Perceived mental stress and reactions in heart rate variability--a pilot study among employees of an electronics company.

In this study perceived mental stress during occupational work was compared to heart rate variability (HRV) using a traditional questionnaire and a novel wristop heart rate monitor with related software. The aim was to find HRV parameters useful for mental stress detection. We found the highest correlation between perceived mental stress with the differences between the values of triangular interpolation of rhythm-to-rhythm (RR) interval histogram (TINN) and the root mean square of differences of successive RR intervals (RMSSD) obtained in the morning and during the workday (r=-.73 and r=-.60, respectively). The analysis shows that as the RMSSD and TINN value differences increase from night to morning, the stress decreases.