Good works

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Epidemiology is one of the unsung triumphs of modern medicine since it tells us such important things about ourselves. It examines, in large groups of people with scientific based techniques, the relation between illnesses and environmental factors. At least two surprising results have emerged in the last few years. The first is that babies who do not grow properly in the womb have a high probability of developing heart disease and diabetes when adults. The second relates to psychological factors in the workplace, and several papers have provided further insights into this relationship.

Just over 10 years ago the so-called Whitehall study showed that men in the lower grades of the civil service had nearly three times the risk of coronary heart disease compared to men in the higher grades. Part of this increased risk could be accounted for by conventional coronary risk factors like smoking, but it seemed likely that psychological factors were playing a major role in increasing the risk. Contrary to what might have been expected, high demands at work were not the key factor but, surprisingly, low control appeared to be the key factor. A follow up of the original study confirmed this.

More than 10,000 people were studied with respect to heart disease and amount of control at work. "Job control" means the degree to which an individual can decide how to do their job, what they do at work, choosing with whom and when they work, and how varied the job is. High job demands refers to both intensity and speed, as well as having to combine difficult tasks. For both men and women, low control and low job demands are associated with increased risk - almost twofold - of heart disease.

Research on animals could provide insights into the biological basis of psychosocial factors on health. Baboons, in groups of up to 100, live a happy life requiring only four hours a day to gather food. There is thus lots of time for social activity, and social rank is important and determines access to a variety of benefits. Dominant males, who presumably have most control over their activities, have the greatest concentration of high density lipoprotein in the blood. These lipoproteins rather than cholesterol are probably determinants of risk for heart disease - higher concentrations appear to be protective. It is striking that similar results were obtained when the blood of civil servants was examined.

How could psychological factors so influence body functions? This is a complex area but there is a consensus that the neuroendocrine system of the body is involved. This will come as no surprise as it is well known that the adverse effects of anxiety mediated by the release of adrenaline can be alleviated by beta blockers. And it is not just heart disease that is influenced by stress. Studies on mice, for instance, show that the response of mice to influenza and also tuberculosis is influenced by stress and stress stimulated hormones.

The notion that the mind can affect the body is hardly a new one. What is new is putting the processes on a sound foundation. A combination of epidemiology and neuroendocrinolgy could lead to new ways to improve our health. But there are so many different sorts of molecules involved, and since the nervous system, and the immune system and the hormonal system are all complex, it is going to be tough to make sense of their interactions with each other. Benefits may be a long time coming.