A 4-year prospective study of the relationship of different habitual vocational physical activity to risk and incidence of ischemic heart disease in volunteer male federal employees.

A prospective study of coronary heart disease (CHD) was done in 2,635 volunteer male federal employees of postal, health, aerospace, and other agencies, aged 35--59 years at intake. The present analysis is concerned with 2,065 initially well whites, of whom 65 suffered clinical CHD during a 4 years of annual follow-up. The subjects differed markedly in their levels of habitual vocational physical activity, which is classified (1) by division into sedentary, moderate, and heavy activity groups, (2) by blue collar or white collar type of occupation, and (3) by calculated annual caloric expenditure for both vocational and non-vocational physical activities. Intake variables that were studied in relation to physical activity and the CHD incidence include age, serum cholesterol, systolic blood pressure, relative body weight, ECG abnormality, and cigarette smoking. Socioeconomic status (SES) is assessed by levels of education and income and by a combined SES categorization based upon both. Estimated composite CHD risk scores are based upon Framingham equations. The CHD risk factors, singly, as well as in a derived composite risk score, are higher for men with heavy compared to sedentary or moderate habitual physical activity. However, this is a spurious association found to be induced by differences of SES. Thus, when physical activity and SES are studied in a concurrent analysis, a higher CHD risk is significantly associated with lower SES status but not with differences of vocational physical activity. The CHD incidence in this population is studied in relationship both to the risk factors and physical activity by multivariate analysis, using the multiple logistic risk model. The incidence of CHD is significantly associated with age, serum cholesterol, systolic blood pressure, and cigarette smoking. It is not found to be associated with the type of occupation (i.e., blue or white collar), the level of reported habitual vocational physical activity, or the calculated total vocational plus nonvocational caloric expenditure in physical activity.