In the introduction to this volume, Ice and James refer to “practical considerations” as an important component when selecting a measure of stress. This chapter will discuss some practical considerations in detail in the consideration of stress measurement in reproductive age women, children, older populations, and in non-clinical settings. Selection of culturally relevant questionnaires and interview techniques in field settings are discussed in detail elsewhere in this volume, so this chapter will focus on the collection of physiological markers of stress in non-clinical settings. Current research has suggested new areas of interest and new biological markers of relevance in these special populations. Some practical considerations discussed in this chapter include selection of relevant and appropriate biological markers of stress in special populations and logistical considerations associated with collecting biological markers in non-clinical settings. Many of these factors can impact compliance rates, the number of individuals who will agree to participate and successfully complete the study as well as the acceptability of biological samples for laboratory analysis.

Stress and reproducing women

Stress and reproductive function

According to the demographer Bongaarts (1983), there are seven “proximate determinants” of fertility that mediate all other variables (e.g. social, economic, and cultural) that control the length of birth intervals. Stress has been suggested to impact reproduction through all of Bongaart's proximate determinants of fertility (Bongaarts, 1983). Consequences of Sympathetic Adrenal Medullary System (SAMS) and/or Hypothalamic Pituitary Adrenal (HPA) axis activation have been identified as interfering with exposure factors (i.e. age at menarche, coital frequency), waiting time to conception (reproductive cycles, ovulation), pregnancy loss, and gestation length (parturition).

All studies involving human subjects must be reviewed and approved by an Internal Review Board (IRB). This board consists of both professional and non-professional (lay) members, and its mission is to reasonably insure that subjects in research are adequately informed about the procedures that they will undergo and that they are protected from harm. In order for successful human stress research to proceed, an investigator needs not only to understand what constitutes ethical research, but also how to convey to the IRB that best practices will be followed in the conduct of the research and that any risks to subjects are minimized. Furthermore, if there are risks to subjects, these must be explained plainly and carefully to the subjects in a consent form prior to their participation, so that the subjects can make an informed decision as to whether or not they want to proceed. Finally, if there are risks, it must be made clear that they are substantially outweighed by the potential benefits to the subject or society. In fact, it is not possible to obtain federal grant money in the USA to study stress or allostatic processes in humans without documenting the protection of human subjects and IRB approval.

Researchers often view the entire process of assembling and submitting human subjects review forms as an onerous and difficult task. Perhaps the single major complaint (or frustration) that is voiced by researchers is that they do not understand what the IRB wants.

Stress implies that a physiological or psychological change has occurred within a subject or that, because of a broader ecological stressor, measurable biological differences between subjects or groups of subjects exist. A variety of study designs can be employed to detect the effects of stress on biology and behavior in the field, although these variants fall under two general categories: 1) natural experiments with an a priori ecological framework and 2) model building or testing where there is no ecological framework per se, but rather a framework of expected relationships based on the results of prior field and/or laboratory research. Depending upon whether a field study of stress is designed to evaluate individual change or group differences, single or multiple measurements per subject can be evaluated.

The purpose of this chapter is to discuss, from a practical standpoint, research design and analytic approaches and techniques that are useful for field studies of stress. The intent is to provide researchers with information on how to develop a meaningful stress study and, hopefully, some insight into how best to evaluate stress-related data. It is not the intent of this chapter to detail specific statistical procedures; however, we will, when necessary, make reference to them.

Research design and the constraints of data collection

In conducting any study of stress response in the field (outside the laboratory), it is best to proceed with a plan in mind, one that will guide not only what data will be collected, but also one that is tied to the analytic technique (statistics) that will be used to test the study hypotheses.

Introduction

Stress is an important determinant of human immune function, but population-level research on the social ecology of immunity has lagged behind other areas of investigation. In large part this is due to methodological constraints associated with the assessment of immune function: venipuncture is a relatively invasive blood sampling procedure that requires the skills of a trained medical professional and, once collected, blood samples must be immediately assayed, or centrifuged, separated, and frozen. Obviously, these are serious impediments to field-based research, and they have hindered the exploration of stress–immunity relationships in large, representative, community-based studies.

