Whitehall Study - Explanations and Implications

Explanations and Implications

Subjects of Whitehall II in the lowest employment grades were more likely to have many of the established risk factors of coronary heart disease (CHD): a propensity to smoke, lower height-to-weight ratio, less leisure time, and higher blood pressure. However, even after normalizing for these factors, the lower employment grades were still at greater risk for a heart attack; another factor was at work.

Some have pointed to cortisol, a hormone produced by the body as a response to stress. An effect of cortisol release is a reduction in the immune system’s efficacy through lymphocyte manipulation. One theory explaining the connection between immune-efficiency and CHD is that infectious pathogens, such as herpes or Chlamydia, are at least partially responsible for coronary diseases. Therefore, a body with a chronically suppressed immune system will be less able to prevent CHD.

A study of the cortisol awakening response (the difference between cortisol levels upon awakening and thirty minutes later) further supports the significance of cortisol. Workers showed no significant difference in cortisol levels upon awakening regardless of socioeconomic position. However, the lower employment grades showed significantly higher levels thirty minutes later, particularly if it was a workday. Researchers concluded this was due to chronic stress and its anticipation.

This seems counter-intuitive: one usually thinks of those with the most decision-making responsibility as the ones with the most stressful lives. One theory is that the lower one is on the chain of command, the less control one has over his or her life. Not having to take orders on how to perform a task, or when to do it, results in lower heart rate, stress hormones, and blood pressure than being told how and when to perform it.

This theory, however, is not without its detractors. A Finnish study conducted a cohort study similar to Whitehall, but with greater analysis of the worker's stress. The study determined that decision autonomy was not a significant contributing factor to coronary heart disease, but that lack of predictability in the workplace was a significant factor. In the Finnish study, "predictability" was defined as high stability of work and lack of unexpected changes, and was found to correlate closely to employment grade.

Others argue that because there is a strong correlation between low employment grade and domestic stress, stress from a lack of control at work cannot be the whole story. In this line of reasoning, the size of one’s paycheck alone could significantly contribute to overall stress. Those with fewer resources have a harder time making ends meet, a situation that can be a tremendous source of chronic anxiety.

Adding to the controversy is the disagreement over the cortisol explanation in the first place. The theory is based on a pathogenic contribution to coronary heart disease and the stressed body’s inability to fight it. Follow-up studies on the Whitehall II cohort failed to demonstrate a correlation between pathogen burden and socioeconomic status, whereas other studies in different parts of the world have.

An alternative to the cortisol explanation is that self-esteem is the major contributing factor and that the link between professional achievement and self-esteem accounts for the health gradient. The study supporting this view correlated low self-esteem in test subjects with greater reductions in heart rate variability and higher heart rates in general—both established coronary heart disease risk factors—while performing stressful tasks.

Currently there is no universally-accepted cause for the phenomenon brought to light by the Whitehall studies. Clearly, stress is associated with a higher risk of coronary heart disease, but so are many other non-traditional factors. Furthermore, “stress” seems to be too nonspecific. There are different kinds of stress in one’s day-to-day life and each kind could contribute differently. Vaananen, et al., are making great headway in this regard by researching which components of stress are responsible and which are not.

Regardless of the exact reason why coronary heart disease is more prevalent in lower employment grades, the results of the Whitehall studies have significantly changed the way some doctors approach the evaluation of heart disease risk. By recognizing the effects of psychosocial stressors on the body, in addition to the traditional risk factors, physicians can offer a better assessment of a patient’s health.