Whitehall II

Background/Question:

While the Whitehall I study established an inverse association between social class and all-cause mortality, the Whitehall II study investigators sought to study factors that were not previously examined and better defined the degree and causes of the social gradient in all-cause morbidity. Using a new cohort of male and female British civil servants, the investigators looked at differences in employment level and all-cause morbidity. Cardiovascular disease was again of particular interest to the investigators. They also questioned whether the explanation for differences in mortality among differing levels of employment may be related to the susceptibility of workers in lower employment designations to become ill or the clustering of a number of different risk factors such as social circumstances at work and social support networks.

Methods:

Using a prospective cohort model, the investigators recruited 6900 male and 3414 female British civil servants aged 35-55 for a total of 10,314 participants. All participants were working in London offices. [1] Each participant was given a physical exam at his or her place of work, which included an ECG and measures of height, weight, blood pressure and plasma cholesterol. Each participant responded to a self-administered questionnaire that included questions on social and demographic data, health status measures (previous history of CVD, chronic bronchitis, or other long-standing illnesses diagnosed by a physician), job characteristics, social networks and stress level. Participants were also classified based on their level of employment, with Class 1 being the highest (senior executive officer) and Class 6 being the lowest (office support). [1] For analysis, age was standardized and tests of significance were completed in linear regression models. Follow-up data were first taken after 7.5 years, and a number of times following the initial analysis. [1]

Results:

The results of the study revealed little change in exposure to risk factors from the Whitehall I study. Prevalence of cardiac ischemia remained the same, and the inverse association between ischemic heart disease and lower employment level persisted. Women employed in lower level positions also reported a higher prevalence of angina and greater morbidity than men. Obesity, shorter height (indicative of differences in childhood environment), and a family history of heart disease were found to be more prevalent for those in lower level jobs. [1]

Conclusion/Discussion:

The Whitehall II study made a number of conclusions about the observed differences in cardiovascular diseases and causes of mortality. The shorter height of those in the lower employment levels were thought to reflect differences in childhood exposures that may have been critical to the formation of early health habits. The respondents in lower employment levels also felt they had less control over their own health. Social differences in housing and finances also may have contributed to the stress levels of lower employment level respondents, fueling health problems. From a policy perspective, the investigators concluded that the best way to minimize the health differences would be to encourage healthy behaviors across the whole of society, not only among the most privileged. Since publication of the initial findings, a number of other analyses have been performed on the Whitehall II cohort. Over time, the investigators have examined racial differences, lifestyle behaviors, and socioeconomic factors in relation to ischemic heart disease and all-cause mortality. Throughout these analyses, the investigators consistently found a relation with social gradient. Health status progressively worsened from the highest employment classes to the lower classes, thus elucidating the consequences of poorer social environment and income inequality [1]. (HB)