Dried blood spots – samples of whole blood collected on filter paper following a simple finger prick – provide an alternative, minimally invasive sampling procedure. Several community-based applications have shown this to be a convenient and reliable means to facilitate sample collection, storage, and transportation, and laboratory methods have been validated for a growing number of analytes (Worthman and Stallings, 1994, 1997; Cook et al., 1998; McDade et al., 2000a; Erhardt et al., 2002; McDade and Shell-Duncan, 2002; McDade et al., 2004). Also referred to as “Guthrie papers,” filter papers have been a core component of US hospital-based newborn screening programs since the 1960s, with all newborns providing a blood spot sample to screen for congenital metabolic disorders (Mei et al., 2001).

In this chapter, detailed information is provided on the collection, handling, and analysis of dried blood-spot samples for two measures of immune activity: Epstein-Barr virus antibodies and C-reactive protein.

Introduction

This chapter aims to review measures of the emotional and behavioral responses to stressors. As reviewed in Chapter 1, there are multiple cognitive responses to a stressor starting with the appraisal of a stressor. After a person appraises a stressor or evaluates it as a threat, s/he will experience a stress response, often including an emotional and behavioral response. For example, an individual is exposed to the stressor of caring for a relative with dementia, s/he may feel burdened, anxious and sad. This same person may engage in various coping behaviors such as smoking or seeking solace at a place of worship. The way that an individual responds to a stressor (from the appraisal through the stress response) depends on various factors (e.g. personality, coping resources) which may mediate or moderate the way in which an individual appraises and then responds to a stressor. For example, this same caregiver, may have a large supportive family which minimizes the appraisal of threat or the emotional response in comparison to an individual without such support. The reader should refer to Chapters 1 and 2 for the definition of the concepts of mediators, moderators, appraisal and behavioral and emotional responses as this chapter will focus on the measurement approaches and will briefly review published measures of such concepts and different measurement approaches. One should note, as discussed in Chapters 1 and 2, that often these cognitive processes are lumped together in a single measure of “perceived stress.”

Introduction

In recent years, interest in the study of stress has expanded, particularly in the disciplines of anthropology and human biology where the focus of research has drifted toward evaluating the adaptive biological, cultural and psychological responses to stressors inherent in everyday living. Field studies of stress in these disciplines have been conducted across a wide continuum of contexts. These range from an assessment of the stress of “modernization” where biological and cultural responses of populations undergoing rapid industrialization/Westernization are examined, e.g. James et al. (1985), to the responses of people facing novel, new environments in modern, Western societies, such as occur in nursing homes (Ice et al., 2002).

Biologically, in studying the stress response, measurements can be made at any of several junctures in the psychophysiological pathways between stressful stimuli and adaptive or pathological outcomes. Measures include emotional/behavioral responses, hormonal variation in the sympathetic adrenal medullary system (SAMS), hormonal variation in the hypothalamic pituitary adrenal axis (HPA), physiological changes in the cardiovascular system and enhanced immune responses. The choice of the most appropriate measure will be determined by a combination of the goals of research, the population of interest and practical concerns. In addition to the particular stress marker(s) chosen for a study, the appropriate sampling strategy and design must be determined. These range from group comparisons of a one-time measure, to ecological momentary assessments, to multiple measures evaluated in a longitudinal design. Some study designs used in stress research require special analytic strategies and sophisticated statistical approaches.

Introduction

The aim of this chapter is to examine measurement issues in the social and cultural study of the stress process. More specifically, the aim is to clarify a methodological orientation that can guide anthropologists and other fieldworkers interested in stress processes within specific social and cultural contexts. As such, this chapter is partly a review of how stress has been measured in many different studies, and partly an examination of the logic of measurement in anthropology and how it can be improved to understand the stress process. The chapter is intended as a supplement to the volume edited by Cohen et al. (1995) that reviewed issues of measurement in studies of the stress. It helps to extend that review in terms of addressing questions pertinent to the study of social and cultural dimensions of the stress process.

