Clinical features, anthropometric characteristics, and racial influences on the 'white-coat effect' in a single-centre cohort of 1553 consecutive subjects undergoing routine ambulatory blood pressure monitoring

Background Patients with high office blood pressures but relatively normal readings during daytime ambulatory monitoring have been the subject of much investigation and debate, This clinical finding in part depends on an aler ting reaction to the circumstances of the clinical measurement, often descr ibed as the 'white-coat effect' (WCE). Little is known of the characteristi cs of patients that are associated with the white coat effect in a large po pulation of routinely referred patients. Objective To relate the size of the WCE (defined as the difference between office and ambulatory daytime readings) to clinical features that may influ ence this phenomenon. Methods We categorized 1553 consecutive subjects (51.3% men, aged 17-88 yea rs), who had been referred to a single centre for the assessment of suspect ed hypertension prospectively into three groups: those aged < 40, 40-59, an d greater than or equal to 60 years. Results WCE on systolic blood pressure (SBP) increased significantly with a dvancing age and was correlated positively to body mass index (BMI), age an d treatment. We found significant correlations to sex (higher in women) and race, WCE on diastolic blood pressure (DBP) decreased slightly with advanc ing age and was correlated positively to BMI and significantly to race and sex, We found no correlation to age or treatment, Caucasians had a greater WCE than did non-Caucasians (P < 0.001 for SEP and DBP) and hypertensives h ad greater WCE than did normotensives (P < 0.0001 for SEP and DBP), Multipl e linear regression analysis showed that age and BMI are the most important factors influencing WCE on SEP and DBP. Conclusions Factors such as race, age and BMI may exert important influence s on the size of WCE possibly via effects on sympathetic nervous system act ivity. (C) 2000 Lippincott Williams & Wilkins.