Vagal cardiac control throughout the day: the relative importance of effort-reward imbalance and within-day measurements of mood, demand and satisfaction

The effects of variables derived from a work stress theory (the effort-rewa rd imbalance theory) on the power in the high frequency (HF_HRV) band of he art rate (0.14-0.40 Hz) throughout a work day, were determined using multil evel analysis. Explanatory variables were analysed at two levels: at the lo west level (within-day level), the effects of positive mood, negative mood, demand, satisfaction, demand-satisfaction ratio, and time of day were asse ssed. At the highest level (the subject level), the effects of sleep qualit y, effort, reward, effort-reward imbalance, need for control, type of work (profession), negative affectivity, gender and smoking on HF_HRV were asses sed. Need for control has a negative effect on HF_HRV after controlling for time of day effects, i.e. subjects with a high need for control have a low er vagal control of the heart. In the long run, these subjects may be consi dered to be at increased health risk, because they have less of the health protective effects of vagal tone. The interaction between effort-reward imb alance and time of day has a positive effect on HF_HRV, i.e, the cardiac va gal control of subjects with a high effort-reward imbalance increases as th e day progresses. It is discussed that this probably reflects reduced effor t allocation, ensuing from disengagement from the work demands. (C) 2001 El sevier Science B.V. All rights reserved.