Culture and the stress process

In Chapter 1, Ice and James outlined the general conceptual model that guides much of research on the stress process. As they make clear, at one level it can be difficult to separate elements of the process (e.g. when is an environmental challenge an acute or a chronic stressor or when is the emotional state of the individual indicative of a stress appraisal or a coping response?). At the same time, for there to be a sensible measurement model applied to the process, conceptual distinctions need to be made.

In this chapter, I will adhere to the model outlined in Chapter 1, but with a few additions.

Despite the fact that the biological and behavioral responses to the ever-changing conditions in real life define a very important and central component of survival, it is interesting that very few human biological and anthropological researchers include measurements of these responses in their evolutionary study of contemporary humans. The psychobiology of stress, in fact, is often overlooked in evolutionary and ecological studies of human population variation. Part of this oversight may be related to a lack of information on how to study stress under the conditions of real life. This volume will hopefully provide some guidance for researchers interested in expanding their field research to include an assessment of the adaptation to stress.

It is apparent from the contributions to this volume that there are both conceptual and technical issues to consider when evaluating psychobiological adaptation in field studies. As articulated in Chapter 9, researchers need to formulate a plan, and as part of that formulation, carefully determine what is or is not “stressful” in the context of their study. Perhaps a better way of framing this formulation is that the researcher must consider what in the human ecology induces or will induce psychobiological change in their subjects. Chapters 2 through 7 detail the present state of knowledge and current methods of measurement of the cognitive, endocrinological and physiological responses to stress. Each measure has its limitations and many present challenges for field research that are often unimportant in laboratory or clinical settings.

Introduction

Blood pressure is the most familiar and probably the most difficult to interpret measure in anthropological studies of stress and human variation. The difficulty in interpretation arises from the use of single blood pressure measurements as an indicator of stress. The dogma that each person has specific blood pressure numbers that can be used to ascertain pathology (see for example, JNCVII, 2003) has directed the attention of anthropological researchers to the between-individual distribution of these numbers as a means of studying the evolutionary and health effects of stress on blood pressure, and away from the enormous within-individual variation that actually characterizes the adaptive value of blood pressure as it responds to the dynamic stressors of everyday living (James, 1991; Pickering, 1991).

Some 35 years ago, ambulatory monitors were developed which could capture intra-individual diurnal variation in blood pressure (James, 1991). Hundreds of subsequent studies that have employed ambulatory monitoring have shown that a myriad of external environmental stressors, cognitive processes and behavior contribute substantially to the intra-individual diurnal variation in blood pressure. It is this variation that allows people to adapt to the constantly changing challenges that define their everyday life. It is also this variation that is an important contributor to cardiovascular morbidity and mortality. The purpose of this chapter is to outline the issues, methods, and techniques that are related to the study of diurnal blood pressure variation as it occurs in response to the tribulations of everyday life using ambulatory blood pressure monitors.

Stress has been recognized as an important psycho-physiological state since the pioneering work of Hans Selye. But until quite recently it has mainly been perceived in humans as a condition generated by extreme and hostile environments such as going into battle, hospital or academic examinations. Increasingly, however, it has been identified as being a consequence of many aspects of lifestyle and the events of everyday living and that, to varying degrees, large numbers of people experience it. Indeed, from the point of view of long-term health, low-level frequent chronic stress is likely to be much more important than occasional acute episodes.

Chronic stress can hardly be studied by experimental procedures in the laboratory. It clearly needs a population approach with investigators monitoring people in the “field” as they go about their daily business. Psychologists have gained important insights by the design of questionnaires which can be applied not only to particular groups undertaking activities which are deemed to be stressful, such as air traffic controllers, but also to whole populations, experiencing a diversity of lifestyles. They have identified various elements, particularly in occupational situations, which aggravate stress, as for example absence of job control, but questionnaires are of little use outside one's own language, or at least culture. They also have questionable validity in the study of children.

For these wider studies it is necessary, or at least desirable, to have some physiological measures of the stressed state, either of the homeostatic mechanisms which are elicited to control stress or of the morbid consequences of being stressed.