The white-coat effect is unrelated to the difference between clinic and daytime blood pressure and is associated with greater reactivity to public speaking.

OBJECTIVE: To compare the blood pressure (BP) response to doctor's visit with the BP reaction to a psycho-social challenge and with the difference between clinic and daytime BP (DeltaC-D). SUBJECTS: We studied 64 young stage-1 hypertensive subjects and 33 normotensive controls. MAIN OUTCOME MEASURES: Relationship between direct and surrogate measure of white-coat effect (WCE) and assessment of BP response to public speaking in subjects with normal or increased reaction to BP measurement. METHODS: The responses to BP measurement by a doctor and to public speaking were assessed with beat-to-beat Finapres recording. DeltaC-D was calculated on the basis of two BP monitorings and used as a surrogate measure of WCE. RESULTS: BP and heart rate changes elicited by the visit were unrelated to DeltaC-D and were correlated to the changes caused by the speech test P <0.001 for systolic BP (SBP), P = 0.01 for diastolic BP (DBP), and P <0.001 for heart rate. Hypertensive subjects with SBP response to doctor's visit above the median (hyper-reactive) showed increased reactivity also to public speaking (61 +/- 15 mmHg), while those with BP response below the median (normo-reactive) had a response to the psycho-social challenge (40 +/- 21 mmHg, 0.001 versus hyper-reactive) similar to that of the normotensive controls (38 +/- 17 mmHg). Epinephrine urinary output was greater in the hyper-reactive than the normo-reactive subjects (23 versus 12 microg/24 h, = 0.01). The SBP response to public speaking was greater in the hypertensive subjects with higher systolic daytime BP than in those with lower daytime BP (55.3 +/- 20.9 versus 45.1 +/- 20.6 mmHg, = 0.046). CONCLUSIONS: Subjects with increased WCE have an exaggerated response also to psycho-social stimuli. Average daytime BP, which incorporates the BP reactions to many psycho-social triggers can, thus, not be taken as the basal BP of an individual. This helps explain why DeltaC-D does not reflect the true WCE.