Objectives: The association between the amount of standing at work and the progression of carotid intima media thickness (IMT) was studied among 584 active working men participating in the Kuopio Ischemic Heart Disease Risk Factor Study.
Methods: Ultrasound measurements of atherosclerotic changes in the carotid arteries were performed at the beginning of the study and after 4 years. Analyses of changes in IMT included adjustments for risk factors and stratification by base-line levels of atherosclerosis and prevalent ischemic heart disease (IHD).
Results: Significant relationships were found between the amount of standing at work and atherosclerotic progression. After adjustment for the heaviness of the work, psychosocial job factors, income, and biological and behavioral risk factors, the mean change in maximum IMT for those standing not at all, a little, a lot, and very much was 0.24, 0.25, 0.28, and 0.33 mm, respectively. For men with IHD the respective changes were 0.08, 0.15, 0.37, and 0.75 mm -- a 9-fold difference between the no-exposure and high-exposure group. For the men with carotid stenosis, the respective difference was 3-fold.
Conclusions: These findings provide the first empirical support in a population study for the role of hemodynamic factors in the progression of atherosclerosis induced by long-term standing. Men with carotid stenosis or IHD appear especially vulnerable to the adverse effects associated with standing at work. Reducing the duration of standing at work should be considered both in the occupational rehabilitation of such patients and in the primary prevention of atherosclerosis.