Elsevier

The Lancet

Volume 350, Issue 9073, 26 July 1997, Pages 235-239
The Lancet

Articles
Contribution of job control and other risk factors to social variations in coronary heart disease incidence

https://doi.org/10.1016/S0140-6736(97)04244-XGet rights and content

Summary

Background

The first Whitehall Study showed an inverse social gradient in mortality from coronary heart disease (CHD) among British civil servants-namely, that there were higher rates in men of lower employment grade. About a quarter of this gradient could be attributed to coronary risk factors. We analysed 5-year CHD incidence rates from the Whitehall II study to assess the contribution to the social gradient of psychosocial work environment, social support, coronary risk factors, and physical height.

Methods

Data were collected in the first three phases of examination of men and women in the Whitehall II study. 7372 people were contacted on all three occasions. Mean length of follow-up was 5·3 years. Characteristics from the baseline, phase 1, questionnaire, and examination were related to newly reported CHD in people without CHD at baseline. Three self-reported CHD outcomes were examined: angina and chest pain from the Rose questionnaire, and doctor-diagnosed ischaemia. The contribution of different factors to the socioeconomic differences in incident CHD was assessed by adjustment of odds ratios.

Findings

Compared with men in the highest grade (adminstrators), men in the lowest grade (clerical and office-support staff) had an age-adjusted odds ratio of developing any new CHD of 1·50. The largest difference was for doctor-diagnosed ischaemia (odds ratio for the lowest compared with the highest grade 2·27). For women, the odds ratio in the lowest grade was 1·47 for any CHD. Of factors examined, the largest contribution to the socioeconomic gradient in CHD frequency was from low control at work. Height and standard coronary risk factors made smaller contributions. Adjustment for all these factors reduced the odds ratios for newly reported CHD in the lowest grade from 1·5 to 0·95 in men, and from 1·47 to 1·07 in women.

Interpretation

Much of the inverse social gradient in CHD incidence can be attributed to differences in psychosocial work environment. Additional contributions were made by coronary risk factors-mainly smoking-and from factors that act early in life, as represented by physical height.

Introduction

Inequalities in health are a matter for concern in the UK, USA, and many European countries. In the UK, such inequalities have been labelled “variations”, and have been subject to government enquiry from an NHS viewpoint.1 But the causes and remedies of social inequalities in health go beyond differentials in health services,2, 3, 4 and beyond lifestyle. The first Whitehall study of British civil servants clearly showed an inverse social gradient in mortality from coronary heart disease (CHD); the lower the grade of employment, the higher the age-adjusted mortality rate. About a quarter of this gradient could be explained by social differentials in smoking, plasma cholesterol, blood pressure, height, obesity, and physical activity.5 Better measurement might have explained the gradient further, but much was unexplained by these established risk factors. We proposed that psychosocial factors, particularly related to work, may be important in the generation of the social gradient.6

The Whitehall II study of a new cohort of male and female civil servants was devised to test this hypothesis.7 The job-strain model has been most influential as a method to characterise the psychosocial work environment.8 The model postulates that a combination of high psychosocial demand and low control is related to cardiovascular risk. However, a 1994 review provided only partial support for this two-factor model;9 the control dimension is consistently related to cardiovascular risk, but the demand dimension is not. This finding is consistent with analyses of data for occupational mortality in England and Wales from 1970 to 1972. Occupations characterised by low control were associated with increased CHD mortality, but those characterised by high demand were not.6

Analyses of longitudinal data from Whitehall II confirm the prediction that low control, but not high demand, at work is associated with increased incidence of CHD, independently of measures of socioeconomic status,10 and that low control is associated with higher plasma fibrinogen concentrations.11 Since the importance of low control at work has been established, the purpose of this study was to test the hypothesis that low control makes an important contribution to the generation of the expected social gradient in incident CHD, in additon to the potential contribution made by social supports, height (a possible marker of early life influences), and established risk factors.

Section snippets

study population

The Whitehall II study is based on a cohort of civil servants examined between 1985 and 1988 (phase 1). All male and female civil servants, aged between 35 and 55 years in 20 London-based Civil Service departments were sent an introductory letter and screening questionnaire, and were offered a screening examination for cardiovascular disease. The overall response rate was 73%, though the true rate is likely to be higher because 4% of those on the employee list had moved before the study began,

Results

Table 1 shows the number of men and women by employment grade, the proportion who developed newly reported CHD during the follow-up period, and the odds ratios with high grades assigned a CHD risk of 1. Among men, all three CHD endpoints show an inverse gradient in risk by grade of employment. For the combined endpoint of any CHD event, the odds ratio in the lowest grade compared with the highest was 1–5. Similarly, in women, the odds of developing any CHD in the lowest grade compared with the

Discussion

As predicted, the specific psychosocial work characteristic of low control made an important contribution to the social gradient in incident CHD in the Whitehall II study. We showed previously that low control in the workplace was related-independently of employment grade-to 5-year CHD incidence.10 The analyses given here show that low control is related to employment grade, and appears to account for much of the grade difference in CHD frequency in both men and women. Taken together, these

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