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Occupation and risk of nonfatal myocardial infarction
P R Hebert1, J E Buring, G T O'Connor
1Channing Laboratory, Department of Medicine, Harvard Medical School, Boston, MA.
Insights
White-collar jobs do not appear to protect against coronary heart disease. The apparent benefit may be due to higher high-density lipoprotein cholesterol levels in these workers.
Area of Science:
- Cardiology
- Occupational Health
- Epidemiology
Background:
- Previous studies suggest a link between socioeconomic status and coronary heart disease (CHD) risk.
- It remains unclear if occupation directly influences CHD or if other risk factors are responsible.
Purpose of the Study:
- To investigate the association between white-collar vs. blue-collar occupations and the risk of myocardial infarction (MI).
- To determine if occupation has an independent role in CHD development.
Main Methods:
- A case-control study involving 230 male MI patients and 222 controls.
- Occupation classified as white-collar or blue-collar.
- Coronary risk factors assessed via interviews; lipid and lipoprotein levels measured from blood samples.
Main Results:
- The relative risk of MI for white-collar workers was 0.74 (95% CI, 0.46-1.19) after adjusting for numerous risk factors.
- This association disappeared (relative risk 0.98, 95% CI, 0.59-1.63) after controlling for high-density lipoprotein cholesterol (HDL-C).
Conclusions:
- White-collar occupation does not seem to offer direct protection against CHD.
- Observed protective effects of white-collar jobs on MI risk may be explained by differences in HDL-C levels.
Background:
While some analytic studies have suggested that individuals in occupations representing higher compared with lower socioeconomic status have a decreased risk of coronary heart disease, it is unclear whether occupation itself has an etiologic role in the development of coronary heart disease or whether differences in as yet uncontrolled coronary risk factors may account for these differences in risk.
Methods:
White-collar vs blue-collar occupation and risk of coronary heart disease was evaluated among 230 male patients hospitalized for a first myocardial infarction and 222 control subjects of the same age, sex, and neighborhood of residence. Information on coronary risk factors was obtained from home interviews, and blood specimens were drawn to test lipid and lipoprotein levels. Usual occupation was dichotomized into white-collar and blue-collar occupation according to the Edwards' classification.
Results:
The relative risk of myocardial infarction of white-collar compared with blue-collar workers was 0.74 (95% confidence interval, 0.46 to 1.19) after controlling for age, cigarette smoking, family history of premature myocardial infarction, history of treatment for high blood pressure, body mass index, history of diabetes, alcohol consumption, type A personality, leisure-time physical activity, total calories, and percentage of calories consumed as saturated fat. However, there was no residual association after control for high-density lipoprotein cholesterol yielding a relative risk of 0.98 (95% confidence interval, 0.59 to 1.63).
Conclusions:
These results suggest that white-collar occupation per se does not appear to protect from coronary heart disease. Any apparent protective effect on myocardial infarction that has been previously observed in white-collar compared with blue-collar workers may be attributable to differences in high-density lipoprotein cholesterol levels.