Sabrina C. Agarwal

Bone Quantity and Quality in Past Populations

The study of osteoporosis in past populations offers valuable insight into the patterns and prevalence of the disease in both the past and in the present.

Techniques for the Investigation of Age-Related Bone Loss and Osteoporosis in Archaeological Bone

With increasing awareness of age-related bone loss and osteoporosis in modern Western populations, a growing number of studies have set out to investigate whether individuals in the past were similarly affected (Martin and Armelagos, 1979; Bennike and Bohr, 1990; Lees et al., 1993; Agarwal and Grynpas, 1996; Brickley and Howell, 1999; Drusini et al., 2000; Mays, 2000). Research has demonstrated that age-related bone loss and osteoporosis results in changes to cortical bone (Derisquebourg et al., 1994), structural changes to trabecular bone (at a gross and microscopic level [Jayasinghe, 1994]), and bone mass and density (Cummings et al., 1993). Bone turnover and age-related bone loss are highly complex processes (see Chapters 1 and 2, this volume). The interaction between bone loss in both cortical and trabecular bone throughout the skeleton allows a variety of possible approaches to the study of bone loss. A range of techniques have been developed, each of which allows assessment of a different aspect of bone loss. Although this area has generated a great deal of recent interest, the epidemiology of age-related bone loss and fragility fractures, both in clinical and archaeological contexts, is unclear. The history of the development of the disease is not yet fully understood and a range of possibilities is currently being explored. For example, (1994) suggest that increasing bone loss may be an evolutionary trend (see also Chapter 8, this volume).

Bone morphologies and histories: Life course approaches in bioarchaeology.

The duality of the skeleton as both a biological and cultural entity has formed the theoretical basis of bioarchaeology. In recent years bioarchaeological studies have stretched the early biocultural concept with the adoption of life course approaches in their study design and analyses, making a significant contribution to how we think about the role of postnatal plasticity. Life course theory is a conceptual framework used in several scientific fields of biology and the social sciences. Studies that emphasize life course approaches in the examination of bone morphology in the past are united in their interrogation of human life as a result of interrelated and cumulative events over not only the timeframe of individuals, but also over generations at the community level. This article provides an overview of the theoretical constructs that utilize the life course concept, and a discussion of the different ways these theories have been applied to thinking about trajectories of bone morphology in the past, specifically highlighting key recent studies that have used life course approaches to understand the influence of growth, stress, diet, activity, and aging on the skeleton. The goal of this article is to demonstrate the scope of contemporary bioarchaeological studies that illuminate the importance of environmental and behavioral influence on bone morphology. Understanding how trajectories of bone growth and morphology can be altered and shaped over the life course is critical not only for bioarchaeologists, but also researchers studying bone morphology in living nonhuman primates and fossil primate skeletons.

Measuring and interpreting age-related loss of vertebral bone mineral density in a medieval population.

This study investigates the age- and sex-related patterns in vertebral bone mineral density (BMD) and the relationship between BMD and vertebral osteophytosis (VO), using a specialized peripheral densitometer in a skeletal sample excavated from the British medieval village Wharram Percy. A total of 58 individuals were divided by sex into three broad age categories (18-29, 30-49, 50+ years.). Each fourth intact vertebral centra was scored for VO and 5-mm thick coronal sections scanned in a specialized peripheral densitometer (GE Lunar Piximus DXA). Changes in BMD associated with age, sex, and VO severity were examined in the whole vertebral section, a strictly trabecular region, and a primarily cortical region of bone separately. Significant change in vertebral BMD was found to occur by middle age with little or no statistical change in BMD between middle and old age. Females appear to suffer greater bone loss at an earlier age with no change in BMD between middle and old age, whereas males show a more steady loss of BMD across the age groups. The bone mineral content and BMD of the cortical region is higher in individuals with pronounced/severe osteophytosis. The unusual age- and sex-related patterns of change in vertebral BMD at Wharram Percy are compared with the patterns of age-related change from recent longitudinal population-based studies. The results emphasize the different pattern of bone loss in young adulthood seen in trabecular regions of the skeleton and highlight the importance of consideration of degenerative joint disease in BMD studies. The influence of lifestyle factors on vertebral BMD in this medieval population is also discussed.

An Evolutionary and Biocultural Approach to Understanding the Effects of Reproductive Factors on the Female Skeleton

Osteoporosis is a systemic skeletal disease characterized by a reduction in bone mass and a deterioration of the microstructure of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture. The precise mechanisms and etiology of the disease are incompletely understood. Age-related bone loss is found in both sexes, but is accelerated in females with the onset of menopause. Bone loss in postmenopausal years averages anywhere between 1–5% per year, increasing the risk of a 50-year old white woman sustaining a fracture at any skeletal site to 30–40% (Melton, 1995). Further, secular trends in Europe and North America indicate that the incidence of fragility fracture has doubled over the last three decades, creating a serious social and financial burden (Melton, 1995).

