EFFECT OF MENTAL STRESS THROUGHOUT THE DAY ON CARDIAC AUTONOMIC CONTROL

Although many laboratory studies have demonstrated changes in cardiac autonomic control during psychological stress, few have attempted to demonstrate this effect in ambulatory subjects. To address this issue, 24-h electrocardiographic recordings of 33 healthy subjects were analyzed for RR interval and heart period variability (HPV) responses associated with periodic diary entries measuring physical position, negative affect, and time of day. A total of 362 diary entries were made during the 24-h sessions, each in response to a device which signaled on an average of once per hour. HPV was analyzed in the frequency domain, yielding estimates of spectral power in low (LF) and high (HF) frequency bands, as well as the LF/HF ratio.