Racial differences in cardiovascular reactivity to mental stress in essential hypertension

Racial differences in cardiovascular and non-cardiovascular sympathetic nervous system (SNS) activity were studied at rest and during an aversive reaction-time task in established hypertensives, borderline hypertensives and normotensive controls. White and black subjects of each group were subjected to 16 signalled reaction time tasks where a 110 decibel (dB) white noise was delivered contingent upon poor performance. During 16 signalled foreperiods (35 s) the following measurements were taken: systolic and diastolic blood pressures, heart rate, respiration-rate and muscle and skin blood flow. Muscle and skin vascular resistances were calculated. Skin conductance activity was recorded as an index of non-cardiovascular SNS-activation. Resting cardiovascular activity was similar in black and white hypertensives and controls, whereas skin conductance activity was greater in white compared to black hypertensives and controls. During the reaction-time task both quantitative and qualitative differences between the races tended to emerge. Heart rate and systolic blood pressure increased less in black patients and controls than in whites. Muscle and skin vascular resistance increased in blacks but was unaffected by behavioural demands in whites. Skin conductance reactivity was attenuated in black patients and controls. Thus, blacks compared to whites show lesser cardiac sympathomimetic responses but enhanced vascular responses to mental stress.