Biology 202
2004 Second Web Paper
On Serendip

In the previous paper, Health: Mind and Society I, we argued that many different variables interact to influence health and disease. Through the principles of psychoneuroimmunology and the biopsychosocial model, we showed that the nervous system is the center of the interactions of these multiple factors (1). The connections and interplay between the neuro-endocrine and immune systems is the physiological basis upon which we will continue our study of how psychosocial factors can, and do, promote poor health. In this paper, we shall explore the biological associations between socio-economic status, stress, and disease. The links between these will shed more light on the social structures and atmospheres fostering such stress, rather than on the physical outcome of disease itself. But first, let us take a look at some of the leading causes of death in our society.

"Atherosclerosis, a disease of the large arteries, is the underlying cause of approximately 50% of all deaths in modern western society" (2). In fact, heart disease is the first leading cause of death in the United States, followed by cancer and deaths from iatrogenic causes (such as unnecssary surgery, medication errors, infections in hospitals, etc.) (3). Therefore, heart and artery diseases constitute a major health concern in our society. It is important to note that these diseases are more prevalent among people from low socio-economic classes. This interesting and distressing finding implies inevitable links between the environment and physical well-being. Besides predisposition, and access to health (or the lack thereof), it is clear that social factors contribute to these significant health problems. "There is a marked socioeconomic gradient in the incidence of CAD [Coronary Artery Disease] such that people of low socioeconomic status, as defined by occupation, education or income, have an increased risk of CAD and acute coronary syndromes" (4). These patterns have also been observed in monkeys. Living in dominance hierarchies, monkeys who are more socially subordinate were found to have higher levels of athersclerosis than the dominant monkeys (5). Given the greater complexities of human society, this may serve as an idea of how powerful socio-political and socioeconomic environments can be in influencing health, and even promoting disease. One can not help but ask whether socioeconomic systems based on cooperation might be healthier than those based on competition and hierarchies. This is only one of many hypotheses that attempt to account for the grave failures of the political and economic structures of our society. In any case, let us now turn to an interdisciplinary research study on socioeconomic status, stress, and its physiological outcomes.

The following study was a collaboration between the Department of Epidemiology and Public Health (Psychobiology Group) and the Department of Medicine at University College London, U.K. (2). Participants were divided into high and low SES (socioeconomic status) groups based on occupation grades. They were then administered two short stress-inducing mental tasks. The two SES groups did not differ at baseline. Yet, the results showed significant differences in the physiological responses to stress in the two groups. Following the test, those in the low SES group had a delayed recovery in blood pressure and heart rate than those in the high SES group (2). "Heart rate increased to the same extent following stress in both groups, however by 2h post-stress, it had returned to baseline in 75% of the high SES group compared with only 38.1% of the low SES group" (2). Another significant difference was in the delayed recovery in interleukin-6 levels experiences by the low SES group, as compared with that of high SES group. "Stress induced increases in plasma IL-6 in all participants, however, in the low SES group, IL-6 continued to increase between 75 min and 2h post-stress, whereas IL-6 levels stabilized at 75 min in the high SES group" (2).

It should be noted that interleukin-6 (IL-6) is a "circulating cytokine" associated with stress (6). Cytokines are chemical messengers which serve in the "bi-directional communication" between the CNS (central nervous system) and immune system. However, excessive amounts of cytokines can be toxic to nerves in the brain (6). Therefore, frequent and prolonged increases in IL-6 levels would have adverse effects on the body. Also, IL-6 stimulates the HPA (hypothalamus, pituitary and adrenal glands) axis. As we have seen in the previous paper, the overworking of the stress and neuro-endocrine responses causes a dampening of the immune system, and a negative outcome on health. Moreover, "HPA hyperactivity is associated with central obesity, hypertension, insulin resistance, and dislipidaemia, all risk factors for CAD" (2).

Thus, taking the results and relevant data, the experimenters came to the following conclusion: People of low SES have a "dysfunctional adaptive response" to psychological stress due to chronic stress-related increases in IL-6 and HPA activity. This chronic stress is understandable if one considers the psychosocial conditions that are more common in low SES groups. The study mentioned such conditions as "the exposure to adverse work characteristics, chronic life stress, social isolation, hostility, depression, and anxiety". All of these factors have been consistently identified as to increasing the risk of cardiovascular disease (2). This highlights again the relevance of the environment and its strong effects on health and the etiology of disease. Moreover, the study adds: "people of low SES tend to be more exposed to sources of chronic stress such as low job control, financial strain, and neighborhood stress, and generally have less social support" (2). Apparently then, the socioeconomic gaps are not such a benign outcome of our capitalist society. This experiment is one of many that have linked SES inequalities to heart disease and other ailments. In fact, longitudinal studies (which follow participants over several years) have also found that chronically stressful environments increase the chances of developing heart disease. Such examples are a small sampling of the accumulating evidence that support the relevance of psychosocial factors in defining and influencing health.

So far, we have seen that considering environmental factors is essential to a better understanding of their important effects on the origin and progress of pathology. Going a step further, and building on the issues raised thus far, the integration of psychosocial socio-political and socioeconomic factors into a broader formula of health should be possible. In the next paper, we will continue to follow the pathological effects of stress-related increases in IL-6. For example high levels of IL-6 have been associated with age-related conditions, general morbidity and mortality (2). We will also explore social isolation and its correlation with HIV progression. As we progress in our study, we become more aware of the role of the environment on our bodies and on our health. Being "social animals", the existence of human being necessarily involves intricate political, economic and social systems. It is more and more evident that these systems could be potential catalysts of disease. Therefore, it is our responsibility to create and monitor systems such that they would cater for a healthy population and society. Indeed, we can build psychosocial protective factors, such as social support and networks. So, perhaps we should consider again the question of an environment based on cooperation rather on competition. Which social structure is more likely to induce malady? And which one would cushion against pathology?

Sources:

1) Psychoneuroimmunology and health psychology: An integrative model, By Erin Castanzo and Susan Lutgendorf. Brain, Behavior and Immunity 17. 2003. p. 225-232.

2) Socioeconomic status and stress-induced increases in interleukin-6, By Brydon, Edwards, Mohamed-Ali et al. Brain, Behavior and Immunity 18. 2004. p. 281-290.

3) Is US Health Really the Best in the World? By Dr. Barbara Starfield. Journal of American Medical Association (JAMA). Vol 284, No. 4. July, 2000. p. 483-485.

4) Social class and coronary heart disease, By Marmot, M. and Bartley, M., in Stansfield, S., Marmot, M. (Eds.), Stress and the Heart. BMJ Books, London, 2002. p. 5-19.

5) Social status and coronary artery atherosclerosis in female monkeys. By Shively, C.A. and Clarkson, T.B. Arterioscler. Thromb. 14. 1994. p. 721-726.

6) The Mind-Body Interaction in Disease. By Esther Sternberg and Philip Gold. Scientific American. 2002.


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