Effects of short-term psychological stress on the time and frequency domains of heart-rate variability

The purpose of this study was to test the hypothesis that short-term psycho logical stress produces significant changes in sympathovagal activity. ii s imple, noninvasive method was used measuring the timing and frequency of he art-rate variability (HRV). 30 normal healthy subjects were assigned into t wo age- and sex-matched groups. In the experimental condition a 5-min. psyc hological stress test, predominantly based on the Stroop Word Color Conflic t Test, was employed in a competitive setting and included a financial indu cement to produce psychological strain. Analysis showed that during psychol ogical stress a significant reduction in the timing and frequency of heart- rate variability was observed. The standard deviation of interbeat interval s decreased. A significant increase in heart rate was also observed. Within the frequency domain, a significant reduction in the high frequency compon ent of HRV and a significant increase in the low frequency component were o bserved. There was also a significant increase in the low frequency to high frequency ratio. Self-evaluation of physical tension and emotional state m easured by visual analog scales also showed significant increases following psychological stress. No significant differences were observed on any vari ables within the control group. The results indicate a shift towards sympat hetic predominance as a result of parasympathetic withdrawal and demonstrat es that this psychological stress test is effective in provoking a characte ristic defence-arousal reaction. This simple, cost-effective method of anal ysing heart-rate variability is suitable for detection of short-term change s in sympathovagal balance.