Methods: Sixteen healthy subjects (25.8±4.4 yrs) performed a standardized experimental acute mental stress task: Paced Auditory Serial Addition Task (PASAT), with 3 trials of 5 min (= one session). Haemodynamic changes were simultaneously recorded during the session (Task Force® Monitor, CNSystems, Medizintechnik AG, Austria). Subject-based scores on 0-10 numeric rating scale (NRS) regarding stress and motivation levels for PASAT were reported at the end of each task trial. These task and measurements were repeated on 3 consecutive days. As control, ten healthy subjects (28.0±1.8 yrs) performed the same task schedule without PASAT.
Results: The correct responses rate of PASAT did not change during the sessions (P>0.485), however, the averaged correct rate of each session (first session: 74±11%) was increased during the second and third session (86±11% and 90±11%, respectively, P<0.001). The subjects kept high motivation scores (7.7±1.9) during the task while the task increased their stress levels (6.7±2.3, P<0.001), however, both motivation and stress levels did not differ between the trials or sessions (P>0.205). Mean RR-interval (939±112 ms) was decreased by PASAT (852±131 ms, P<0.001), however, no change was observed in control (P>0.777). Systolic/diastolic blood pressure (103±10/62±7 mmHg) was increased during PASAT (108±11/69±8 mmHg, P<0.001).
Conclusion: These results showed that repeated PASAT has robust effects on cardiovascular activity and self-reported mental stress levels. It is suggested that PASAT is a valuable tool for evoking acute experimental mental stress and autonomic responses in humans.