Mental stress-induced increase in blood pressure is not related to baroreflex sensitivity in middle-aged healthy men

The baroreflex that acts to blunt blood pressure (BP) variations through op posite variations in heart rate should limit the BP increase produced by an emotional challenge. However, relations between baroreflex sensitivity and BP reactivity induced by a psychological stress in a large group of adults have never been firmly established. In 280 healthy men, rest (10 minutes) and stress (5 minutes) BP and heart rate were recorded beat to beat by a bl ood pressure monitor. The mental stress was elicited by a well-standardized computerized version of a word color conflict stress test (Stroop Color Te st). Rest and stress baroreflex sensitivity was assessed by the cross-spect ral analysis of BP and heart rate and by the sequence method. The stress-in duced increase in systolic BP (22.4 +/- 0.1 mm Hg) was not correlated with resting baroreflex sensitivity but was slightly correlated (r = 0.2, P<0.00 1) with BP variability assessed either by standard deviation or by mid-freq uency band spectral power. Our results suggested that a centrally mediated sympathetic stimulation overcame cardiac autonomic regulation and emphasize d the role of the sympathetic vasoconstriction in the pressure response at the onset of the stressing stimulation. During the sustained sympathoexcita tory phase, the cardiac baroreflex blunts BP variations but at a lower sens itivity.