Tsai Pei-Shan
College of Nursing, Taipei Medical University, Taipei, Taiwan, ROC.
Clin Exp Hypertens. 2003 Oct;25(7):443-54. doi: 10.1081/ceh-120024987.
The prognostic significance of the white-coat effect (WCE) is unclear. Knowledge of the predictors of the WCE may help illuminate the clinical significance of this phenomenon. The purpose of this study was to (i) compare characteristics of subjects demonstrating a WCE, those not demonstrating a WCE, and those demonstrating a reverse WCE and (ii) determine clinical features that may influence the size of the WCE. Forty-one subjects with normotension or mild hypertension who had never been treated with antihypertensive medications were recruited for the study. All subjects underwent a battery of anthropometrical measurements and clinic blood pressure (BP) measurements. To calculate arterial compliance, impedance cardiography was used to measure resting stroke volume in each subject. All subjects performed a laboratory mental stress protocol to determine the size of the BP reactivity. Ambulatory blood pressure (ABP) profiles were studied in each subject with the use of an oscillometric ABP recorder. White-coat effect was determined by subtracting the awake period of the ambulatory systolic blood pressure (SBP) from the clinical SBP. Subjects were grouped according to the size of their WCE. Those who showed a WCE of 5 mmHg and above were assigned to the WCE group; those who showed a WCE of between -5 and 5 mmHg were assigned to the no white coat effect (NWCE) group; those who exhibited a WCE of -5 mmHg and lower were assigned to the reverse white-coat effect (RWCE) group. Subjects with a positive WCE had significantly higher body mass index (BMI) than those without a WCE and those with a RWCE. The WCE group had significantly higher clinic SBP and heart rate (HR) than the RWCE group. Arterial compliance was significantly lower in the WCE group as compared to the NWCE group and the RWCE group. The three groups had comparable ABP profiles. In terms of BP variability, the increase in SBP in response to mental stress did not differ among the three study groups nor did the 24-hour and awake BP variability. For the sample as a whole, clinic HR and clinic-ambulatory SBP difference were higher and arterial compliance were lower in women than in men. Furthermore, clinic SBP significantly correlated with the systolic WCE (r = 0.40, P = 0.009). When men and women were analyzed separately, the correlation between clinic SBP and the systolic WCE was significant in women (r = 0.63, P = 0.001) but not in men (P = 0.95). Multiple linear regression showed that sex (P = 0.013) and clinical SBP (P = 0.003) were the only two variables that significantly influenced the systolic WCE. These two variables together accounted for 29% of the variation in the systolic WCE. In conclusion sex and clinic BP are two major determinants of the WCE. The results of this study indicate that WCE is not related to higher stress reactivity or higher BP variability.
白大衣效应（WCE）的预后意义尚不清楚。了解WCE的预测因素可能有助于阐明这一现象的临床意义。本研究的目的是：（i）比较出现WCE的受试者、未出现WCE的受试者以及出现反向WCE的受试者的特征；（ii）确定可能影响WCE大小的临床特征。招募了41名从未接受过抗高血压药物治疗的血压正常或轻度高血压受试者参与本研究。所有受试者均接受了一系列人体测量和诊室血压（BP）测量。为了计算动脉顺应性，使用阻抗心动图测量每位受试者的静息每搏输出量。所有受试者都进行了实验室心理应激方案以确定血压反应性的大小。使用示波法动态血压记录仪研究每位受试者的动态血压（ABP）情况。白大衣效应通过用临床收缩压（SBP）减去动态收缩压的清醒期来确定。受试者根据其WCE的大小进行分组。那些WCE为5 mmHg及以上的受试者被分配到WCE组；那些WCE在-5至5 mmHg之间的受试者被分配到无白大衣效应（NWCE）组；那些WCE为-5 mmHg及以下的受试者被分配到反向白大衣效应（RWCE）组。出现正向WCE的受试者的体重指数（BMI）显著高于未出现WCE的受试者和出现RWCE的受试者。WCE组的诊室SBP和心率（HR）显著高于RWCE组。与NWCE组和RWCE组相比，WCE组的动脉顺应性显著更低。三组的ABP情况具有可比性。在血压变异性方面，三个研究组在应对心理应激时SBP的升高情况以及24小时和清醒时的血压变异性均无差异。对于整个样本而言，女性的诊室HR和诊室 - 动态SBP差值更高，动脉顺应性更低。此外，诊室SBP与收缩期WCE显著相关（r = 0.40，P = 0.009）。当分别对男性和女性进行分析时，诊室SBP与收缩期WCE之间的相关性在女性中显著（r = 0.63，P = 0.001），但在男性中不显著（P = 0.95）。多元线性回归显示，性别（P = 0.013）和临床SBP（P = 0.003）是仅有的两个显著影响收缩期WCE的变量。这两个变量共同解释了收缩期WCE变异的29%。总之，性别和诊室血压是WCE的两个主要决定因素。本研究结果表明，WCE与更高的应激反应性或更高的血压变异性无关。
