Autonomic nervous functions and psycho-behavioral factors associated with white coat phenomenon in hypertensive patients

The aim of the present study was to clarify the mechanism of white coat phenomenon by comparing autonomic nervous functions and psycho-behavioral factors associated with the difference between clinic blood pressure (BP) and day-time mean ambulatory BP and those associated with the mental stress- induced BP elevation. We evaluated 86 untreated patients with mild to moderate essential hypertension who had clinic BP>140 mmHg systolic and/or >90 mmHg diastolic on at least 3 visits. Thirty-three males and 53 females were contained, and their ages ranged from 20 to 75 years. Clinic and 24- hour ambulatory BPs were monitored without medication, and the white coat effect was defined as the difference between clinic BP and day-time (6:00- 21:00) man ambulatory BP. After sufficient supine rest, BP and RR interval were recorded beat-to-beat at consecutive sessions of 10 minutes of supine rest, 6 minutes of mental stress by backward counting, and 7 minutes of orthostatic stress. Spectral analyses of the BP and RR interval variability were performed for assessing the sympathetic vasomotor tone (SVT) and the baroreflex sensitivity. In addition, various psycho-behavioral factors were assessed by self-administered questionnaires and semi-structured interview. Then, stepwise multiple regression analyses were performed for systolic and diastolic white coat effects and systolic and diastolic mental stress- induced BP elevations, the independent variables of which were above- mentioned indices of autonomic nervous functions and psycho-behavioral factors. While SVT during mental stress was positively associated with stress-induced BP elevation, SVT during supine rest was negatively associated with white coat effect. While 'Neuroticism', 'Anger' and 'Distorted life style' were positively associated with, and 'Type A behavior pattern' was negatively associated with stress-induced BP elevation, 'Depression' was positively associated with, and 'Maladaptation' and 'Anger' were negatively associated with white coat effect. Furthermore, there were no significant correlations between white coat effects and mental stress-induced BP elevations. In conclusion, white coat phenomenon was regarded as a quite different condition from mental stress-induced BP elevation based on the relevant autonomic functions and psycho-behavioral factors.