PHYSICAL-ACTIVITY AT WORK AND CARDIOVASCULAR-DISEASE RISK - RESULTS FROM THE MONICA AUGSBURG STUDY

In the MONICA Augsburg study the relationship between physical activity at work, cardiovascular risk factors, incidence of fatal and non-fatal myocardial infarction (MI) and total mortality was investigated in employed men. The MONICA Augsburg baseline survey of 1984/85 was designed as a cross-sectional study with follow-up. Physical activity was determined in 45-64 year old men by interview (n = 1074, 83.6%) and by a 7-day activity diary (n = 797, 62.0%). Employed men were categorized into an active versus inactive group based on interview data on physical activity at work (PA(W)) which had been validated against the 7-day activity diary. When stratified by PA(W), age-adjusted means of diastolic (DBP) and systolic blood pressure (SBP) and total-cholesterol (T-C) were lower and the age-adjusted mean of HDL-cholesterol (HDL-C) was higher in active than in inactive men. A linear regression model controlling for age, body mass index, alcohol consumption, smoking, and heart rate confirmed this relationship for physical activity at work; regression coefficients: DBP: beta = -2.38 (95% confidence interval [Cl] : -3.85- -0.91); SBP : beta = -2.87 (95% Cl : -5.22- -0.52); T-C: beta = -2.80 (95% Cl : -9.31-3.71); HDL-C: beta = 3.48 (95% Cl : 1.28-5.79). Survey participants were followed-up for a period of 5.8 years. The incidence density (per 1000 person-years) of fatal plus nonfatal MI was 6.8 for active men versus 5.9 for inactive men; the incidence density for total mortality was 11.2 versus 5.9, respectively. After controlling for hypertension, T-C and smoking in a Cox proportional hazards model the relative risk of active compared to inactive men was 1.26 (95% Cl : 0.60-2.65) for MI incidence and 1.91 (95% Cl : 0.98-3.73) for total mortality. Adjustment for educational level did not significantly change the relative risks. In spite of the beneficial effect of PA. on cardiovascular risk factors found in cross-sectional analysis, we observed a higher MI incidence and total mortality risk in the longitudinal analyses. The most likely explanation appears to be strong confounding by occupational or social factors.