AWARENESS OF HIGH BLOOD-PRESSURE INCREASES ARTERIAL PLASMA-CATECHOLAMINES, PLATELET NORADRENALINE AND ADRENERGIC RESPONSES TO MENTAL STRESS

Thirty-six, 19-year-old men within the 95th percentile of mean blood pressure (110 mmHg) at a routine medical screening were randomized into two groups and requested to return for a follow-up visit in 2 weeks. One group was sent a neutral letter, while the other was sent a letter conveying the information that their blood pressures were elevated. After 15 min sitting in the laboratory, there was a significantly higher heart rate (P < 0.05) in the informed group. Thirteen informed and 13 uninformed subjects were examined further by intra-arterial blood pressure recording and serial sampling of arterial catecholamines during cold pressor and mental stress tests. The study was undertaken examiner-blind. Informing the subjects of high blood pressure increased both baseline plasma noradrenaline (P < 0.01) and adrenaline (P < 0.05) and intraplatelet noradrenaline (P < 0.05). Blood pressure (P < 0.05) and heart rate (P < 0.05) increased significantly more in the informed group when the subjects were told of the cold pressor test. In addition, there were exaggerated adrenaline (P < 0.05) and diastolic blood pressure (P < 0.05) responses to mental stress in the informed group. Thus, awareness of high blood pressure in young men may increase sympathetic tone and responses as measured in the laboratory. Conclusions from studies on early pathogenesis of essential hypertension should therefore be drawn with more caution when patients are aware of their high blood pressure.