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

Abstract

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 (ΔC-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. ΔC-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 ΔC-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, P< 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 μg/24 h, P = 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, P = 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 ΔC-D does not reflect the true WCE.