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The original Whitehall Study investigated social determinants of health, specifically the cardiovascular disease prevalence and mortality rates among British male civil servants between the ages of 20 and 64. The initial prospective cohort study, the Whitehall I Study, examined over 18,000 male civil servants, and was conducted over a period of ten years, beginning in 1967. A second cohort study, the Whitehall II Study, examined the health of 10,308 civil servants aged 35 to 55, of whom two thirds were men and one third women. The response rate for Whitehall II was 73% in total, 74% for men and 71% for women. A long-term follow-up of study subjects from the first two phases is ongoing.
The Whitehall cohort studies found a strong association between grade levels of civil servant employment and mortality rates from a range of causes. Men in the lowest grade (messengers, doorkeepers, etc.) had a mortality rate three times higher than that of men in the highest grade (administrators).
The first Whitehall Study compared mortality of people in the highly stratified environment of the British Civil Service. It showed that among British civil servants, mortality was higher among those in the lower grade when compared to the higher grade. The more senior one was in the employment hierarchy, the longer one might expect to live compared to people in lower employment grades.
The first of the Whitehall studies, or Whitehall I, found higher mortality rates due to all causes for men of lower employment grade. The study also revealed a higher mortality rate specifically due to coronary heart disease for men in the lower employment grade when compared to men in higher grades.
The initial Whitehall study found lower grades, and thus status, were clearly associated with higher prevalence of significant risk factors. These risk factors include obesity, smoking, reduced leisure time, lower levels of physical activity, higher prevalence of underlying illness, higher blood pressure, and shorter height. Controlling for these risk factors accounted for no more than forty percent of differences between civil service grades in cardiovascular disease mortality. After controlling for these risk factors, the lowest grade still had a relative risk of 2.1 for cardiovascular disease mortality compared to the highest grade.
Twenty years later, the Whitehall II study documented a similar gradient in morbidity in women as well as men. The name Whitehall II was derived from the previous Whitehall study. The Whitehall Studies revealed this social gradient for a range of different diseases: heart disease, some cancers, chronic lung disease, gastrointestinal disease, depression, suicide, sickness absence, back pain and general feelings of ill-health. A major challenge, and a reason for the importance of these studies, was to understand the causes of this social distribution of so many disorders.
Whitehall II is a longitudinal, prospective cohort study of 10,308 women and men, all of whom were employed in the London offices of the British Civil Service at the time they were recruited to the study in 1985. The initial data collection included a clinical examination and self-report questionnaire. Since then, nine waves of data collection have been completed: phase 1 (1984-1985; age 35 to 55), phase 2 (1989-1990), phase 3 (1991-1993), phase 4 (1995-1996), phase 5 (1997-1999), phase 6 (2001), phase 7 (2002-2004), phase 8 (2006), phase 9 (2007-2009) and phase 10 (2011). The tenth wave began in January 2011, with wave 11 due to begin in January 2012. The study continues to release findings.
The study covers a wide age range, starting at 35 at recruitment and ending at 80 by phase 9:
- phase 1 (age 35 to 55)
- phase 2 (age 37 to 60)
- phase 3 (age 39 to 64)
- phase 4 (age 42 to 65)
- phase 5 (age 45 to 69)
- phase 6 (age 48 to 71)
- phase 7 (age 50 to 74)
- phase 8 (age 53 to 76)
- phase 9 (age 55 to 80)
- phase 10
- phase 11
Research continues to explore the pathways and mechanisms through which social position influences health. The research group aims to build a causal model leading from social position through psychosocial and behavioural pathways to pathophysiological changes, sub-clinical markers of disease, functional change, and clinical disease.
The Whitehall II study began as a study of working age people and investigated the relationships between work, stress, and health. Whitehall II found that the way work is organised, the work climate, social influences outside work, influences from early life, and health behaviours all contribute to the social gradient in health. As participants in this study continue through adult life, the research focuses on inequalities in health and functioning in an aging population. With an increasingly large population of older citizens in the UK, there is an urgent need to identify the causes of social inequalities and to study the long term effects of previous circumstances on people’s ability to function and stay healthy during retirement. Researchers in the Whitehall II team are also considering the role of social inequalities in relation to dementia risk.
The Whitehall II team have a data sharing policy , allowing researchers from other institutions to use data from the Whitehall II cohort. There is a slightly different data sharing policy for projects that involve genetic information. This policy suggests that the team are engaging with the open access movement, a social movement which is gaining momentum in academia.
The social gradient in health is not a phenomenon confined to the British Civil Service. Throughout the developed world, wherever researchers have had data to investigate, they have observed the social gradient in health. In order to address inequalities in health, it is necessary both to understand how social organisation affects health, and to find ways to improve the conditions in which people work and live.
Professor Sir Michael Marmot chaired the World Health Organization's Commission on Social Determinants of Health (CSDH), which was established in 2005 and launched its final report in August 2008. The Commission sought to engage with policy makers, global institutions, and civil society on the issues around health inequalities within and between countries, the social determinants of health, and act to address those issues. The CSDH acted as a catalyst for change, working with countries, academics, and civil society to bring health inequalities to the fore in the national policy dialogue. The overarching goals of the CSDH were to improve population health, to reduce health inequities, and to reduce disadvantages due to ill health.
Health risks associated with disparities of wealth and power
By design, the Whitehall studies have been focused upon a single set of related occupations, where the people within each occupational grade tend to be socially similar, yet clear social distinctions between grades are inherent. The studies were designed in this manner as an attempt to avoid certain research drawbacks associated with generalized social class groupings—drawbacks that otherwise would result from the diversity of occupations within social classes—which in turn would tend to reduce the objectivity of any analysis.
High blood pressure at work was associated with greater "job stress," including "lack of skill utilization," "tension," and "lack of clarity" in tasks assigned. The higher blood pressure among the lowest grade servants was found to be related to the highest job stress score, whereas blood pressure at home was not related to job stress level.
According to Whitehall study researchers, "a steep inverse association between social class, as assessed by grade of employment, and mortality from a wide range of diseases" has been demonstrated. Summing up the moral of the Whitehall studies, the researchers concluded that "more attention should be paid to the social environments, job design, and the consequences of income inequality."
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.
Professor Michael Marmot of the Department of Epidemiology and Public Health at University College London directs the Whitehall II study. Marmot was the commissioner of the World Health Organization's Commission on Social Determinants of Health.
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