and that emerging markers of social status are becoming inextricably linked to "traditional" markers in such a way that discordance between them is a significant source of stress. This study proposes new conceptual models for future studies of culture change and suggests that biomarkers may represent ethnographic tools that can provide insight into hidden cultural dynamics and the experience of stress.

Household economic strategies and nutritional anthropometry of women in American Samoa and highland Bolivia

This study compares findings from research projects involving different genetic, environmental, and cultural contexts: a study of lifestyle and health from American Samoa (ASLS) and the Bolivian project. Reproduction and Ecology in Provincia Aroma (REPA). This paper presents analyses of varying economic strategies and their association with nutritional status indicators in each population. The ASLS sample includes 66 Samoan women and the REPA sample includes 210 Aymara women. Principle components analysis of household economic resources within each sample extracted two significant factors: one represents modernizing influences including education and occupational status, and the other represents ethnographically salient traditional economic behavior. The traditional pattern includes adding household members in Samoa and selling agricultural products in Bolivia. This analysis places each woman along two continua, traditional and modern, based on her household mobilization of economic resources, permitting an understanding of the patterns underlying household economic behavior that is not possible in univariate analyses of socioeconomic variables. For the Bolivian women the strategy involving more education and higher occupational status was associated with higher measures of several nutritional status indicators, including body mass index, arm muscle area, and peripheral skinfolds. But among the Samoan women, where substantial obesity was the norm, there were no significant differences in anthropometric measurements based on economic strategies. These data argue for the importance of directly measuring the potential consequences of variation in household economic strategies rather than merely inferring such, and of assessing ethnographically relevant aspects of household economic production rather than limiting analyses to non-context-specific economic indicators such as income. This focus on household strategy is likely to be fruitful especially where economic and nutritional conditions are marginal. The findings from Bolivia also support efforts in developing countries to improve girls' education, and thereby occupational prospects, as a means to improve their health status as women.

Lifestyle incongruity, social integration, and immune function in Samoan adolescents

The health consequences of rapid cultural and economic change have been explored for adults in a range of low-income countries, but comparable research in children and adolescents is currently lacking. Concurrently, the immunosuppressive effects of psychosocial stress have been documented in Western populations, but have yet to be considered in cross-cultural contexts. This study uses lifestyle incongruity (inconsistency between a household's material style of life and its socioeconomic status) as a model of culture change and stress, and considers its impact on immune function in a sample of 230 10-20 year-olds from (Western) Samoa. Anthropometric, lifestyle, and psychosocial data were collected, as well as finger prick blood spot samples for analysis of C-reactive protein (marker of infection) and antibodies against the Epstein-Barr virus (marker of cell-mediated immune function). Controlling for potential confounders, adolescents from households with a material style of life that exceeds its socioeconomic status have reduced cell-mediated immune function, indicating an increased burden of psychosocial stress. Social relationships moderate this effect: lifestyle incongruity stress is pronounced among adolescents with a high degree of social integration, and absent in adolescents with low social integration. This finding is counter to the buffering role of social support reported in previous applications of lifestyle incongruity to adults, and suggests that the moderating role of social integration may be unique to adolescents. The potential utility of the lifestyle incongruity model for future cross-cultural studies of child and adolescent stress is discussed.

Culture change and stress in Western Samoan youth: Methodological issues in the cross-cultural study of stress and immune function

This study was designed to pursue three objectives: 1) investigate the impact of culture change on children and adolescents in Western Samoa; 2) introduce a cross-cultural perspective to studies of psychosocial stress and immune function; and 3) evaluate the utility of minimally invasive methods for assessing immune function. Seven hundred sixty individuals between the ages of 4 and 20 years were recruited from three distinct geographic regions within Western Samoa that differ in degree of westernization. Finger prick samples of whole blood were collected from each individual and analyzed for antibodies against the Epstein-Barr virus (EBV; an indirect marker of cell-mediated immune function) and C-reactive protein (a nonspecific marker of current infection). After controlling for age, sex, and current infection, EBV antibody levels were significantly elevated in urban Apia and rural Upolu, indicating lower levels of cell-mediated immune function. The results suggest a higher degree of psychosocial stress in these regions, possibly due to exposure to westernizing influences. Am. J. Hum. Biol. 12:792-802, 2000. Copyright 2000 Wiley-Liss, Inc.

Sociocultural change and health status among the Seri Indians of Sonora, Mexico

The influence of changes in sociocultural status on obesity, arterial blood pressure, and depression was examined in a cohort of 81 Seri Indians living in two communities in Sonora, Mexico. Residents of the less acculturated and modernized community, Desemboque, exhibited significantly higher waist circumference and prevalence of obesity than did residents of the more acculturated and modernized community of Punta Chueca. The prevalence of obesity was also significantly associated with low levels of acculturation and modernization, while the prevalence of clinically significant depressive symptoms was associated with low levels of modernization and household income. Lifestyle incongruity was a significant independent risk factor for body mass index and depressive symptom scores but not for arterial blood pressure. The results support the notion of a curvilinear relationship between health status and sociocultural change in which health status initially declines with increasing lifestyle incongruity but eventually improves with increasing acculturation, modernization, and income.