Ageing and physical function in East African foragers and pastoralists.

Human lifespans are exceptionally long compared with those of other primates. A key element in exploring the evolution of human longevity is understanding how modern humans grow older. Our current understanding of common age-related changes in human health and function stems mostly from studies in industrialized societies, where older adulthood is often associated with an increased incidence of chronic diseases. However, individuals who engage in different lifestyles across industrialized and non-industrialized contexts may display variance in age-related changes in health and function. Here, we explore aspects of physical function in a non-industrialized context using three objective measures of physical function. We assessed physical activity levels, walking endurance and muscle strength in two East African populations: Hadza hunter-gatherers in Tanzania and Pokot pastoralists in Kenya. Both Hadza and Pokot participants displayed significant age-related differences in most, but not all, functional measures. Our results suggest that some age-related differences in physical function seen in industrialized contexts could be consistently experienced by most humans, while other age-related differences may vary across populations. Studies of ageing should expand to include a broad range of populations so we can create a more comprehensive understanding of how senescence varies across different lifestyle contexts. This article is part of the theme issue 'Evolution of the primate ageing process'.

"My own corner of loneliness:" Social isolation and place among Mexican immigrants in Arizona and Turkana pastoralists of Kenya.

This article explores the intersection of two growing health concerns: the rising incidence of loneliness and the negative health impacts of migration and displacement. To better evaluate loneliness across diverse populations, we emphasize the cultural shaping of expectations for social lives and the ways in which structural vulnerability and violence can undermine these expectations. We draw on ethnographic research with two groups of migrants: Mexican immigrants living in southern Arizona and Turkana pastoralists of Kenya who experience displacement and unpredictable mobility as a result of low intensity violence. For Mexican immigrants, feelings of loneliness intertwine with the emotions of fear, trauma, and sadness, all closely associated with social isolation. The Turkana describe loneliness associated with the loss of their animals, or the shifting social landscapes they must traverse to keep their families safe. The culturally salient experiences described by these two communities highlight the complexity of defining loneliness. Given the pace of global migration and the number of refugees and displaced persons, closer scrutiny of how cultural expectations and structural violence interact to produce feelings of loneliness seems overdue.

High levels of objectively measured physical activity across adolescence and adulthood among the Pokot pastoralists of Kenya.

OBJECTIVES: Levels of physical activity (PA) across the lifespan are important predictors of physical fitness, impacting individual health, and longevity. Individuals living in industrialized societies are often characterized as more sedentary than those who live in small-scale societies, and this inactivity is generally linked with increased incidence of chronic disease, especially during aging. However, less empirical data exist regarding levels and patterns of PA across the lifespan among small-scale societies compared with industrialized societies. The goal of this study was to characterize PA among the Pokot pastoralists of rural northern Kenya. METHODS: PA was measured in 40 participants ranging in age from 14 to 78 years using ActiGraph wrist-worn accelerometers. Wear time spanned 24-77 hours, with a modal wear time of 50 hours. RESULTS: We show that the Pokot spend large amounts of time in moderate-to-vigorous physical activity (MVPA), achieving an average of 99.14 ± 7.25 minutes per day in MVPA. Males and younger participants tended to spend more time in MVPA. However, older participants were still physically active and engaged in over 50 minutes per day of MVPA. CONCLUSIONS: The Pokot are highly physically active from adolescence through adulthood. Other pastoralist groups may display a similar pattern of PA. During human evolution, lifespans increased, and lifestyles were characterized by a relatively high level of physical activity. The human aging process may be adapted for activity throughout life, and lifelong activity may have played an important role in increases in human longevity during evolution.

Low-intensity violence and the social determinants of adolescent health among three East African pastoralist communities.

Recently, strong pleas have emerged to place the health of adolescents on the global health agenda. To reposition adolescence front and center, scholars argue that we must work toward a richly contextualized approach that considers the role that social environments play in shaping the final stages of growth and development. We aim to contribute to this deeper understanding of the social determinants of global adolescent health by offering a case study of three nomadic pastoralist communities from northern Kenya. In addition to noteworthy political and economic marginalization, East African pastoralist communities also contend with chronic, low intensity intercommunity conflict. Data collected over five extensive visits from 2008 to 2011, include the 10-19 year olds from 215 randomly sampled Pokot, Samburu, and Turkana households. Using a case/control design, we sampled two sites per ethnic community: one directly affected and one less affected by intercommunity violence. Our nutritional findings indicate that teens ages 15-19 years old had significantly higher anthropometric values compared to younger teens. Living in a wealthier household is associated with greater height, body mass indices, and summed skinfolds for boys but not for girls. Anthropometric measures were influenced by household and community variation in the mixed-effects, multi-level regression models. The Self-Report Questionnaire (SRQ-20) was used to assess psychosocial health, with higher scores associated with living in a community directly affected by violence and having lost a loved one due to violence. Our findings highlight the unique nature of adolescent health challenges but also the central role even subtle differences across communities and households play in shaping young people's experiences. With few studies to document the lived experience of pastoralist youth as they move toward adulthood, examining how such challenging socioeconomic environment shapes health seems long overdue.

A biocultural framework for examining maternal cravings and aversions among pastoral women in east Africa.

Food preferences during pregnancy result from a complex set of biocultural interactions with important implications for maternal and child health. This article explores the social context of maternal food choice in marginal environments of East Africa. Biocultural data collected among Turkana and Datoga women living in Kenya and Tanzania indicate there is a significant social context to food choice that influences the types of food that women report craving and the food that is consumed. Our framework argues for a deeper understanding of how culture shapes food preferences and how marginalization can constrain access to favored and healthy foods.

