واکنش پذیری قلبی عروقی در تنظیمات واقعی زندگی: اندازه گیری، مکانیسم ها و معنی

Abstract Cardiovascular reactivity to stress is most commonly studied in the laboratory. Laboratory stressors may have limited ecological validity due to the many constraints, operating in controlled environments. This paper will focus on paradigms that involve the measurement of cardiovascular reactions to stress in real life using ambulatory monitors. Probably the most commonly used paradigm in this field is to measure the response to a specific real life stressor, such as sitting an exam or public speaking. A more general approach has been to derive a measure of CV variability testing the hypothesis that more reactive participants will have more variable heart rate or blood pressure. Alternatively, self-reports of the participants’ perceived stress, emotion or demands may be linked to simultaneously collected ambulatory measures of cardiovascular parameters. This paper examines the following four questions: (1) What is the form and what are the determinants of stress-induced CV reactivity in real life? (2) What are the psychophysiological processes underlying heart rate and blood pressure reactivity in real life? (3) Does CV reactivity determined in the laboratory predict CV reactivity in real life? (4) Are ambulatory cardiovascular measures predictive of cardiovascular disease? It is concluded that the hemodynamic processes that underlie the blood pressure response can reliably be measured in real life and the psychophysiological relationships seen in the laboratory have been obtained in real life as well. Studies examining the effects of specific real life stressors show that responses obtained in real life are often larger than those obtained in the laboratory. Subjective ratings of stress, emotion and cognitive determinants of real life stress (e.g. demand, reward and control) also relate to real life CV responses. Surprisingly, ambulatory studies on real life cardiovascular reactivity to stress as a predictor of cardiovascular disease are rare. Measuring the CV response to stress in real life may provide a better measure of the stress-related process that are hypothesized to cause disease than is possible in the laboratory. In addressing these questions, below we review the studies that we believe are representative of the field. Therefore, this review is not comprehensive.

Introduction The highly influential cardiovascular reactivity hypothesis states that individuals showing exaggerated cardiovascular reactivity (CVR) to stress are at higher risk of developing cardiovascular disease (CVD) (Krantz and Manuck, 1984 and Treiber et al., 2003). Most studies of the cardiovascular response to stress are conducted under controlled laboratory conditions. There are excellent practical and scientific reasons for this, centered on issues of measurement, design and control but the laboratory is a particularly difficult environment in which to study stress. There are severe ethical constraints on the nature, severity and duration of the stresses that can be studied in the human laboratory. As a result, most investigations are limited to a rather limited range of predominantly cognitive stressors (reaction time, mental arithmetic, video games, vigilance tasks). Some of these laboratory stressors have a social component (e.g. public speaking). Finally, a commonly used stressor is the rather bizarre, psychologically and physiologically complex, cold pressor test. Participants in laboratory studies are volunteers often fulfilling course requirements and the extent to which the laboratory tasks are experienced as stressful depends to a large extent on how far the participant collaborates with the experimenter and treats the task (e.g. playing a video game) seriously and as personally important. This is perhaps task since the tasks seldom involve significant objective reward or punishment. Such constraints means that laboratory stress tasks may not faithfully represent the stressors that are encountered in real life, i.e. they may have limited ecological validity. Furthermore, cardiovascular (CV) responses obtained in the laboratory may not be representative of the responses seen in everyday live with respect to size, duration or even mechanism. This is different from other areas of psychological study where, for example, it seems likely that the processes of executive function studied in the laboratory represent in a pure form processes that also occur frequently in everyday life. These restrictions on laboratory-based studies of stress are potentially substantial and could severely restrict our understanding of the psychological and physiological processes that underpin CV reactivity and critically limit the potential of laboratory-based CV reactions to predict future disease. In this paper we wish to consider the study of the CV response to stress in everyday life with respect to four questions (1) What is the form and what are the determinants of stress-induced CV reactivity in real life? (2) What are the psychophysiological processes underlying heart rate and blood pressure reactivity in real life? (3) Does CV reactivity determined in the laboratory predict CV reactivity in real life? (4) Are ambulatory cardiovascular measures predictive of cardiovascular disease?

Conclusion The first question addressed in this paper was “What is the form and what are the determinants of stress-induced CV reactivity in real life?” We examined both the situational and the individual determinants of the ambulatory stress response. Studies examining the role of situational factors involve psychosocial stressors, such as giving a speech, undergoing an oral examination, or negative interpersonal interactions can be used as part of a real life stress paradigm. The effects of specific real life stressors can be studied and appear to produce responses that are often larger than those seen in the laboratory. Additionally, subjective ratings of stress, emotion and theoretically important processes that are believed to determine stress (such as demand, reward and control) also relate to real life CV responses. The second question addressed the psychophysiological processes underlying heart rate and blood pressure reactivity in real life. Initial studies examining the hemodynamic processes that determine blood pressure can be measured in real life and the psychophysiological relationships seen in the laboratory can also be seen in real life. The third question was; “Does CV reactivity determined in the laboratory predict CV reactivity in real life?” It appears that averaging over multiple laboratory stressors, due to the effects of both situational and individual factors, does relate to the CV response to stress in real life when that is assessed by examining the response to a objective stressor or by self-reported of experienced stress or the factors that cause stress. Finally, we asked (4) “Are ambulatory cardiovascular measures predictive of cardiovascular disease?” The information that real life studies provide on the strength, mechanisms and frequency of the CVR in real life suggests that it should be a better predictor of future disease than laboratory measures but this is as yet an underexplored area. 6.1. Future directions There has been great progress in the study of the CV effects of stress in real life in the last 30 years, but much remains to be done. Advances are likely to come in four areas; technical, theoretical, empirical and application. Technically there are continued advances in the miniaturization of physiological recording devices and the power of data handling devices such as PDAs and, increasingly smart phones (Morrison et al., 2009). It is now possible to use such phones to obtain self-report data as ratings, text, audio recordings and either store it or have it automatically phoned in. In addition the same devices can establish where the participant is using GPS and features of the environment using audio recordings. The main theoretical question has perhaps remained the same over the years; to determine to what degree the CV response to stress is a product of the person, the situation or, most likely, the specifics of the interaction of these factors. The empirical question, which is closely tied to the theoretical issue of individual and situational factors, is to determine the critical personal characteristics such as race, gender, age and socioeconomic status. The main applied question is, as we have indicated above, to determine if CV response to naturalistic stressors when assessed using the best methods actually predict future disease better than the CV response to laboratory stressors. If, as we hope this is the case, then this opens up new avenues for diagnosis and prevention. If it does not then it is a serious challenge to the reactivity hypothesis.