Evolutionary aspects of bone health

The period during which our human ancestors evolved is miniscule in relation to the evolutionary record of all living things. However, the speed with which the human species changed is unique among animals. This article reviews basic evolutionary forces as well as the timeline from the first appearance of early hominids through the modern age. The distinctive feature of human evolution is the combination of biology and culture that characterizes human adaptation. Presumably, the need for specific skeletal characteristics (e.g., size, shape, density) changed as early hominids experienced major shifts in adaptation. These shifts include expansion from the tropics to a wide range of environments; transition from hunting and gathering to food production; change from physically active lifestyles to relative sedentism; and increase in life expectancy. These changes can be related in some ways to the modern problem of osteoporosis. An understanding of mans evolutionary past holds important lessons and provides insight into safeguarding this aspect of health as man moves into the new millennium.

Hydroxylapatite lattice preferred orientation in bone: a study of macaque, human and bovine samples

Hydroxylpatite crystallites in lamellar bone show preferred orientation. In this study, the texture (lattice preferred orientation) of the crystallites in cortical bone samples has been studied by means of synchrotron hard X-ray diffraction, performing a combined analysis with the Rietveld method to quantify fully the preferred orientation features and to obtain lattice and microstructural parameters (such as crystallite size) simultaneously. The samples were ribs from four adult female macaques of different ages, and two femurs chosen for comparison, one from a human child and one from an adult cow. The effect of the preferred orientation of the mineral component on the elastic properties is also briefly discussed. All six samples, averaging volumes of ∼0.5 mm3, show strong preferred orientation, with the hydroxylapatite c axis parallel to the bone axis. The symmetry of the texture is almost perfectly axial and clearly displays a uniform girdle of the a axis perpendicular to the bone axis. The texture strength is very similar for the four macaque rib samples, while some variation is observed in the human (weaker) and bovine (stronger) femurs. The crystallite size (8 × 30 nm) and unit-cell lattice parameters are similar in all samples. The Rietveld analysis provides for the first time a quantitative texture analysis combined with structural and microstructural hydroxylapatite analysis of the same bone samples.

Evolutionary aspects of bone health: development in early human populations.

The period during which our human ancestors evolved is miniscule in relation to the evolutionary record of all living things. However, the speed with which the human species changed is unique among animals. This article reviews basic evolutionary forces as well as the timeline from the first appearance of early hominids through the modern age. The distinctive feature of human evolution is the combination of biology and culture that characterizes human adaptation. Presumably, the need for specific skeletal characteristics (e.g., size, shape, density) changed as early hominids experienced major shifts in adaptation. These shifts include expansion from the tropics to a wide range of environments; transition from hunting and gathering to food production; change from physically active lifestyles to relative sedentism; and increase in life expectancy. These changes can be related in some ways to the modern problem of osteoporosis. An understanding of mans evolutionary past holds important lessons and provides insight into safeguarding this aspect of health as man moves into the new millennium.

A multi-method assessment of bone maintenance and loss in an Imperial Roman population: Implications for future studies of age-related bone loss in the past

OBJECTIVES One of the hallmarks of contemporary osteoporosis and bone loss is dramatically higher prevalence of loss and fragility in females post-menopause. In contrast, bioarchaeological studies of bone loss have found a greater diversity of age- and sex-related patterns of bone loss in past populations. We argue that the differing findings may relate to the fact that most studies use only a single methodology to quantify bone loss and do not account for the heterogeneity and complexity of bone maintenance across the skeleton and over the life course. METHODS We test the hypothesis that bone mass and maintenance in trabecular bone sites versus cortical bone sites will show differing patterns of age-related bone loss, with cortical bone sites showing sex difference in bone loss that are similar to contemporary Western populations, and trabecular bone loss at earlier ages. We investigated this hypothesis in the Imperial Roman population of Velia using three methods: radiogrammetry of the second metacarpal (N = 71), bone histology of ribs (N = 70), and computerized tomography of trabecular bone architecture (N = 47). All three methods were used to explore sex and age differences in patterns of bone loss. RESULTS The suite of methods utilized reveal differences in the timing of bone loss with age, but all methods found no statistically significant differences in age-related bone loss. DISCUSSION We argue that a multi-method approach reduces the influence of confounding factors by building a reconstruction of bone turnover over the life cycle that a limited single-method project cannot provide. The implications of using multiple methods beyond studies of bone loss are also discussed.

Bone Health from an Evolutionary Perspective: Development in Early Human Populations

Skeletal characteristics, bone health, and the risk of osteoporosis differ within and between modern day populations, and almost certainly reflect our evolutionary past. In this chapter, we review the major evolutionary events among the hominins, the human sub-family of primates, and provide an overview of evolutionary mechanisms resulting in the genetic changes that helped our ancestors to adapt to diverse environments. The skeleton can also be affected by a number of environmental and cultural factors, including diet, physical activity, work patterns, health and disease. For the purposes of examining evolutionary aspects of bone health, it is fortunate that bones can be preserved in the fossil record, and certain artifacts of cultural adaptation may also be present in hominin fossil sites. Anthropological techniques have been developed that allow us to create reasonable models of life in past human populations, thereby providing some insight into modern-day bone health. The major biocultural shifts during hominin evolution include the following: expansion from the tropics to a wide range of environments; transition from hunting and gathering to food production; change from physically active lifestyles to relative sedentism; and increase in life expectancy, with changes in reproductive behaviors. These four areas form the focal points for an examination of human bone health from an evolutionary perspective.