Documenting the health consequences of endemic warfare in three pastoralist communities of northern Kenya: a conceptual framework.

Violent conflict represents the third most important source of mortality around the world, yet violence-related mortality remains profoundly undercounted (Krug, Dahlberg, Mercy, Zwi, & Lozano, 2002). As a step toward documenting the consequences of even the "smallest wars" we offer a conceptual framework for a recently initiated project that comparatively examines the direct and indirect consequences of intercommunity violence among Pokot, Samburu, and Turkana herding communities of Northern Kenya. While a substantial body of work has accumulated on the social responses to this violence very little is known about the differential impacts on community health. Based on our cumulative ethnographic experience in the area, we offer a conceptual framework that merges a context-sensitive ethnographic approach with a comparative epidemiological one centered on documenting the lived experience of violence and inequality. In this paper, we provide evidence for the importance of a contextualized approach detailing how social environments that include chronic episodes of violence produce variations in health. We do so by presenting the results of previous work to highlight what is known and follow this by identifying what remains to be understood about how violence, inequality, and health interact in these communities. While much is known about the importance of access to livestock herds for health, nutrition, and child growth in this difficult physical environment, far less is known about how the social responses to violence interact with access to herds to create new patterns of nutrition and health. With respect to pastoralists, additional areas that remain only nominally understood include age-specific mortality patterns, reproductive health, and psychosocial/mental health, topics that we view as central to the current study. In sum, we suggest that health offers one of the most useful tools for examining the costs of violence by creating opportunities for advocacy.

Understanding women's burdens: preliminary findings on psychosocial health among Datoga and Iraqw women of northern Tanzania.

This preliminary, community-based study examines major stressors identified by Iraqw and Datoga women of Mbulu District, Tanzania, and describes steps in creating a culturally specific questionnaire to assess mental health burdens. This area of Tanzania is remote, with limited access to goods and services, and is undergoing dramatic social and economic changes. Iraqw and Datoga reside in close proximity and often intermarry but have different cultural and subsistence responses to this rapid social change. Data were collected from May to October 2002, with 49 Datoga women and 64 Iraqw women interviewed. In-home interviews were conducted to have women (1) free-list their primary concerns and (2) answer questions from a translated (in Datoga and Iraqw) and modified standardized mental health questionnaire. Both groups of women identified hunger, the lack of animals, particularly cattle, and health/illnesses as the most common major stressors. Other frequently cited stressors included crop failure, general fears of violence, paying taxes, and no money for basic needs. Additional refinements are required for the mental health questionnaire, with strengths and limitations discussed. Such data, while preliminary, augment efforts to analyze the emotional burdens associated with dramatic social change.

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.

Maternal stress and fetal responses: evolutionary perspectives on preterm delivery.

New epidemiological and neurohormonal evidence provides insights into the persistent public health issue of preterm delivery and its long-term health consequences for the newborn. Mechanisms linked to preterm delivery may originate early in gestation as a result of maternal cues signaling a stressful intrauterine environment. When these signals are present, the fetus responds with a series of facultative responses, including accelerated organ maturation. If these responses are unsuccessful and the environment remains insufficient, a series of feed-forward mechanisms initiate the hormonal cascade that leads to parturition, and thus, early expulsion from a stressful environment. The internal environmental cues are delivered via glucocorticoids (stress hormones) in the circulatory system, but fetal responses and the initiation of the final terminal pathway to parturition are regulated by placentally derived corticotropin-releasing hormone (CRH). The potential costs of early expulsion from a stressful intrauterine environment are high and include an increased likelihood of perinatal and infant mortality. Permanent alterations in organ and metabolic functioning may occur, suggesting considerable fitness trade-offs. There is some evidence that preterm parturition is a maternal adaptation to limit the energetic costs of individual pregnancies in the face of poor condition at the time of conception. Moreover, nutritional stress is not the only indicator that signals a stressful environment: maternal psychosocial stress, and thus her response to an assessment of the social environment, also signal an insufficient internal environment to the fetus. The epidemiological and neurohormonal evidence for these relationships and mechanisms responsible for regulating such delicate negotiations are explored. In turn, the implications of such findings are examined from life history and public health perspectives.

Age, reproductive history, seasonality, and maternal body composition during pregnancy for nomadic Turkana of Kenya.

To evaluate the potential differences in maternal nutritional investment in pregnancy, data collected from nomadic Ngisonyoka Turkana women during a July 1993-July 1994 field season were utilized. The roles maternal age, parity, duration of the previous nonpregnant interval, overlap between pregnancy and lactation on trimester changes in weight and summed skinfolds during pregnancy were examined. Because seasonality is an important aspect of the Turkana environment, the effects of seasonality were also assessed. First trimester weight gain is positively associated with overlap in pregnancy and lactation. Second trimester maternal weight gain is negatively influenced by higher parity and by overlap between lactation and early pregnancy. Third trimester weight gain is influenced only by seasonally induced morbidity. First trimester changes in maternal skinfolds are negatively influenced by older maternal age and parity, and positively influenced by a longer nonpregnant interval, and overlap between pregnancy and lactation. Second and third trimester skinfolds are significantly associated only with overlap between lactation and pregnancy (negatively in the second, positively in the third). Seasonality does not influence maternal skinfolds. Differences in age- and parity-related patterns of maternal nutritional investment in pregnancy are not supported by the data. The possibility that Turkana cultural beliefs may influence nutritional status during pregnancy is discussed. Am. J. Hum. Biol. 11:658-672, 1999. Copyright 1999 Wiley-Liss, Inc.